We have developed transformational, and intrinsically safe, all-solid-state Li-ion batteries (SSLiBs), by incorporating high conductivity garnet-type solid Li-ion electrolytes into tailored tri-layer microstructures, by low-cost solid oxide fuel cell (SOFC) fabrication techniques to form electrode supported dense thin-film (~10mu;m) solid-state electrolytes. The microstrucurally tailored porous garnet scaffold support increases electrode/electrolyte interfacial area, overcoming the high impedance typical of planar geometry SSLiBs resulting in an area specific resistance (ASR) of only ~2 Omega;cm^-2 at room temperature. The unique garnet scaffold/electrolyte/scaffold structure further allows for charge/discharge of the Li-metal anode and cathode scaffolds by pore-filling, thus providing high depth of discharge ability without mechanical cycling fatigue seen with typical electrodes. Moreover, these scalable multilayer ceramic fabrication techniques, without need for dry rooms or vacuum equipment, provide for dramatically reduced manufacturing cost.
Fabrication of supported dense thin-film garnet electrolytes, their ability to cycle Li-metal at high current densities with no dendrite formation, and results for Li-metal anode/garnet-electrolyte based batteries with a number of different cathode chemistries will be presented.

Safe Li-ion battery is critical for success of electric vehicle, and the electrolytes are one of the most important component for the safety of the Li-ion batteries. In this talk, we summarize the research progress of our group on all-solid-state Li-ion batteries and aqueous Li-ion batteries. In all-solid-state Li-ion battery, we report a novel concept of a single-material all-solid-state lithium-ion battery, wherein a single Li₁₀GeP₂S₁₂ serves as an electrolyte, an anode, and a cathode, to eliminate the highly resistive interface between the electrodes and electrolyte. The realization of the single-Li₁₀GeP₂S₁₂ battery is based on the fact that the Li-S and Ge-S components in Li₁₀GeP₂S₁₂ could act as the active centers for lithiation/delithiation as a cathode and an anode, respectively, when electronically-conductive carbon is mixed, while pure Li₁₀GeP₂S₁₂ can be used as an electrolyte. This unique concept of a single-material lithium-ion battery can be extended to other solid-state battery systems, providing a new direction for high-power, high-energy, long-cycling solid-state batteries. For aqueous Li-ion battery, we report a new aqueous electrolyte, whose electrochemical stability window was expanded to ~3.0 V. A full Li-ion battery of 2.0 V was demonstrated to cycle over 1000 times in this electrolyte, with nearly 100% Coulombic efficiency at both low (0.15 C) and high (4.5 C) rates.

Over the last decade, Li-ion batteries have begun to dominate several energy storage markets due to the many inherent advantages of Li-ion chemistry. More recently, a new approach to Li-ion battery technology has been investigated—utilizing solid-state electrolytes made of lithium garnet-type ceramics. (e.g. Li₇La₃Zr₂O₁₂ or LLZ) These materials are inherently non-flammable and contain no toxic or reactive fluorine. Importantly, garnet materials like LLZ are electrochemically stable to Li metal (enabling higher energy density batteries), and are also thermally stable and mechanically strong. The main areas challenging the development of all-solid-state Li-ion batteries, however, have been low ionic conductivity and high interfacial impedance due, in part, to poor solid-solid contact. The ionic conductivity of garnet materials has been steadily increasing as new compositions/dopants are discovered and sintering conditions are optimized. However, if a method existed which could provide precise control over the microstructure, both of the issues could be resolved. First, the thickness of the electrolyte separating the two electrodes could be reduced to the order of tens of microns, such that the overall resistance of the bulk electrolyte would become negligible. Secondly, by tailoring the architecture of the contact surface of the electrolyte with the electrode, the interfacial impedance could be similarly reduced.
With the recent growth and maturation of 3D printing, such precise control over microstructure is now possible, both for scientific and technical applications. Using a 3D printer armed with devices such as a UV lamp for photopolymer spot curing and a laser for laser sintering, not only can the microstructure of the solid electrolyte be adequately controlled, but the interface with the anode and cathode can be modified as well. This presents a distinctive way of quickly fabricating unique, ordered architectures to address the impedance issues described above. Using a 3D printer, thin solid-state batteries have been printed using different microstructures/architectures for each component to explore the effect of each on battery properties. For example, the aspect ratio has been found to significantly impact the performance metrics. Additionally, using characterization tools such as electrochemical impedance spectroscopy, Raman spectroscopy, and SEM, bulk properties and interfacial effects can be investigated with a high degree of accuracy. In this way, both macro and microscopic spatial variations of structure and composition will be probed.

Solid polymer electrolytes (SPEs) possess an inherent safety advantage over traditional liquid carbonate electrolytes, and can be incorporated into an effective solid-state battery at physiological temperature for use in implantable devices. In this work, we report on our progress towards the goal of the development of a solid-state battery utilizing a SPE. The electrochemical properties of a SPE using a poly(ethylene oxide) (PEO) polymer matrix in the presence of tri-ethyl sulfonium bis(trifluorosulfonyl) imide (S2TFSI) ionic liquid (IL) and lithium TFSI with appreciable ionic conductivity ~ 1 mS/cm at physiological temperature are presented. These homogenous, mechanically robust films were fabricated via a hot-pressing method and incorporated into lithium metal/SPE/lithium cobalt oxide or lithium iron phosphate pouch cells where the cycling performance and rate capability were assessed. The cells were disassembled post-mortem and the SPE/cathode interface was examined using a dual FIB-SEM system whereby FIB was used to expose fresh SPE/cathode interface and SEM was used for imaging and elemental composition analysis.

Lithium-ion batteries (LIBs) are one of the most widely used energy storage devices in modern society, and they are playing important roles in the rapidly developing markets of pure/hybrid electric vehicles and other large-scale energy storage systems. Current LIBs utilize flammable liquid electrolytes, which have brought potential risks, especially for large-scale applications. Moreover, additional problems emerge when moving to advanced systems beyond conventional LIBs, such as lithium-sulfur and lithium-air batteries, where the use of metallic lithium as anode would cause dendrite formation and raise safety concerns regarding short circuit. Solid electrolytes have been considered as feasible solutions to the safety issues of liquid ones.
Continuous efforts have been devoted in the past few decades to search new materials for solid electrolytes, which mainly include ceramic-based and polymer-based electrolytes. In this work, a novel class of solid electrolytes with biomimetic ionic channels will be discussed, providing a new direction towards high-performance and robust LIBs.

Thermo-electrochemical cells with aqueous electrolyte that convert low-grade heat (<130 degree Centigrade) directly into electrical energy, has attracted considerable attentions as an alternative strategy to thermal energy harvesting. However, innately poor electrical conductivity of aqueous ferro/ferricyanide electrolyte is one of critical factors to limit the efficiency of thermal-electrochemical cells. In order to enhance electrical conductivity and diffusivity of the electrolyte, applying nanoparticles into the electrolyte which is called electrolyte-based nanofluids can be one of promising ways for the augmentation of mass transport in the electrolyte through the combined effect of percolation behavior and convection. The presence of nanoparticles in electrolyte is seldom studied due to intrinsic instability of nanofluids, especially, in electrolyte with high ionic strength. Moreover, the collocation of base fluids and nanoparticles are strictly restricted by both chemical and physical properties for a stable nanoparticles suspension. Here we report a practicable approach fabricating γ-alumina nanofluid-based ferro/ferricyanide electrolyte equipped with enhanced electrical conductivity and feasible stability by introducing stirred nano-bead milling in conjunction with ultrasonication. Sodium dodecyl sulfate is introduced to stabilize alumina nanoparticles in ferro/ferricyanide electrolyte by constructing steric barriers. 0.2M alumina nanofluid-based ferro/ferricyanide electrolyte holds an ionic concentration 20-fold higher than previous work in the literature, providing practical significance to develop nanofluid-based electrolyte for thermo-electrochemical cells. Based on electrical conductivity and rotating disk electrode studies, the diffusivity of alumina nanofluid-based electrolyte at a nanoparticle mass fraction of 0.25% shows a mutative response to convection, revealing a critical deviation from homogeneous standard ferro/ferricyanide electrolyte at high angular velocities. We decipher this conspicuous increase of the limiting current as a result of both percolation behavior and convection under shear flow. Additionally, alumina nanofluid-based electrolyte is confined by relatively high viscosity, which counteracts to the thermal conductivity. 0.2M alumina nanofluid-based ferro/ferricyanide is demonstrated in thermo-electrochemical cells to capture a progressive figure of merit of 29.9×10^-6K^-1.

A new type of all-solid-state metal-air battery is being developed by the University of South Carolina, based on a reversible solid oxide fuel cell. The operation of this metal-air battery is based on Oshy;^2- conduction, and is able to provide high specific energy and high round-trip efficiency at a temperature as low as 550^oC. However, operation at temperature lower than 550^oC requires a new class of high conductivity catalytic oxide-ion electrolyte. For that propose, a new cobalt-based perovskite oxide with high catalytic activity for oxygen reduction was developed.
Here we report on the surface exchange properties of that new material, SrCo_0.9-xNb_0.1Fe_xO_3-δ, by means of in-situ oxygen isotope exchange. We used our unique heterogeneous catalysis system to determine the oxygen exchange rate coefficients and mechanism for a variety of Fe doping concentrations. Oxygen exchange profiles indicate an enhanced exchange properties of SrCo_0.9Nb_0.1O_3-δ over the other Fe concentrations. Exchange of ¹⁸O₂ reaches a saturation at 450-500^oC, while below 300^oC the exchange is very slow. Fitting the exchange results to a model describing the exchange process we were able to extract the temperature dependence of the exchange coefficient as well as the activation energy for oxygen exchange and compared with the literature data. Reaction order, together with the identity of the oxygen species taking part in the reaction are also investigated through variation in the oxygen partial pressure. The results explicity show an extensive oxygen exchange abiltiy of the electrolyte at intermidiate temperatures.

This work investigates the development of a flexible high potential thin film zinc-air battery by screen printing technique. Commercial Ag ink was used as the anode and cathode current collectors. Polypropylene membrane was used as the separator. 9 M KOH was used as the electrolyte. Mixture of Zn powder, ZnO, and Bi₂O₃ was used as the anode electrode. Types of cathode active materials (carbon paper and carbon black) were investigated. Results showed that batteries using carbon paper and carbon black as active materials provided the open-circuit voltage at 1.44 and 1.45 V, respectively. When batteries were discharged at 0.15 mA/cm², the open-circuit voltage observed from both batteries using carbon paper and carbon black as the active materials were 1.23 V. Battery using carbon black showed a little longer discharging time. Energy density observed from battery using carbon black was 682 Wh kg^-1 and that using carbon paper was 323 Wh kg^-1.

Transparent cathode electrode has been successfully fabricated with microelectrode array pattern using screen printing technique. The result from UV/Vis spectra between 400 to 800 nm indicated that battery with an electrode area of 25 percent (battery A) had transparency of 82 percent, while battery with an electrode area of 20 percent (battery B) had transparency of 86 percent. It can be concluded that transparency of the electrode is inversely proportional to the electrode area percentage. Potentiostat was used to determine the prototype batteries performances. Both battery A and battery B provided the same open-circuit voltage at 1.3 V indicating that the electrode area percentage had no effect on the open-circuit voltage. Both batteries had similar shape of current-voltage characteristic, however, battery A had a flatter slope in the Ohmic polarization region compare with battery B, indicating that battery A could provide more stable current at a given voltage. This was due to higher contact area between the microelectrode array and the electrolyte of the battery A than that of battery B. Nevertheless, further optimization of the battery is still needed in order to make it applicable to be functioned as a transparent energy source for transparent device.

While the double-layered supercapacitors that use carbon materials with high surface areas are commercialized; metal oxide active materials has attracted much more attention in recent years. This is because of their pseudocapacitive behavior; high redox activity and high reversibility. Cobalt oxides (Co₃O₄ and CoO_x) are reported to have high pseudocapacitive properties, which make them promising electrode materials for supercapacitors. Hybrid capacitors using multi-walled carbon nanotubes and cobalt oxides are reported to have high capacitance values; however, research on electrodeposition of cobalt oxide onto single walled carbon nanotube thin films and supercapacitors fabricated by this means with a low-cost route remained elusive.
In this work, single walled carbon nanotube (SWNT) and cobalt oxide hybrid electrodes were prepared and tested. SWNT thin films were fabricated via a low-cost vacuum filtration and consecutive stamping method onto glass substrates and cobalt oxides were electrodeposited from a cobalt nitrate solution. Co₃O₄ phase is obtained by annealing the as- electrodeposited specimen. The capacitive behavior of the hybrid supercapacitors was investigated through cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy. The total charge transfer and Faraday&’s Law were used to obtain the amount of electrodeposited cobalt oxide. A specific capacitance of 230 F/g was obtained at a scan rate of 1 mV/s for the hybrid electrodes. A detailed analysis on the capacitive behavior will be presented in conjunction with the oxidation states and morphology of the active materials.

Supercapacitor devices are complementing batteries with their high power and moderate energy densities. There are commercial batteries that show the remaining battery power through a gauge by means of a thermochromic indicator that measures the heat resistance. Likewise, what if the supercapacitors are made to reveal their stored capacity? One could use electrochromic polymeric materials for this purpose to reflect the stored capacity via color change. A new benzotriazole (BTz) and dithienothiophene (DTT) containing conducting polymer (CP) is emerged as a promising active material both for its electrochromic and electrochemical properties combined in a single device. In this work, we report on the fabrication and characterization of supercapacitors with single walled carbon nanotube (SWNT) and new CP network electrodes. Vacuum filtered SWNT thin films in this work provided high surface area, high conductivity and high transparency for the electrochromic polymer. CP was deposited onto SWNT thin films by drop-casting and experienced multiple color changes with respect to its charged state. Specific capacitance of SWNT/CP nanocomposite electrodes was obtained to be 112 F/g, which was higher than that of bare SWNT electrodes. We will present a detailed analysis of the electrochromic and electrochemical properties of the fabricated supercapacitor electrodes.

Unlike the conventional manufacturing to synthesize nano-silicon with special morphology for lithium ion battery, the peculiar anode material was extracted from the wastes of solar cell industries, which is oversize in micro scale with irregular morphology. Instead of most efforts to avoid the volume expansion, this study demonstrates a multiple surface modifications of atmospheric pressure plasma and carbon overlayer to build a bulwark between electrode and electrode. With different combination of surface modification, the surface chemical bonds of electrode and carbon overlayer were rearranged and nitrogen were revealed to be doped onto the electrode material through the examination of XPS. Raman spectroscope was adopted to verify the ratio of order and disorder of carbon overlayer with/without plasma treatment. The distinct bulwark was formed on the surface which have the function to mitigate the sever formation of solid electrolyte interface (SEI). The enhanced performance was examined between voltage window of 0.05 and 1.2 V with stable retention and high Coulombic efficiency. Through the analysis of cyclic voltammetry and AC impedance, the electrochemical properties were evaluated with the insertion/extraction behavior and internal circuit resistances. Furthermore, the etching profile of XPS interpreted the difference in multiple surface modifications, and provided the evidence of the bulwark after first cycling. Finally, the combination of plasma treatment and carbon layer gives the waste with a new life for potential application.

Silver ferrite, AgFeO₂, exhibits a layered delafossite-type structure with the general chemical formula ABO₂. A low-temperature, aqueous co-precipitation reaction employing non-stoichiometric ratios of starting materials, AgNO₃ and Fe(NO₃)₃, was developed allowing for the manipulation of composition (Ag_xFeO₂, 0.2 le; x le; 1.0) and crystallite size (10-18 nm). The composite nature of the low silver materials as a combination of crystalline silver ferrite, AgFeO₂, and non-crystalline maghemite, γ-Fe₂O₃, was established by Raman spectroscopic and X-ray absorption analyses. The layered structure of delafossites enables ion transport and a limited number of literature reports describe exploration of silver delafossite oxides as cathodes in lithium-based batteries, including an investigation of AgCuO₂ and AgCu_0.5Mn_0.5O₂. Studies of AgFeO₂ demonstrated that stoichiometric silver ferrite, with an Ag : Fe ratio of 1 : 1 and an average crystallite size of 31 nm, is electrochemically active. As a cathode, the low silver content composites (x = 0.2) exhibited significantly enhanced electrochemical performance with capacities approximately100% higher relative to stoichiometric AgFeO₂ and demonstrated the lowest capacity fade. The synthetic approach demonstrated herein provides a new paradigm for composite synthesis, offers an economically feasible method to prepare electrode materials, and is applicable for industrial scales. This research can be applied to viable electrode materials to increase the efficacy and energy density of modern battery technologies.

The lithium-carbon monofluoride (Li/CFx) battery system exhibits desirable battery characteristics of high energy density (exceeding 2000 Wh/kg), long shelf-life, and low self-discharge. These batteries have been utilized in a wide range of applications including implantable medical devices, portable communication devices, and military and aerospace electronics. However, the broader application of Li/CFx batteries has been limited by their power capability. Multi-walled carbon nanotubes (CNT) are appealing additives for high-power batteries, due to their outstanding electronic conductivity, long aspect ratio necessitating low volume fraction for percolation and high flexibility. This summary describes the current state-of-the-art in Li/CFx batteries and highlights opportunities for development of high-power LI/CFx batteries via utilization of CNT. In our research, we investigated the resistivity of CFx combined with CNT and compared the CFx-CNT composites with conventional carbon additives. We investigated CFx-CNT electrodes without metallic current collectors and compared their electrochemical performance with conventional CFx electrodes using metallic current collectors. Furthermore, we fabricated multilayered CNT-CFx-CNT electrodes (sandwich-structure electrodes) and studied the influence of structure on performance of the electrode. By generating several electrode architectures using CFx-CNT combinations and investigating the impact of CNT on the electrochemical performance, we demonstrated the opportunities for utilization of CNT in CFx electrode and the promising implementation of CFx electrode in next-generation high-power batteries.

The unique structural architecture of carbon-based nanoporous structures such as activated carbon (AC) has made activated carbon one of the most viable materials to address current environmental challenges. The highly developed porosity, large surface area, tunable surface chemistry, and high degree of surface reactivity make AC the most widely used adsorbent for the removal of wide variety of organic and inorganic pollutants dissolved in aqueous media or from gaseous environments, as well as the use as electrodes in energy related applications. Traditional feedstocks for AC production include, primarily, mineral carbons, and lignocellulosics from biomass and wood. However, any cheap material, with a high carbon content and low mineral content, can be used as a precursor for the production of AC. Agricultural wastes are proving to be promising precursors for the production of ACs mainly due to their availability, low cost and zero carbon foot print. We present preliminary investigation on utilized mechanical ball milling followed by chemical activation technique to convert agricultural waste (cocoa and coconut husks, palm midribs and calabash) into ultra-high surface area activated carbon suitable for myriads of environmental and energy related applications. Our preliminary investigation indicates about 70% increase in BET surface area with ball milling to as high as ~ 3000 m²/g, and shows potential application as electrode material in supercapacitors.

Multilayer films of Graphene-Chitosan nanoplatelets with glucose oxidase were assembled using the layer-by-layer (LbL) technique. The aim here is a better comprehension of how the presence of Graphene-Chitosan (G-Chitosan) nanosheets present in the LbL nanostructured multilayers influences the direct electron transfer process between enzyme and electrode. The LbL assembly was chosen due to its simplicity and versatility to produce thin films with controllable thickness and morphology, taking the advantage of nanoscale engineering to create tailored architectures that can hold the enzyme inside the multilayers formed, with fine control in the film composition and structure. The G-Chitosan choice was based on the possible biological compatibility and possibility to support a direct electron transfer (DET) mechanism between active center inside the enzyme and the electrode. Here, UV-vis was used to investigate the film formation and also the structure of the enzyme immobilized, which was also characterized by potentiometric measurements to check the DET process. Our results indicated good adherence and linear growth of the (G-Chitosan/Gox) LbL films, and also a DET dependence on the film structure. In summary, we believe that the LbL multilayer assembly facilitates the DET as some nanoplatelets are becoming closer to the active center of the enzymes.

WSe_2shy; is used for the first time as a sodium ion battery anode and shows a high capacity of 253 mAh/g at a rate of 10 mA/g during the first sodium extraction. This is comparable to or higher than other commercially available transition metal dichalcogenides (TMDs). WSe₂ is compared to WS₂ and demonstrates a higher specific performance, better rate capability, and less capacity fade. WSe₂ also shows a small overpotential of 0.25 V between the anodic and cathodic peaks which is promising for practical applications. Ex situ Raman spectroscopy, X-ray diffraction, and energy dispersive x-ray spectroscopy in the transmission electron microscope show the formation of a crystalline product with domains containing either selenium or tungsten, suggesting a conversion reaction mechanism that differs from MoS₂. This work demonstrates that WSe₂ is a promising material for use as an electrode in sodium ion batteries and we identify further routes, such as controlled nanostructuring, as a means to further improve the measured performance and cyclability.

A hollow TiO₂ was synthesized through hydrolysis of titanium tetraisopropoxide in order to facilitate lithium ion insertion into and extraction from the TiO₂ bulk. The pore size hollow TiO₂ is ca. 40-100 nm with controllable wall thickness, for example, from 9 to 23 nn. The as-obtained hollow TiO₂ with 13 nm wall thickness delivered an initial capacity of 255.9 mAh g^-1 with an initial Coulombic efficiency of 72.8% at a current density of 10 mAh g^-1. After two cycle activation, the hollow TiO₂ anode was cycled at a current density of 200 mA g^-1, exhibiting a capacity of 170.9 mAh g^-1 at the 3rd cycle and a slightly increased capacity of ca. 176 mAh g^-1 in the subsequent cycles due to the further activation of TiO₂. The porous TiO₂ shows excellent cyclic performance; after 200 cycles, the capacity remains at 161 mAh g^-1, 91.5% of the highest capacity at 200 mA g^-1. The hollow TiO₂ also exhibits very good rate capability. The capacities are 254, 221, 207, 187, 173, 160, 136, and 114 mAh g^-1 for the current densities of 10, 20, 40, 100, 200, 400, 1,000, and 2,000 mA g^-1, respectively. The capacity of 114 mAh g^-1 obtained at 2,000 mA g^-1 corresponds to 44.9% and 51.6 % of those obtained at 10 and 20 mA g^-1, respectively, indicating an excellent rate capability. Considering the excellent cyclic performance of the hollow TiO₂, long-term cycling was performed at 400 mAh g^-1 for 1,500 cycles, delivering 167 mAh g^-1 while retaining 83% of the reversible capacity. In conclusion, the as-prepared hollow TiO₂ possesses particle sizes of ca. 100 nm and thin wall thickness, which facilitates lithium ion insertion and extraction to allow the hollow TiO₂ to deliver high capacities, excellent rate capability, and distinguished cyclic performance; therefore, the TiO₂ anode is very promising for practical applications

In order to enhance the sustainable development of our economy and society, efforts have been made to explore new compositions or to design novel nanostructures for energy storage materials. Rechargeable lithium-ion batteries (LIBs) is one of the promising candidates. Among the available electrode materials for the Li-ion batteries, magnetite (Fe₃O₄) is regarded as an appealing material due to its high theoretical capacity, natural abundance as well as environmental friendly. Herein, we report a green and facile one-step method to decorate the graphene foam with uniform mono-dispersed Fe₃O₄ colloidal nanoparticles at room temperature. The as-synthesized hierarchical Fe₃O₄/graphene anode material exhibited a large reversible specific capacity (~950 mA h g^-1 at 100 mA g^-1), excellent cyclic stability (nearly unchanged after 200 cycles), good rate capacity and high Coulombic efficiency. This excellent electrochemical performance of Fe₃O₄/graphene hierarchical structures should have a great potential to be used as an active electrode for lithium-ion batteries. Moreover, such safe, cost-effective and straightforward fabrication process provides a new methodology to design and synthesize high performance anode materials for smart electrochemical energy storage systems.

Manganese oxides are one of the most promising transition metal oxide materials for pseudo-capacitor, battery, catalysts, biosensor, magnetic materials and ion-exchanger because of their excellent electrochemical properties. Among them, nanostructured manganese dioxide (MnO₂) have attracted great attention due to the high theoretical capacities, abundance, environmentally friendliness, low cost, and good electrochemical properties. MnO₂ exists in several polymorphic forms such as α-, β-, γ-, δ-, and lambda;-types. Among them, great attention has been paid to δ-MnO₂—a layered birnessite-type—due to its large capacitance and high ionic conductivity. Owing to significant relationship among the crystal structure; specific surface area; and specific capacitance, a variety of synthesis methods have been applied to obtain optimal structures of MnO₂. However, multi-step process, time-energy consuming and expensive additional reagents still seem to be obstacles for the commercialization of the nanostructured manganese oxide. In this study, birnessite-type MnO₂ was synthesized from potassium permanganate (KMnO₄) aqueous solution by adding simple-inexpensive sugar D-glucose in the solution before generating glow discharge plasma, at room temperature and atmospheric pressure. To control structural properties of the synthesized MnO₂, the frequency conditions were varied as 15, 25, 35 and 45 kHz. As the frequency was increased, processing time was shorten from 15 to 5 min. Differentiation of the synthesized MnO₂ were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) method, and Raman spectroscopy. Crystallinity and specific surface area of the synthesized MnO₂ were successfully controlled by the discharge conditions. These findings suggest that solution plasma process is an effective method to control the optimal structure of nanostructured MnO₂.

A non-aqueous aprotic Li-air battery is a promising device for future energy management systems, because Li-air batteries can potentially exhibit much higher energy density than today&’s Li ion batteries. Development of electrocatalysts for the oxygen evolution reaction (OER) in aprotic Li ion electrolytes accompanied with Li₂O₂ decomposition is a critical challenge to be addressed toward the realization of rechargeable Li-air batteries with high round trip efficiency. One approach to overcome this inherent problem with electrocatalysts is to use a soluble catalyst that can repeatedly adsorb on the growing or dissolving Li₂O₂ front. However, the solubility of the catalyst used so far was less than several millimoles per liter, which would prevent further improvement of the charging performance.
In this study, we demonstrates that the tert-butyl cobalt phthalocyanine (tb-CoPc) and analogues serves as a soluble catalyst on the positive electrode for rechargeable Li-O₂ batteries. The cell containing tb-CoPc displayed superior charging performance, exhibiting the potential of about 3.3 V at the initial stage of the charging process. Importantly, the superior discharge/charge processes accompanied with reversible formation and decomposition of Li₂O₂ indicated that tb-CoPc function as OER catalyst without changing the reaction scheme.
The effect of tb-CoPc addition on the discharge/charge characteristics was investigated using a coin type cell. Although both cells showed a stable discharge potential at around 2.7 V, there is a clear difference between the charging profiles. For the cell without tb-CoPc, the charging potential was around 4.0 V and then finally reached ca. 4.3 V. In contrast, the cell with 10 mM tb-CoPc exhibited better charging performance. To confirm the effect of the high solubility of tb-CoPc, the effect of CoPc addition, which has lower solubility than tb-CoPc due to the lack of tert-butyl-groups, was investigated. The solubility of CoPc in the representative Li-ion electrolyte that was used (i.e., 1 M Li trifluoromethanesulfonate dissolved in triethylene glycol dimethyl ether (TEGDME)) was not more than 1 mM. Notably, the redox potential of tb-CoPc is more negative than that of CoPc, which is also advantageous for the charging process. However, the charging performance was not so improved when the concentration of tb-CoPc is 1 mM, indicating that the improved charging performance in the presence of 10 mM tb-CoPc is mainly due to the higher solubility of tb-CoPc compared with CoPc.
In conclusions, we have demonstrated that tb-CoPc functions as a soluble catalyst on the positive electrode for rechargeable Li-O₂ batteries. The results obtained here reveal the importance of an appropriate design for the soluble catalyst in rechargeable Li-air batteries to achieve high round-trip energy efficiency.

Lithium iron phosphate (LFP) has been proposed in 1997 by Padhi et al. [1] as a cathode material for lithium ion batteries. It is a cheap, environmentally friendly and prone to build batteries with very long lifetimes, since the electrochemical potential of LFP ist well inside the stability window of most liquid electrolytes. The material has since been subject to a lot of research and is widely commercially available, however, the mechanism of lithium insertion and depletion is still under discussion [2-4]. Batteries consist of many parts and usually contain a multitude of active materials and additives. In order to avoid overlapping effects or side reactions, detailed studies of a material require a reduced complexity. Thin films are one approach in reducing the complexity of systems. Due to the short diffusion paths, thin films usually do not require conducting additives. Furthermore, a smooth surface is a well defined area in comparison to rough or even porous particle samples.
In this study thin films of carbon-free LiFePO₄ with a thickness of about 200 nm have been prepared on silicon substrates by pulsed laser deposition. From these thin films we build electrochemical cells with 0.1 M LiBOB in a 1:1 mixture of EC/DMC electrolyte and a lithium anode.
The cells were used to perform Galvanostatic intermittend tittration technique (GITT) measurements. From the data obtained by this technique it is possible to calculated the diffusion coefficients of single-phased systems from the change of the equilibrium voltage with the lithium concentrations. In the case of the two phase system LFP this should in principle not work, because the equilibrium voltage for different concentrations of lithium should be constant.
However, the GITT measurements on our samples showed that the equilibrium voltages indeed depends on the lithium concentrations. This implies a single-phase material at the surface of the thin film. Therefore, the analysis with the GITT equation was possible and the diffusion coefficients were determined to be between 3#8901;10^-12 cm²s^-1 to 8#8901;10^-12 cm²s^-1. We present a model to explan our findings.
[1] Padhi, A. K.; Nanjundaswamy, K. & Goodenough, J., Journal of The Electrochemical Society, 1997, 144, 1188
[2] Srinivasan, V. & Newman, J., Journal of The Electrochemical Society, 2004, 151, A1517
[3] Malik, R.; Abdellahi, A. & Ceder, G., Journal of The Electrochemical Society, 2013, 160, A3179-A3197
[4] Delmas, C.; Maccario, M.; Croguennec, L.; Le Cras, F. & Weill, F., Nat Mater, 2008, 7, 665

Li-ion capacitors (LICs) recently gained much attention because they combine both high power density of supercapacitors and high energy density of lithium-ion batteries. In these work, we propose a high performance LIC based on etched silicon anode material that was synthesized by metal-assisted chemical etching technique. The physical properties of etched silicon are analyized by SEM, BET, XRD, XPS, and TEM. Prior to full cell assembly, the etched silicon is lithiated to 0.01 V vs Li/Li⁺ and then is paired with high surface area activated carbon as the cathode, polypropylene as separator and 1.3 M LiPF6 in ethylene carbonate and dimethyl carbonate (3:7 volume ratio) as electrolyte. The full cell was then subjected to several electrochemical analysis including cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic cycle test at different current density. The results show that the LIC based on the etched silicon is able to remarkably retain nearly 90% of its initial capacitance even after 50,000 cycles at high current density. The improved electrochemical performance is attributed to the structural design of silicon anode, which provides a porous material, thereby increasing the specific surface area of anode, promoting an easy electrolyte access and accelarating the Li-ions diffusion.

Tin(Sn) and its alloys have been attracting attentions as a negative electrode material for lithium-ion and sodium-ion secondary batteries with high theoretical capacity (Li₂₂Sn₅, ca. 990 mAh#65381;g^minus;1) and high electromotiveforce. There still remains the issue as regards the discharge capacity decrease with increasing the number of cycles. In order to improve cycle performance, there are many studies such as using Sn-Ni alloy, macroporous patterns and enhancing adhesiveness of active materials. However, most of these studies are using Sn based alloy as negative electrode materials and it suffer from the disadvantage of lowering of discharge capacity. In this study, a deposition process for making Sn film which consists of amorphous structure for negative electrode of lithium ion secondary batteries utilizing electordeposition from aqueous bath was developed. The effect of additives on the surface morphology and microstructure of Sn film was investigated. Furthermore, we evaluated the effect of amorphous structure in the Sn film on cycle performance of the Sn negative electrode. The Sn film was formed by electrodeposition using aqueous bath at low temperature. Cu foil with a thickness of 35 mu;m was used for the substrates We used 5 types of Sn deposition bath. Tin sulfate (SnSO₄) and tin chloride (SnCl₂) were used as metal resource reagents. Phosphinic acid (H₂PO₂), boric acid (H₃BO₃) and potassium sulfate (K₂SO₄) were used as additives. In addition, conventional Sn deposition bath, which consists of 30 g L^minus;1 (0.14 M) tin sulfate (SnSO₄), 96 g L^minus;1 sulfuric acid (H₂SO₄) and 100 ppm polyethylene glycol (PEG, Mw: 4000), was used for comparison. Both amorphous and crystalline structure was observed in the deposited Sn film. In contrast to conventional Sn electrodeposited film, this unique Sn film has a good cycle characteristic (>50 cycles) and discharge capacity (> 400 mAh#65381;g^-1). Furthermore, in the case of using the bath which includes phosphinic acid (H₂PO₂) in composition discharge capacity after first cycle approached over 700 mAh g^-1 and that of after fifties cycle was over 400 mAh g^-1. Amorphous structure in the Sn film showed a microscopic effect on the volume change by lithiation and delithiation.

Electric double layer capacitor (EDLC) has been attracted much attention as one of the most promising high power and durable energy storage devices. However, low energy density is the major drawback, therefore, the optimization of active carbon specific surface area, mesoscale pore volume and electrostatic capacity should be necessary.
In this study, we prepared thermosetting resin (phenol resin and furfural resin, 10 mm in diameter)-based active carbon particles in N₂ atmosphere in three hour (temperature rising rate: 10C /min) at 6000C. Then we treated those samples by three kinds of methods, KOH activation (KOH: samples = 4: 1 in weight), CO₂ activation or a combination of KOH and CO₂ activation. All activation methods were carried out for 30 minutes at 8000C (temperature rising rate: 100C /min). Specific surface area/pore size distribution measurement was carried out using N₂ adsorption. We prepared two coin-shaped carbon electrodes (as working and counter electrodes, 14 mm in diameter), and investigated the electrostatic characteristics of the capacitors in 6M KOH to elucidate the relationship between physical and electrochemical properties.
We obtained phenol resin based active carbon having large specific surface area, 1253 m²/g and 1240 m²/g, by KOH and KOH+CO₂ activation methods, respectively, however, we could not only by CO₂ activation method (515 m²/g). The volumic mesopore ratio of KOH, KOH+CO₂, and CO₂ activation methods were 8.4, 12.8, and 8.8, respectively. Using CO₂ activation did not result in specific surface area development, however, CO₂ activation after KOH treatment increased mesopore ratio with keeping large specific surface area. In all activation methods, electrostatic capacity improved with increasing specific surface area.
Specific surface area of phenol resin derived carbon particles was almost the same by both KOH and KOH+CO₂ activation methods, however, electrostatic capacity after CO₂ activation was improved from 109 F/g to 163 F/g at 20mA/cm². The same trend was also observed with the cases of furfural resin derived carbon particles. The best electrostatic capacity of activated carbon particles from phenol resin and furfural resin were 163 F/g and 119 F/g at 20mA/cm², respectively, in this study

We fabricated three-dimensional metal foam for current collector of positive electrode and demonstrated a high electrochemical performance of lithium iron phosphate batteries. Electrode was made by filling LiFePO₄ into 600 µm pore size and 1000 µm thick Al metal foam. As a result of applying 5, 6, 7, 8, 9, 10 mA to 10 cycled single, double and triple stacked electrode, 5 mA of triple and double stacked electrode showed highest capacity which was 130 mAh/g. and single electrode showed low capacity, approximately 113 mAh/g. C-rate gets lower because double and triple stacked electrode have much more active material mass. But by measuring 60 cycles to 10 mA, the coulombic efficiency of single, double and triple layer cell was 50, 35, and 30 %, respectively. Triple layer cell showed lowest capacity which was 40 mAh/g. When it cycles while increasing current, Lithium diffusion distance gets longer as electrode becomes thicker. So lithium cannot diffuse from inner part to surface and get stacked inside.

Here we design a nanostructure by embedding Au nanoparticles into ZnO/NiO core-shell composites as supercapacitors electrodes materials. This optimized hybrid electrodes exhibited an excellent electrochemical performance including a long-term cycling stability and a maximum specific areal capacitance of 4.1 F/cm² at a current density of 5 mA/cm², which is much higher than that of ZnO/NiO hierarchical materials (0.5 F/cm²). Such an enhanced property is attributed to the increased electro-electrolyte interfaces, short electron diffusion pathways and good electrical conductivity. Apart from this, electrons can be temporarily trapped and accumulated at the Fermi level (EF') due to the localized schottky barrier at Au/NiO interface in charge process until fill the gap between ZnO and NiO, so that additional electrons can be released during discharge. These results demonstrate that suitable interface engineering may open up new opportunities in the development of high-performance supercapacitors.
Acknowledgement
This work was supported by the National Major Research Program of China (2013CB932602), the Major Project of International Cooperation and Exchanges (2012DFA50990), the Program of Introducing Talents of Discipline to Universities, NSFC (51232001, 51172022, 51372023, 51372020), the Research Fund of Co-construction Program from Beijing Municipal Commission of Education, the Fundamental Research Funds for the Central Universities, the Program for Changjiang Scholars and Innovative Research Team in University.
Reference:
[1] Ellis, B.; Knauth, L., Three-Dimensional Self-Supported Metal Oxides for Advanced Energy Storage. Adv. Mater. 2014, 26, 3368-3397.
[2] Zheng, X.; Sun, Y.; Yan, X.; Chen, X.; Bai, Z.; Zhang, Y., Tunable Channel Width of A UV-Gate field Effect Transistor Based on ZnO Micro-Nano Wire. RSC Adv. 2014, 4, 18378-18381.
[3] Lu, X.; Zhai, T.; Zhang, X.; Shen, Y.; Yuan, L.; Hu, B.; Gong, L.; Chen, J.; Wang, Z., WO₃-x@Au@MnO₂ Core-Shell Nanowires on Carbon Fabric for High-Performance Flexible Supercapacitors. Adv. Mater. 2012, 24, 938-944.
[4] Liao, Q.; Mohr, M.; Zhang, X.; Zhang, Z.; Zhang, Y.; Fecht, H., Carbon Fiber-ZnO Nanowire Hybrid Structures for Flexible and Adaptable Strain Sensors. Nanoscale, 2013, 5, 12350-12355.

Lithium-ion batteries (LIBs) have been extensively developed in the recent years, owing to its high energy density and excellent cycle life. As an important representative of the class, LIBs have been widely used in portable electronics such as electronic equipments, mobile products, and communication devices.
Separator plays an important part in lithium-ion battery. Polyolefin separators such as polypropylene (PP) and polyethylene (PE) are one of the most widely used separators of lithium-ion battery, because polyolefin separator have good mechanical properties, chemical stability and effectively prevent thermal runaway caused by electrical short-circuits or overcharging. However, they do not readily adsorb the electrolyte solvent due to their hydrophobic surface with low surface energy, and have poor ability in retaining the electrolyte solutions and therefore often require a modification of their surface properties before use.
To overcome these disadvantages of polyolefin separators, various methods including the modification of polyolefin separator, preparation composite separator, and development of new materials used for separator, plasma treatment and physical/chemical vapor deposition have been developed to improve hydrophilicity of the polyolefin separator. Surface modification by plasma is the green process to modify the surface of the polymeric materials.
In this study, the surface of PE separator was modified by oxygen plasma treatment for high-performance lithium-ion battery. The changes of surface morphology were observed by using Field Emission Scanning Electron Microscopy (FE-SEM). The chemical composition of the surface was analyzed using X-ray photoelectron spectroscopy (XPS) and Attenuated total reflection infrared spectroscopy (ATR-IR). Oxygen plasma treatment improved a variety of properties of PE separator such as the electrolyte retention, the electrolyte wettability, and high ionic conductivity. In addition, the electrochemical characteristics of plasma-modified PE separator showed the improved charge-discharge test, and the cells showed stable cycling performance. The results indicated that the plasma-modified PE separator qualifies as a potential application in lithium-ion battery.

Lithium batteries are important devices and several different anode and cathode combinations have been studied to enhance storage capacity, cyclability, and other characteristics.
Vanadium pentoxide (V₂O₅.nH₂O) is a very useful material for lithium batteries cathodes, displaying good conductivity, capacity storage, easy to synthesize and it has a lamellar structure allowing ions intercalation. Due to different types of Li+ intercalation sites, it is common to observe structural modifications during charge/discharge cycles assigned to structural stress which leads to irreversible Li+ trapping inside this matrix, decreasing its storage capacity.
Cucurbit[n]urils (CB[n]) are a family of hollow toroidal macrocycles obtained by condensation of n glycoluril units and formaldehyde. Our group have intercalated CB[7] into the interlamellar gap of lamellar double hydroxides (LDH) and we could show that the macrocycle works as a pillar, supporting and maintaining the lamellar structure.
We have intercalated a series of macrocycles into V₂O₅.nH₂O such as CB[6], CB[7] and HCB[6] to act in a same way avoiding rearrangements, however, the carbonyl oxygens of both portals seem to trap Li+ ions by themselves. To solve this problem, we have pillarized the structure with a CB[6] vanadyl complex (CB[6]VO), where a VO²⁺ ion avoids Li+ coordination.
The presence of CB[6]VO into V₂O₅.nH₂O stabilizes the oxide structure avoiding rearrangements and offers alternative pathways for lithium ions diffusion.
References
[1] F. de A. Silva, F. Huguenin, S. M. de Lima and G. J. F. Demets, Inorg. Chem. Front. 2014, 1, 495.
[2] G. J. F. Demets, Quim. Nova, 2007, 30, 1313-1322.
[3] L. F. S. da Silva, G. J. F. Demets, C. Taviot-Guého, F. Leroux and J. B. Valim, Chem. Mater., 2011,23, 1350-1352.

Medium-to-large scale energy storage systems require battery technologies comprising both abundant, low-cost materials and inexpensive fabrication methods. Na-ion batteries (NIB), often considered a potential successor of the lithium ion battery (LIB) technology for medium-to-large scale systems, can approach the energy and power densities of current state-of-the-art battery technologies while significantly reducing material and fabrication cost. A variety of possible NIB chemistries have been successfully demonstrated, in most cases, however, material design and fabrication have followed the cost-intensive approaches of the LIB technology. Here, we report on the development of NIB electrodes, taking into consideration not only performance criteria, but also material and manufacturing cost. Both anode (carbon composite) and cathode (layered metal oxide) were fabricated by ultrasonic spray pyrolysis, a solution-based, easy-to-scale process. Structure and composition were studied using tip-enhanced Raman spectroscopy, scanning electron microscopy, and X-ray diffraction. Electrochemical performance was evaluated in half-cell (vs. Na) and full-cell configuration by analyzing cell impedances, charge-discharge voltage profiles, rate performance, and cycle life.

New high-energy density battery systems are needed to elevate energy densities beyond that of Li-ion batteries, particularly if we are to meet increasing energy storage demands worldwide. Certainly the chemistry paths beyond lithium-ion systems are large and portend immense opportunities. One key approach in targeting new chemistries/systems is to employ lessons learned from lithium-ion battery technology. Indeed the evolution of lithium batteries has originated from redox intercalation chemistry which is based on inserting lithium ions into empty crystallographic sites of a host material and exchanging equivalent charge with via transition metal redox couples [1]. The same concept could also be extended to insert bi- or tri-valent ions in the place of monovalent ions inside the host material and thereby increasing the number of electrons exchanged in the host material [2]. While the multivalent concept has merit and is strongly pursued, unless higher voltage oxide-based cathodes can be employed, then development of high-energy multivalent systems is hindered. Essentially oxide host materials are severely plagued by slow solid-state diffusion of multivalent ions inside the lattice due to stronger interaction of multivalent ions compared to monovalents. Additionally the integration of such cathodes into the full battery is hampered due to incompatibility with electrolytes. In comparison with other multivalent ion species (e.g. Mg²⁺, Ca²⁺, Al³⁺ and Y³⁺), the pursuit of non-aqueous Zn²⁺-ion intercalation chemistry has been limited, primarily by its unattractive low oxidation potential. However, thanks to some recent positive improvements in non-aqueous Zn²⁺-ion electrolytes, our group has embarked on systematic studies related to Zn-ion intercalation properties of various oxide host materials and this presentation will cover the latest developments. A number of important physico-chemical parameters will be explained and reported, such as redox potentials, number of electrons exchanged and structural transformations upon intercalation/de-intercalation phenomena. Design rules and comparisons of Zn²⁺-ion intercalation properties to that of Mg²⁺-ion will be discussed as well.
References
1) M. S. Whittingham, Chem. Rev., 2004, 104, 4271.
2) J. Muldoon, C. B. Bucur, T. Gregory, Chem. Rev. 2014, 114, 11683.
3) E. Gocke, W. Schramm, P. Dolscheid, R. Schollhorn, J Solid State Chem., 1987, 70, 71.
Acknowledgments
This work was supported as part of the Joint Center for Energy Storage
Research, an Energy Innovation Hub funded by the U. S. Department of Energy, Office of Science, Basic Energy Sciences. Work done at Argonne and use of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy Office of Science by Argonne National Laboratory, were supported by the U.S. Department of Energy under Contract No. DE-AC02-06CH11357

Among the entire battery family, lead acid (LA) batteries, nickel metal hydride (NiMH) batteries, and lithium ion batteries (LIBs), have great potentials for terrestrial and non-terrestrial electrochemical energy storage applications. Among all the above mentioned energy storage devices, Li ion batteries have received intensive research and development focus because of their high energy density, long cycle life, and superior environmental friendliness. Performance of Li-ion battery has to be improved for satisfying the requirements of advanced technologies like plug in hybrid electric vehicles (PHEV) and hybrid electric vehicles (HEV), in which high energy storage devices are essential. Li₂MnO₃ based composite cathode materials are capable of providing better electrochemical performance than layered, spinel or olivine cathode materials as their structure-stabilizing components provide better stability. Also when they are charged above 4.6 V, a very high value of specific capacity is obtained. These characteristics are enormously attractive for high energy Li ion batteries. But the irreversible capacity loss is a retracting factor for these types of cathode materials. We synthesized Li₂MnO₃ based composite cathode material with layered LiNi_0.66Co_0.17Mn_0.17O₂ and LiNi_0.5Mn_0.5O₂. Our main aim is to reduce the use of cobalt as much as possible and make the cathode material safe and economic. Surface characterization proved the phase formation, crystalinity, size, and presence of constituent particles in the as prepared composite cathode material. Electrochemical characterization shows improved cathode performance in terms of rate capability test and cyclability tests. Cyclic voltametry studies and electrochemical impedance spectroscopy studies confirmed the potential applicability of the composite cathode material for Li ion battery technology. To understand the effect of Co concentration in the cathode material we will present a comparative study on the performances of composite cathode material with and without LiNi_0.5Mn_0.5O₂.

A demand for grid energy storage systems is increasing for extensive deployment of renewable energy such as solar and wind systems. Scalable energy storage with low cost will be a key to meet these challenges.
Non-aqueous Lithium-polysulfide(Li-PS) flow batteries are of particular interest due to their scalability, high potential chemistries, and potentially low cost for grid storage applications.
While top-down models for Li-PS flow battery have been developed, they have not examined in detail the electrochemical performance and materials cost using bottom-up approach.
Here we present a comprehensive assessment of system cost analysis for nonaqueous Li-PS flow battery and the model examines the correlation between performance and cost as considering the physical property limitations of the system components and manufacturing.
Additionally, the comparison with enclosed Li-ion system allows a deeper understanding of the design phase space for the requirements of an application

Although Zinc Bromine (Zn-Br₂) secondary batteries have been studied for decades as a low cost, fully rechargeable, high density energy storage system, the large scale and widespread commercial implementation of this technology has not yet been realized due to two key limitations: i) Self-Discharge: Elemental bromine, Br₂ (l) generated during the charging cycle tends to convect and diffuse through the aqueous zinc bromide electrolyte to the Zn counter electrode, thus self-discharging the cell. ii) Zinc Dendrites: Repeated electroplating and dissolution of zinc during charging/discharging of the cell leads to the formation of dendrites, which can grow to eventually form a conductive bridge from the anode to the cathode and short-circuit the cell. [1] Zn-Br₂ flow-cells alleviate these limitations by adding bromine complexing agents and by flowing electrolyte to reduce Zn dendrite formation, respectively, albeit at the cost of cell resistance, battery efficiency, size, and capital costs. [2]
In this work, we demonstrate a simple, low-cost, non-flowing Zn-Br₂ cell design, possibly without the use of complexing agents. We discuss strategies for local containment of Br₂ (l) by leveraging its unique physical chemistry as well as using innovative electrode design.
The prevention of undesired Zn dendrite formation issue is addressed by using a nano-structured Zn electrode which has a more uniform growth front compared to dendritic Zn. The formation of nano-structured Zn is described elsewhere [3]. Our model test cell consists of 18 mL of 2M ZnBr₂ aqueous electrolyte which yields specific charging capacities of 155.6 and 138.8 mAh/g of electrolyte at current densities of 1.0 and 5.0 mA/g, respectively. The discharge specific energy of over 100 Wh/kg at 5 mA/g is recorded, with a Coulombic efficiency of over 90%. This is a high capacity battery considering that the cost of all the materials going into the cell is $39.50/cell inclusive of passives. Unlike traditional Zn-Br₂ systems we do not use a pump. The electrochemical characteristics of this non-flowing Zn-Br₂ cell are further discussed in terms of cell resistance, specific capacity, energy and coulombic efficiencies, and cycle life. Finally, we provide a novel visible light method for examining the current distribution and bromine concentration within the cell.
References:
[1] P.C. Butler et al. Handbook of Batteries,Ed. 3, Ch. 39, McGraw-Hill, Ohio (2001)
[2] D. Ayme-Perrot et al., J. Power Sources (2008) 175, 644
[3] M. Chamoun et al., NPG Asia Materials (2015) 7, e178

Electrochemical capacitors (ECs) use a very different charge storage mechanism than batteries, relying on the physical adsorption of ions on a high surface area material instead of chemical reactions. ECs can yield a power density of more than 10x that of batteries, however, they provide about 10x less energy density. Since the energy density of the device is proportional to the square of operating potential window, an effective way to increase energy density of the device is by increasing this voltage window. Theoretically, ionic liquid electrolytes can operate at up to 6 V, though experimentally, the value is between 3-4 V, depending on the properties of electrode materials. Though they boast a large operating potential window, ionic liquids are known to contain large and bulky ions. This can make it difficult to use an ionic liquid on a porous carbon with a range of pore sizes, even though the specific surface area of the electrode material is higher. It has also been shown that the capacitance of porous electrodes is maximized when the ion size is matched to the pore size.¹ In this case, the ion is small enough to fit inside the pores and the entire pore volume is used efficiently.
Therefore, we have studied the relationship between the electrode and electrolyte when designing a high performance EC, specifically focusing on the interface of the IL electrolyte at the carbon. By designing an electrolyte based on mixed ionic liquids, ² we can match the ions in the mixture to the multiple pore sizes of the electrode material. Different porous carbons with varying pore size distributions are used to illustrate the effect of ionic liquid mixture electrolytes. While it is possible to tune the carbon electrode to the electrolyte³, such as in carbide-derived carbons, it is much simpler to design an electrolyte mixture that will optimize the performance of a conventional electrode material, such as activated carbon. We show that by tuning the electrolyte to the electrode material, the operating voltage window of the device can be expanded by about 1 V, thereby greatly increasing the energy density. We explore the possibility of substantially increasing the EC&’s performance by designing the appropriate electrolyte to replace the currently used flammable organic electrolytes that operate in a very limited temperature and voltage window.
1. Lin, R. et al. Solvent effect on the ion adsorption from ionic liquid electrolyte into sub-nanometer carbon pores. Electrochim. Acta54, 7025-7032 (2009).
2. Van Aken, K. L., Beidaghi, M. & Gogotsi, Y. Formulation of Ionic-Liquid Electrolyte to Expand the Voltage Window of Supercapacitors. Angew. Chemie127, 4888-4891 (2015).
3. Largeot, C. et al. Relation between the Ion Size and Pore Size for an Electric Double-Layer Capacitor. 2730-2731 (2008).

Sodium-ion batteries have been shown to be a potential alternative for energy storage. It is also found that iron disulfide (pyrite) exhibits high reversible capacity and cycling stability in sodium batteries. Iron disulfide is earth-abundant and environmental-friendly, being an excellent candidate to incorporate with future development of renewable and sustainable energy. In order to understand the structural evolution during the charge/discharge processes in batteries, and hence to design sodium-ion batteries with higher capacity and high charge/discharge rates, visualization the structure and probing the chemical sates of the material are of importance. In this study, natural pyrite is used in the sodium battery for study the structural evolution during the charge/discharge process. A 20 um thick natural pyrite disc was mounted as the anode in a button-type battery cell with sodium as the cathode. The electrolyte was 1M NaPF6 in EC/PC (1:1). The cell was discharged first, and then charged again to intercalate sodium ions into the iron disulfide anode. In TEM analysis, amorphous structure was formed in the iron disulfide anode. The uniform contrast and smooth morphology resembles that of Si nanowires charged with lithium ions. Energy-dispersive spectroscopy elemental maps show uniform distribution of iron and sulfur; the atomic ratio of them is 1:2, as the stoichiometry of iron disulfide. Sodium is also distributed uniformly in the charged anode. Oxygen also appears in the specimen in TEM, indicating strong oxidation of sodium in the anode.

There has been an increasing demand for lithium-ion batteries with higher energy density, longer cycle life, lower cost, and environmentally friendly operation. Si nanoparticles have been considered to be one of the promising anode materials because of its high specific capacity. However, huge volume expansion during battery operation hinders the application of Si anode. This problem could be alleviated through modifying the structure of Si nanoparticles. In this report, recent results will be described on modifications of Si, phosphorus doped Si and carbon coated Si nanoparticle using carbon additive. The capacity and cycle life are shown to exhibit significant improvement. One example involves graphene, which is electronically conductive and mechanically strong. Si nanoparticles - graphene nanosheets are also investigated to create spaces to adjust the volume change of Si nanoparticles during lithiation and delithiation. Results from XRD and TEM characterizations of the morphology changes before and after cycling will also be discussed.

Silicon nitride coated silicon (N-Si) was synthesized by two-step DC sputtering on Cu Micro-cone arrays (CMAs) at ambient temperature. The electrochemical properties of N-Si anodes with various thickness of nitride layer were investigated. From the potential window of 1.2 V to 0.05 V, high rate charge-discharge and long cycle test were executed to investigate the electrochemical performances of various N-Si coated Si-based lithium ion batteries anode materials. Higher specific capacity can be obtained after 200 cycles. The cycling stability was enhanced via thinner nitride layer coating as silicon nitride films were converted to Li₃N with covered Si thin films. These N-Si anodes can be cycled under high rates up to 10 C due to low charge transfer resistance resulted from silicon nitride films. This indicates that the combination of silicon nitride and silicon can effectively endure high current and thus enhance the cycling stability. It is expected that N-Si is a potential candidate for batteries that can work effectively under high power.

Ionic Liquids have been a promising alternative to solvent-based synthesis for a variety of materials due to their attractive wide temperature window and scalability potential. Ionic Liquid medium for use in synthesis of crystalline active cathodic material had been recently explored, though precursor solubility remains a long-time issue. In this approach, water is initially used as solvent for formation of intermediates, enabling effective precursor solubility. Formed intermediates are then fully reacted in ionic liquid medium, enabling ease in synthesis through water-assistance in solubilization. With use of aqueous solvents for intermediate formation, solubility product can be employed to drive precursor toward intermediate phases for continued reaction in ionic liquid medium. Reported here are solubility product observations for the solubilization / reprecipitation of intermediates along with its direct effect on active LiFePO₄ product crystallinity, morphology, and electrochemical performance in further steps.

Hydrogen is a very promising fuel source due to its high mass-specific energy and wide applicability. However, hydrogen must be pressurized before being transported, stored, and used. Unfortunately, the compression of hydrogen gas is very energy intense, significantly decreasing the efficiency and increasing the cost of hydrogen systems.
Thermodynamic studies have shown that producing hydrogen in pressurized chambers could reduce the energy losses due to compression and raise system efficiency. Most of these studies are purely analytical, however, and ignore practical limitations. The goal of this work is to demonstrate and test a safe high-pressure electrolysis system for hydrogen production at 5000 psi. An experimental setup has been fabricated and its functionality to compress liquid water, split the compressed water at 5000 psi by electrolytic reaction on mesh-type electrodes, and release the generated hydrogen at this high pressure has been shown.
Appropriate materials for the electrodes have been investigated and their feasibility of their use at very high pressure is demonstrated.

The stability of nonaqueous electrolytes against reduced oxygen intermediates (O^2-bull;, LiO₂, O₂^2-, LiO₂^-, etc.) generated on air-cathodes during discharge process is one of the main barriers for the practical applications of Li-O₂ batteries. Recently, highly concentrated electrolytes have been reported to greatly improve the stability of Li metal anode and the cycling performance of Li-S batteries.^[1,2] In this work, we systematically studied the effect of salt concentrations in electrolyte on the cycling performance of Li-O₂ batteries with common carbon nanotubes based air-electrodes. We found that CNTs-based electrodes with 3M electrolyte delivered enhanced cycle stability under full discharge/charge for 40 cycles, and no capacity loss under discharge/charge depth (1000 mAh g^-1) for 55 cycles. In contrary, the cycling of these electrodes with 1M and 2M electrolytes appeared significant decline during discharge/charge processes. The compositions and morphologies of the air-electrodes and Li-metal anodes before and after cycling have been systematically analyzed. The stability of the various electrolytes was also analyzed by computational simulations. The new insights that dual-protection derived from high concentration electrolyte for both air-cathodes and Li-metal anodes have been disclosed. The detailed results and discussions about this study will be presented.
Acknowledgements
This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, of the U. S. Department of Energy (DOE) as part of Battery Materials Research program. The microscopic and spectroscopic characterizations and computational calculations were conducted in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the DOE&’s Office of Biological and Environmental Research and located at PNNL.
[1] J. Qian, W.A. Wesley, W. Xu, P. Bhattacharya, M. Engelhard, O. Borodin, J.-G. Zhang, Nat. Commun. 2015, 6, 6362.
[2] L. Suo, Y.-S. Hu, H. Li, M. Armand, L. Chen, Nat. Commun. 2013, 4, 1481.

Recnet progress in fiber-based supercapacitors has attracted tremendous attention due to the tiny volume, high flexibility and weavability of the fibers, which are required for the development of high-performance fiber eletrodes. The unconventional electronics, which can conformably deform into complex shapes under bending, stretching, compressing, twisting process while maintaining good performance, reliability and integration, have opened a promising prospect of future devices. In recent years, flexible energy-storage devices have attracted tremendous attentions due to their potencial in integration into stretchable and wearable eletronics. Fiber based supercapacitors have been of particular interest because of their integration of lightweight, high flexibility and tiny volume, which are favorable for portable applications. However, supercapacitors usually suffer from much lower energy density, limiting their practical applications. Therefor, it is essential to enhance their energy densities for the development of fiber based supercapacitors. Solid electrolytes, apart from providing mobile ions without a liquid, can prevent undesirable short circuit of the two electrodes without the need for a membrane separator. In additon, some solid electrolytes can bind to fiber eletrodes to enhance their mechanical flexibility. Solid eletroytes do not have the leakage problem experienced in liquid electrolytes. Thus, they can simplify the device packaging process and reduce decice device volume.
In this work, a low-cost high-performance solid-state flexible symmetric supercapacitor with MnO₂ nanoflakes grown on flexible carbon fibers (CF) is designed and fabricated. The carbon fibers serves as highly conductive backbones for deposition of nanostructured MnO₂, which provide the high accesibility of electrolytic ions for shorten diffusion paths. An all-solid-state flexible supercapacitor based on a MnO₂/CF fiberstructure has been developed on the basis of the intrinsic mechanical flexibility of CF. The solid-state flexible summetric supercapacitor shows a typical capacitive behavior with nearly rectangular CV curves and discharge curves are almost symmetrical to the corresponding charge curves, indicating excellent reversibility and good charge propagation between the two fiber electrodes. With the contribution of pseudocapacitance of MnO₂ nanostructures, the all-solid-state fiber supercapacitor shows the much enhanced electrochemical capacitive behaviors such as a high energy density of 0.20 mWh/cm³ which is much higher than that of SWCNT-based symmetric SC (0.01 mWh/cm³) and TiN symmetric SC (0.05 mWh/cm³). Furthermore, our fiber-based flexible supercapacitor also shows a good rate capability, excellent flexibility and high long term cyclability, which makes it a promising power source for flexible energy-related devices.

The Advanced Research Projects Agency (ARPA-E) funds high risk, high reward transformational research to reduce energy related emissions, reduce imports of energy from foreign sources, improve energy efficiency across all economic sectors, and ensure US technological lead in advanced energy technologies, including electrochemical energy storage and transformation for grid scale and automotive applications.
This presentation will give an overview of the electrochemical energy storage and transformation portfolio at ARPA-E including past and ongoing focused programs as well as OPEN FOA projects. A diverse set of programs includes development of transformational batteries, flow batteries and fuel cells on both cell and system level. Possible approaches for significantly increased performance, long cycle life and reduced cost will be discussed.
Cost reduction of energy storage systems is paramount for mass adoption of electric transportation and wide deployment of intermittent renewable energy sources. A trade-off between high battery specific energy and complicated system level designs to ensure safety levels the gains in energy density. The ARPA-E Robust Affordable Next Generation Energy (RANGE) program takes an alternative approach to reduce the safety related vehicle weight via development of inherently safer chemistries and structurally functional architectures. In energy transformation area, the ARPA-E&’s Reliable Electricity Based on Electrochemical Systems (REBELS) program targeting distributed generation for more reliable and flexible smart grid focuses on intermediate temperature fuel cells that operate between 200-500^oC .
This presentation will also highlight flow battery technologies including funded by ARPA-E. Flow batteries seem to be a viable alternative to traditional batteries with stationary electrodes due to the decoupling of power and energy, which could lead to multiple applications with the same chemistry, long living homogeneous liquid electrolytes and easy scaling. Current trends and research needs in the flow batteries materials development will eb analyzed. A comparison of organic and inorganic active materials in aqueous and non-aqueous electrolytes for flow battery applications will be presented. Compatibility and selection of active materials, electrocatalysts and membranes will be covered.

Reliable, high-performance lithium-ion batteries (LIBs) are highly desired for advanced electronic devices, electrical vehicles (EVs), and grid energy storage. While the energy density, power density and cycling life of LIBs have been significantly improved during the past two decades, battery safety, an equally critical issue, has yet to be fully addressed. Current safety strategies are mainly based on external devices or systems, which suffer from slow response. Some internal safety devices have been reported, but their application is limited by high room-temperature resistivity, small operation voltage window and/or large current leakage. There remains a strong demand for safety solutions from inside of the battery. Here, we report a fast, reversible thermo-responsive switching electrode that can effectively prevent battery thermal failure events. We fabricated hybrid composite films with high electrical conductivity (σ, up to 5000 S/m) at room temperature. The σ decreases by 7~8 orders of magnitude at high temperature in < 1 s and returns to high values at room temperature. Batteries with these films can rapidly shut down at abnormal conditions (e.g., overheating, shorting), and resume normal functions without performance compromise. Our method offers 10³~10⁴ times higher sensitivity than previous switching devices, and provides a simple and effective strategy to control battery safety.

As batteries are used in increasingly larger formats and larger packs, safety is becoming a primary concern as small defects in manufacture or use in overcharge conditions can lead to catastrophic failures. Detection of in-situ health conditions can inform battery management systems of internal dysfunction such as penetration of the separator by lithium dendrites - uninhibited, this can lead to short-circuiting, fires, and even explosions. A multifunctional separator is an ideal platform for health sensing, particularly the detection of dendrite growth as information about the dendrite passage through the separator can be converted into a voltage signal which can be recorded by the battery management system. This detection scheme can serve as an early warning system for conditions which may develop into safety hazards and allow for early implementation of safe shutdown. The detection of hazardous conditions is critical for the safe deployment of lithium-ion batteries for new and existing applications. Other potential detection schemes will also be presented.

The current state of the art in the research field of the mechanical behavior of electric vehicle (EV) batteries is limited to quasi-static analysis. The lack of published data in the dynamic mechanical behavior of EV batteries prevents engineers from exploring bold design concepts, such as multifunctional batteries used as a part of crash energy dissipating structural members of EVs improving the vehicle safety. In such a multifunctional battery design, EV batteries can be designed as kinetic energy dissipation device to mitigate the risk of bodily injury to the vehicle occupants during collision while utilizing the vehicle crumple zone as a very large storage space for batteries, rather than protecting batteries behind the steel cage, in order to increase the driving range of EVs. Our research has to size scales on this topic: a) energy dissipation at the cell and pack levels and b) energy dissipation at the vehicle system level. For a) cell and pack level analysis, we utilized finite element (FE) numerical approach with lower-scale laboratory data as input to predict the behavior of battery cells under various loading conditions. Then, the FE numerical results were compared against the cell and pack level experimental results to confirm the validity of the study. For b) vehicle system level analysis, the results of the cell and pack level analysis were used to develop the homogenized material models for battery packs. Then, the mechanical properties of the homogenized material were used in FE vehicle analysis to understand the effectiveness of the proposed model against the vehicle crash data obtained from National Highway Traffic Safety Administration (NHTSA) database. Safety, weight saving, and driving range are some of the key topics that contribute to the high market penetration of EVs for today&’s increasing need for sustainable energy in transportation. This study aims at these high-level objectives through effective use of the large amount of batteries on an EV in multi-functions.

The need to create a next-generation electrochemical energy storage (EES) device partially arises from the unending safety threat posed courtesy of the flammable electrolytes and oxygen-releasing cathodes innate to lithium-ion batteries—our modern-era&’s ubiquitous EES device. With international restrictions coming (or here) that limit shipping lithium-based batteries as air cargo, “beyond lithium” takes on new resonance for EES research. Zinc-based batteries offer a compelling alternative thanks to nonflammable aqueous electrolytes augmented by the high earth-abundance of Zn and an energy density comparable to or greater than Li-ion. The performance of traditional Zn-based batteries is hindered, however, by suboptimal Zn utilization (typically <60% of theoretical capacity in Zn-air cells) and poor rechargeability—thanks to the complex dissolution/precipitation processes that accompany Zn/Zn²⁺ cycling in alkaline electrolytes. We have adapted the design advantages inherent to three-dimensional (3D) battery architectures [1-3] to address these limitations for zinc anodes. Reconfiguring the zinc anode as a monolithic, porous, highly conductive, and 3D-wired “sponge” rewrites its EES performance. When discharged in primary Zn-air cells, Zn sponge architectures achieve >90% Zn utilization while retaining the 3D monolithic framework and a cell impedance characteristic of the metal [4]. The structural characteristics of the Zn sponge also promote greater rechargeability when cycled in Ag-Zn and Ni-Zn cells, even thwarting dendrite formation when cycled in symmetric Zn@ZnO-Zn cells at an applied current density twice that of the critical current density necessary to form dendrites [5]. All Zn-based chemistries can now be reformulated for next-generation rechargeable, Li-free batteries.
The information, data, or work presented herein was funded in part by the Office of Naval Research and by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR-0000391; the work has been Approved for Public Release, Distribution Unlimited.
[1] R.W. Hart, H.S White, B. Dunn, D.R. Rolison, Electrochem. Commun.5 (2003) 120-123.
[2] J.W. Long, B. Dunn, D.R. Rolison, H.S. White, Chem. Rev. 104 (2004) 4463-4492.
[3] D.R. Rolison, J.W. Long, J.C. Lytle, A.E. Fischer, C.P. Rhodes, T.M. McEvoy, M.E. Bourg, A.M. Lubers, Chem. Soc. Rev.38 (2009) 226-252.
[4] J.F. Parker, E.S. Nelson, M.D. Wattendorf, C.N. Chervin, J.W. Long, D.R. Rolison, ACS Appl. Mater. Interfaces6 (2014) 19471minus;19476.
[5] J.F. Parker, C.N. Chervin, E.S. Nelson, J.W. Long, D.R. Rolison, Energy Environ. Sci.7 (2014) 1117-1124.

New scientific paradigms in battery science and technology are needed to address energy issues associated with grid storage, electric vehicles, and portable electronics, where safety, energy density and power are all critical aspects of performance. Specifically, a critical challenge is the narrowing of the often considerable gap between theoretical energy content and realizable energy delivery of energy storage systems. While battery voltage and energy content can be estimated theoretically from electrode chemical compositions, the functional delivered energy from a battery also depends to a substantial extent on the physical properties of the electrode materials, where the dimensions of active material particles as well as the electrode design can have a large effect on the cycling performance of batteries.
In this presentation, factors impacting performance of a low cost nanosized iron based electroactive material for lithium ion batteries will be discussed. Material and electrode characterization over multiple length scales will be described to elucidate the roles of active material crystallite size, agglomerate size, and distribution when incorporated into a composite electrode. The characterization approaches and design principles described will be broadly applicable to other current and future energy storage systems.

One of the great potential technological improvements in energy storage is the ability to make multifunctional energy storage materials that can simultaneously store energy and function as a load bearing and structural material. We highlight the use of nanoporous materials, including nanoporous Si and anodized metals that are electrically and mechanically connected to bulk current collectors as an ideal structural energy storage architecture, and present electrochemical measurements while under simultaneous static and dynamic mechanical loads including tensile, shear, compression and vibratory loads for energy storage devices including carbonized porous Si supercapacitors. These devices can operate at commercial energy densities, and power densities, and can operate with minimal degradation under stresses greater than 1 MPa, and under vibratory accelerations greater than 80 g. In addition we show the importance of wet-dry performance on structural energy storage materials, and demonstrate the ability of devices with epoxy-ionic liquid electrolytes to function both mechanically and electrochemically in extreme environmental conditions such as immersion in water
References:
A.S. Westover et al., "A multifunctional load-bearing solid-state supercapacitor", Nano letters 14 (6), 3197-3202
A.S. Westver et al., "Multifunctional high strength and high energy epoxy composite structural supercapacitors with wet-dry operational stability", Submitted.

Many devices require both high energy and high power density, and lithium ion batteries and super-capacitors cannot separately always meet the requirements. In this work, we study the operating mechanism of a hybrid battery, which combines the best properties of batteries and supercapacitors. We analyze the lithium ion storage mechanism using XRD, Raman, TEM and electrochemical measurements. The model system studied combines a non-intercalating carbon black anode with a LiFePO₄ cathode. At 50% state of charge, XRD data for LiFePO₄ cathode material shows a mixture of LiFePO₄ and FePO₄, indicating battery reaction. On the other hand, the activated carbon remains structurally unchanged. We also discuss the impact of a range of activated carbon/ LiFePO₄ (AC/LFP) ratios. From cyclic voltammetry and charge/discharge results, the system exhibits battery-domain characteristics when the AC/ LFP ratio is below one, but showing more supercapacitor-domain traits when the ratio is higher. Besides, the systems have higher rate capacity at AC/LFP ratio around four as compared to one. This research is supported by NSF under Award Number 1318202.

Electrochemical energy storage is a growing focus for researchers and industry as new technology demands higher mobility and increased energy and power densities. To meet these energy storage needs, researchers have relied on an ever increasing collection of advanced materials. The long-term sustainability of both the materials and the processes to produce them have been called into question in recent years. This has resulted in a growing area of research in the area of sustainable energy materials. This work explores the ability to recycle industrial byproducts from both the petroleum and biomass industries into useful advanced materials for electrochemical energy storage. This includes lithium-sulfur batteries batteries with reversible capacities in excess of 600 mAh/g, corresponding to an energy density of ~1300 Wh/kg and with Coulombic efficiencies greater than 99%. Potassium-sulfur batteries are also explored as an alternative to lithium. The use of natural products such as sodium alginate for cathode binders and tannic acid as a separator pre-treatment are also explored.

Supercapacitors are promising energy storage devices due to their higher energy density than the dielectric capacitors and higher power density and long cycle life time compared with the conventional batteries. However, supercapacitor still suffers from a lower energy density than battery. One promising approach to increase the operation voltage and hence the energy density is to assemble asymmetric supercapacitors which combine the pseudocapacitve electrode which has high energy density, and the electric double layer capacitor electrode which provides high power density. The asymmetric configuration will take the advantage of different electrochemical windows in both electrodes to increase the cell operation voltage, resulting in an improved specific capacitance, energy and power densities.
In this abstract, an asymmetric supercapacitor exploiting nm-scale conformal coating of PEDOT on A-CNTs as the negative electrode and the ultrahigh density A-CNTs as the positive electrode was developed. Both electrodes were tailored separately to extend the cell operation potential to 4 V in 2 M 1-Butyl-3-methylimidazolium tetrafluoroborate (BMIBF4) /propylene carbonate (PC) electrolyte, leading high electrochemical performance.
The stable potential windows of -2.2 V to 1.3 V for the A-CNTs electrode and of -1 V to 1.8 V to the PEDOT/A-CNTs electrode. Thus, the operation window of asymmetric supercapacitor can be extended up to 4 V by tuning the mass ratio of the two electrodes. Since the charges stored in the two capacitor electrodes should be equal in magnitude with opposite signs (|q+|=|q-|), the mass ratio between the two electrodes can be determined. For a capacitor electrode, the stored charge q is q=C#8710;Vm. C is the specific gravimetric capacitance, #8710;V is the maximum potential range. The mass ratio between the two electrodes is determined by m+/m-=(C-#8710;V-)/(C+#8710;V+).
For the asymmetric capacitor developed here, the specific capacitances of the positive and negative electrodes are 205 F/g and 121 F/g, respectively, at a constant discharge current of 1 A/g. The optimal mass ratio of the two electrodes can be deduced to be 0.72.
The asymmetric cells exhibit both high volumetric and gravimetric maximum power density and energy density, which are 130.6 kW L^-1 (269.4 kW kg^-1) and 82.8 Wh L^-1 (170.7 Wh kg^-1), respectively.

Application demands in portable electronics, electrical transportation and grid scale storage call for next generation of batteries with high energy, long cycle life, good safety and low cost. Here I will present my group research on how we reinvented batteries from materials design to cell architecture. The following research topics will be discussed: 1) High capacity anodes (Si, Li and P) through nanoscale materials design. Multiple generations of materials design and invention of novel concepts include nanowires, core-shells, hollow particles, yolk-shells, double-walled hollow tubes, pomegranates, conducting hydrogel and self-healing. 2) Novel safe and smart battery separators with dendrite detection capability and solid nanostructure-polymer composite electrolyte with enhanced ionic conductivity.

Exploring a new chemistry in metal-gas systems plays a key role in creating new possibilities in the development of an ultra-high-energy-density battery, as it enables electrochemical energy storage without the use of a heavy transition metal redox host. Recent reports on various metal-gas rechargeable batteries, such as Na-O₂, K-O₂, Al-O₂, and Li-CO₂ systems, reveal their potential applicability as high-energy-storage media with unique electrochemical properties depending on the combination of metal and gas^4-9. In this communication, we shed new light on conventional Li-SO₂ batteries, which have been widely used for military devices because of their wide operating temperature range, high energy density, and long shelf life. Although Li-SO₂ batteries have been used as primary batteries to date, the feasibility of a rechargeable Li-SO₂ battery is demonstrated here based on the reversible formation and decomposition of the solid product, Li₂S₂O₄. This novel rechargeable Li-SO₂ battery is capable of delivering a discharge capacity of approximately 5,400 mAh g^-1 at 3.1 V, which is slightly higher than that of a Li-O₂ battery. Moreover, the charge polarization is markedly lower than that of a Li-O₂ cell even without a catalyst. Consequently, the observed energy efficiency of the Li-SO₂ system is significantly better than that of the Li-O₂ system. With the aid of a redox mediator, the system can exhibit a polarization of lower than 0.3 V, which is one of the highest energy efficiencies achieved for Li-gas battery systems to date.
Reference
1. Peng, Z., Freunberger, S. A., Chen, Y. & Bruce, P. G. A Reversible and Higher-Rate Li-O₂ Battery. Science 337, 563-566 (2012).
2. Hartmann, P., et al. A rechargeable room-temperature sodium superoxide (NaO₂) battery. Nat Mater 12, 228-232 (2013).
3. Ren, X. & Wu, Y. A Low-Overpotential Potassium-Oxygen Battery Based on Potassium Superoxide. J Am Chem Soc 135, 2923-2926 (2013).
4. Mori, R. A novel aluminium-air secondary battery with long-term stability. RSC Adv 4, 1982-1987 (2014).
5. Ren, X. & Wu, Y. A Low-Overpotential Potassium-Oxygen Battery Based on Potassium Superoxide. J Am Chem Soc 135, 2923-2926 (2013).
6. Gowda, S. R., Brunet, A., Wallraff, G. M. & McCloskey, B. D. Implications of CO₂ Contamination in Rechargeable Nonaqueous Li-O₂ Batteries. J Phys Chem Lett 4, 276-279 (2013).
7. Takechi, K., Shiga, T. & Asaoka, T. A Li-O₂/CO₂ battery. Chem Commun 47, 3463-3465 (2011).
8. Shiga, T., Hase, Y., Kato, Y., Inoue, M. & Takechi, K. A rechargeable non-aqueous Mg-O₂ battery. Chem Commun 49, 9152-9154 (2013).
9. Liu, Y., Wang, R., Lyu, Y., Li, H. & Chen, L. Rechargeable Li/CO₂-O₂ (2 : 1) battery and Li/CO₂ battery. Energy Environ Sci 7, 677-681 (2014).

One of the most promising avenues for future high energy Li-ion batteries come from the family of Li-rich layered composite/solid solution cathodes. However, while exhibiting excellent initial capacity, these materials also suffer from voltage fade and poor rate capability, particularly in the Mn-rich, Li excess regime. The voltage fade mechanism has been established as due to inherent structural and chemical transformation as the material is charged, however, the delithiation mechanism involving coherent Li migration from two layers is not yet clearly understood. In this work, we investigated delithiation mechanisms of the end member of Li-rich composite materials (Li2MnO3) by first principle Density Functional Theory and kinetic Monte Carlo. Our calculations show that the diffusion coefficient of Li2MnO3 in the high lithium content region is comparable with other commercialized cathodes such as LiCoO2 and LiTiS2. We confirmed that the Li-extractions are found in both the transition metal and Li-layer, and those Li-extractions can be accelerated by di and tri-vacancy clusters. A generic effect of the vacancy cluster is to stabilize the saddle point tetrahedral sites. Hence, the poor rate behavior of this class of Li cathode materials is likely not due to intrinsic bulk migration, but instead to other effects, such as surface-related reconstruction and/or particle-particle contact.

3,7shy;Bis(trifluoromethyl)shy;Nshy;ethylphenothiazine (BCF3EPT) is one of several derivatives of phenothiazine prepared in our laboratory for evaluation as redox shuttles for overcharge protection in lithiumshy;ion batteries. An alkyl group at the N position and electronshy;withdrawing trifluoromethyl groups at the 3 and 7 positions have led to this robust derivative with high solubility in organic solvents.^1,2 With a reversible oxidation potential at 3.8 V vs Li^+/0 and no observable reduction, this compound is useful as a redox shuttle for overcharge protection in some lithium-ion battery systems and as a catholyte in non-aqueous redox flow batteries. Though many electron-donating organic compounds have been reported to have high solubilities and others have higher oxidation potentials, the combination of stability and solubility in this derivative have led it to yield the most extensive overcharge protection to date in side-by-side tests with well-performing dialkoxybenzene derivatives, including protection at charging rates as high as 1C. We have also reported stationary mimics of non-aqueous flow batteries containing this compound that survive to 50 cycles before significant capacity loss³ and have more recently tested half cells that survive for at least 300 cycles with high cycling efficiencies. This presentation will include the optimized synthesis of this compound, with >90% yield per reaction and three steps total, as well as performance in various energy storage applications.
References:
1. “Overcharge Performance of 3,7-Disubstituted N-Ethylphenothiazine Derivatives in Lithium-Ion Batteries.” Ergun, S.; Elliott, C.F.; Kaur, A.P.; Parkin, S.R.; Odom, S.A. Chemical Communications, 2014, 50, 5339-5341.
2. “3,7-Bis(trifluoromethyl)-N-Ethylphenothiazine: A Redox Shuttle with Extended Overcharge Protection.” Kaur, A.P.; Ergun, S.; Elliott, C. F.; Odom, S.A. Journal of Materials Chemistry A, 2014, 2, 18190-18193.
3. “A Highly Soluble Organic Catholyte for Non-Aqueous Redox Flow Batteries.” Kaur, A.P.; Holubowitch, N.E.; Ergun, S.; Elliott, C.F.; Odom, S.A. Energy Technology, 2015, 3, 476-480.

Rechargeable metal batteries, such as Li and Na metal batteries are considered the “holy grail” of energy storage systems. However, dendritic metal growth and limited Coulombic efficiency (CE) during metal deposition/stripping have prevented their applications in rechargeable batteries.¹ During the last a few years, we have developed several approaches to suppress metal dendrite growth and enhance the Coulombic efficiency of metal deposition/stripping processes.^2-6 A new strategy based on Self-Healing Electrostatic Shield (SHES) mechanism has been developed to suppress Li dendrite growth. We also demonstrate that a controlled trace-amount of H₂O (25-50 ppm) can be an effective electrolyte additive for achieving dendrite-free Li metal deposition in LiPF₆-based electrolytes. Furthermore, we have developed a highly concentrated electrolytes composed of the lithium bis(fluorosulfonyl)imide (LiFSI) salt and 1,2-dimethoxyethane (DME) solvent which enables high rate cycling of Li metal anode at high CE (up to 99.1 %) without dendrite growth.⁶ It is demonstrated that a Li|Li cell can be cycled at high rates (10 mA cm^-2) for more than 6,000 cycles with no increase in the cell impedance and no dendritic Li growth. A Li|Cu cell can be cycled at 4 mA cm^-2 for more than 1,000 cycles with an average CE of 98.4%. Novel electrode was also developed which enables cycling of Na metal anode with an excellent CE. Further development of these electrolytes may lead to practical applications of metal anode in rechargeable batteries.
References
D. Aurbach, E. Zinigrad, Y. Cohen, and H. Teller, Solid state ionics, 148, 405-416 (2002).
W. Xu, J. Wang, F. Ding, X. Chen, E. Nasybulin, Y. Zhang and J.-G. Zhang, Energy Environ. Sci., 7, 513-537 (2014).
F. Ding, W. Xu, G. L. Graff, J. Zhang, M. L. Sushko, X. Chen, Y. Shao, M. H. Engelhard, Z. Nie, J. Xiao, X. Liu, P. V. Sushko, J. Liu, J.-G. Zhang, J. Am. Chem. Soc., 2013, 135 (11), pp 4450-4456. J. Am. Chem. Soc., 135, 4450-4456 (2013).
Yaohui Zhang, Jiangfeng Qian,Wu Xu, Selena M. Russell, Xilin Chen, Eduard Nasybulin,Priyanka Bhattacharya, Mark H. Engelhard, Donghai Mei, Ruiguo Cao, Fei Ding, Arthur V. Cresce, Kang Xu, and Ji-Guang Zhang, Nano Lett., 2014, 14 (12), pp 6889-6896.
Jiangfeng Qian, Wu Xu, Priyanka Bhattacharya, Mark Engelhard, Wesley A. Henderson, Yaohui Zhang, Ji-Guang Zhang, Nano Energy, Nano Energy(2015) 15, 135-144.
Jiangfeng Qian, Wesley A. Henderson, Wu Xu, Priyanka Bhattacharya, Mark Engelhard, Oleg Borodin,Ji-Guang Zhang, Nature Communications, | 6:6362 | DOI: 10.1038/ncomms7362.

Sodium ion batteries stand out as an alternative to the lithium based technology due to wide global abundance of sodium and potential cost advantage. [1] However, the larger size of Na⁺ compared to Li⁺ makes it more difficult to find host materials that can reversibly accommodate the ions in the structure. In that sense, polymers can comply with interchain volume occupation. Besides, organic electrode materials are interesting due to the cost saving in terms of lower price of the precursors and cheaper synthetic methodology. Polymers are typically included in electrode formulations as binder and its role is crucial to guarantee the proper interparticle contact and adhesion to the current collector during cycling. Namely, poly(vinylidene) fluoride (PVdF) has been widely used as binding agent but it decomposes below 1V vs. Na⁺/Na from dehydrofluorination. [2] Although other polymers such as carboximethylcellulose, polyacrylic acid or sodium alginate have shown better cycle life that PVdF, their use implies deadweight effect on the electrode with no contribution to the capacity, and requires the use of an extra additive such as carbon black to enhance conductivity. [3]
It has been reported in the literature that Schiff-base entities attached to an aromatic ring by its carbon atom (-N=CH-Ph-HC=N-) show redox activity at low potentials vs. Na⁺/Na. [4] Herein we report on the synthesis of a family of poly-Schiff base/oligoether terpolymers that exhibit a double role as they show electrochemical activity and good binding properties. This is due to the incorporation of poly(ethylene oxide) (PEO) linkers within the polymer chain and side groups providing the polymer with flexibility and ionic conductivity. Post-mortem micrographs of the electrodes reveal that the material shows no detachment, proof of the good self-binding properties. In a classical configuration, when cast with PVdF binder in the presence of C65, it shows a reversible capacity of 200 mAh/g for 50 cycles proving the good electrochemical activity of this double-roled material. Alternatively, it can be successfully deployed as a binder of other negative electrode materials which represents a proof of concept in the field of redox active binders mediating redox reaction.
References
[1] V. Palomares, P. Serras, I. Villaluenga, K. B. Hueso, J. Carretero-González and T. Rojo. Energy Environ. Sci.,2012, 5884-5901.
[2] M.A. Muñoz-Márquez, M. Zarrabeitia, E. Castillo-Martínez, A. Eguía-Barrio, T. Rojo, M. Casas-Cabanas. ACS Appl. Mater. Interfaces., 2015, 7 (14), 7801-7808.
[3] S. Komaba, Y. Matsuura, T. Ishikawa, N. Yabuuchi, W. Murata, S. Kuze. Electrochem. Comm.2012, 21, 65-68.
[4] E. Castillo-Martínez, J. Carretero-González, M. Armand. Angewandte Chemie Int. Ed.,2014, 53, 5341-5345.

Single solvent is difficult to meet the needs of lithium air batteries, but the complementary nature of the electrolyte can be obtained by mix two or more solvents. N,N-dimethylacetamide (DMA) is stable in the air, it won't break down even after long time contact with oxygen. Additionally, when lithium nitrate(LiNO3) has been used as an accretion in DMA, a stable solid-electrolyte interphase (SEI) can be formed under oxygen which offsets the deficiency of dimethyl sulfoxide (DMSO). Here LiNO3 as the lithium salt using DMA and DMSO based electrolyte has been investigated for rechargeable Li-O2 batteries. Discoveries show that rate capability can be as high as 380mA g-1 and charge over-potential is 0.44V lower than lithium bis (trifluoromethanesulfonyl)imide(LiTFSI)/tetra ethylene glycoldimethylether (TEGDME).

The solvation of Li⁺ and anions in lithium ion battery electrolytes is a key factor controlling the passivation of electrodes, especially graphite anodes. The preferential solvation of Li⁺ by cyclic carbonates in specific situations has now been well described, and this behavior causes the formation of a solid electrolyte interphase at the graphite anode dominated by the products of cyclic carbonate reduction. With increasing interest in low-cost large-format energy storage utilizing sodium ion batteries, it is necessary to examine the fundamental solvation behavior of Na⁺ in order to begin addressing the formation and chemistry of solid electrolyte interphase formation on sodium ion electrodes. In this work, we will examine the solvation of Na⁺ in several organic solvents, including those from the carbonate family. Because of differences in size, hardness, and chemical activity, Na⁺ will likely exhibit differences from Li⁺ in terms of solvent preferences and solvent-Na⁺ interaction. While previous work has demonstrated sodium ion electrolytes will passivate electrodes such as MoS₂, so far little is known about the passivation of electrodes by sodium ion electrolytes and how or if this passivation is linked to Na⁺ solvation. Using similar tools to those used to study Li⁺ solvation, including electrospray ionization mass spectrometry and nuclear magnetic resonance techniques, we will explore the solvation environment of Na⁺ and how that may contribute to the passivation of relevant sodium electrodes.

There has been an increasing demand for high capacity electrical storage devices for use of hybrid electrical vehicle (HEV) and plug-in hybrid electrical vehicle (PHEV). Among various lithium battery systems, Li-O₂ battery is one of the most promising candidates for HEV and PHEV due to its extremely high capacity (11.140kWh/kg), which can be achieved by allowing Li to react with O₂ directly from the infinite air.[1] Its superior charge storage ability is about 10 times larger than that of conventional Li rechargeable batteries. However, the limitation of poor cycle life and power capability remains as a critical drawback of Li-O₂ battery.
Here, we design a hierarchical carbon electrodes with highly aligned CNT fibrils, and demonstrate that these electrodes with aligned pores can significantly enhance the cyclability and rate capability of Li-O₂ battery.[2] The hierarchically porous air electrode was designed by cross-weaving aligned CNT sheets, which allows the facile accessibility of oxygen to the inner electrode and leads to a uniform deposition of discharge products on the individual CNTs without clogging the electrode even at a deep discharge state. Additionally, we combined hierarchically porous air electrode with effective catalyst decoration. The decoration of solid catalyst on CNT fibrils can further enhance the rechargeability of Liminus;O₂ battery over 100 cycles with full discharge and charge.[3] Furthermore, we demonstrate a novel Li-O₂ battery with high reversibility and good energy efficiency using a new soluble catalyst combined with a hierarchical nanoporous air-electrode.[4] Through the porous three-dimensional network of the air-electrode, not only lithium ions and oxygen but also soluble catalysts can be rapidly transported, enabling ultra-efficient electrode reactions and significantly enhanced catalytic activity. The novel Li-O₂ battery, combining an ideal air-electrode and a soluble catalyst, can deliver a high reversible capacity (1000 mAh g^-1) up to 900 cycles with markedly reduced polarization (~0.25 V).
[1] P. G. Bruce, S. A. Freunberger, L. J. Hardwick and J.-M. Tarascon, Nat. Mater., 2012, 11, 19.
[2] H.-D. Lim, K.-Y. Park, H. Song, E. Y. Jang, H. Gwon, J. Kim, Y. H. Kim, M. D. Lima, R. O. Robles, X. Leproacute;, R. H. Baughman and K. Kang, Adv. Mater., 2013, 25, 1348.
[3] H.-D. Lim, H. Song, H. Gwon, K.-Y. Park, J. Kim, Y. Bae, H. Kim, S.-K. Jung, T. Kim, Y. H. Kim, X. Lepro, R. Ovalle-Robles, R. H. Baughman and K. Kang, Energy Environ. Sci., 2013, 6, 3570.
[4] H.-D. Lim, H. Song, J. Kim, H. Gwon, Y. Bae, K.-Y. Park, J. Hong, H. Kim, T. Kim, Y. H. Kim, X. Leproacute;, R. Ovalle-Robles, R. H. Baughman and K. Kang, Angew. Chem., Int. Ed., 2014, 53, 3926.

Lithium-air and lithium-sulfur battery chemistries are particularly attractive for large scale energy storage due to the exceptionally low cost of raw materials used in the positive electrode and their high gravimetric capacities. However, both Li-Air and Li-S batteries are based on complex solution chemistries that lead to the generation of soluble species that ultimately precipitate and must be stored in the positive electrode matrix without degrading battery performance, and this process must be reversed when the cells are charged. In Li-S cells there is also the well known phenomenon of the polysulfide shuttle that leads to high rates of self-discharge. In the case of true “Li-Air” cells, there is the added problem of moisture attack on the lithium metal electrode (dry oxygen can be used to solve the moisture problem but this defeats the energy density advantages of Li-Air chemistry). Both the polysulfide shuttle (Li-S) and moisture problem (Li-Air) are solved by introducing a solid electrolyte membrane into the cell construction in the form of a protected lithium electrode or PLE. PolyPlus uses water-stable solid electrolytes that further allow the use of unusual solvent systems including aqueous electrolytes. In this presentation we will discuss the state-of-the-art in both Li-Air and Li-S battery technology as well as the state-of-the-art in protected electrode architectures.

As the essential component in any energy storage device, electrolyte determines a number of key performances of the device, including temperature range for service, rate of electrochemical reaction, safety under both normal and abusive operations, cycle/calendar life as well as the maximum voltage allowed. Among these, the electrochemical stability window is perhaps the most intriguing property, because in almost all electrochemical devices, the electrodes operate at potentials far beyond what thermodynamics allowed. This group at ARL has been trying to understand this basic phenomenon and exploring various means to affect the surface chemistry at electrode/electrolyte junctions, so that this stability window could be expanded to enable more powerful battery chemistries. This talk will summarize these recent efforts.

Grid-level energy storage to address the intermittency challenge from renewable energy sources such as solar and wind depends on the development of a cost-effective and safe stationary storage system. The development of a redox flow battery based on water-soluble organic molecules such as anthraquinone-2,6-disulfonate has shown a promising pathway toward this end.[1]-[3] Remaining challenges, such as membrane crossover of undesired species and cost of containment for toxic and corrosive electrolytes, are the subject of active research. Here we report a novel quinone-based aqueous redox flow battery employing commercially available, stable and non-toxic electrolyte materials. The open circuit voltage is over 1.2 V, the peak galvanic power density exceeds 0.35 W/cm², the membrane crossover rate is orders of magnitude lower than with inorganic redox couples, and the current efficiency is beyond 99.2% per cycle.
[1] B. Huskinson, M.P. Marshak, C. Suh, S. Er, M.R. Gerhardt, C.J. Galvin, X. Chen, A. Aspuru-Guzik, R.G. Gordon and M.J. Aziz, “A metal-free organic-inorganic aqueous flow battery”, Nature505, 195 (2014), http://dx.doi.org/10.1038/nature12909
[2] B. Huskinson, M.P. Marshak, M.R. Gerhardt and M.J. Aziz, “Cycling of a quinone-bromide flow battery for large-scale electrochemical energy storage”, ECS Trans.61, 27 (2014)
[3] B. Yang, L. Hoober-Burkhardt, F. Wang, G. S. Prakash and S. R. Narayanan, “An Inexpensive Aqueous Flow Battery for Large-Scale Electrical Energy Storage Based on Water-Soluble Organic Redox Couples”, Journal of The Electrochemical Society161, A1371-A1380 (2014).

Iron anodes in aqueous alkaline media are employed in the highly robust Edison battery with possible lifetimes measured in decades and are also being pursued for use in metal-air systems. Recent work has focused largely on highly pure carbonyl iron microparticles as starting materials and/or use of surfactant or sulfide additives to combine long-term cycling stability with improved capacity utilization and efficiency. Here, we focus on common iron oxides, mainly hematite and magnetite as the materials used for the preparation of the alkaline iron anode. We track phase evolution in situ using synchrotron x-ray diffraction to confirm an initial irreversible transformation followed by a sequence of reversible phase transformations in electrodes prepared with iron oxide particles. Even when reduction capacities reach values suggesting formation of metallic iron, no corresponding diffraction peaks are detected. Possible implications of this finding will be discussed in light of SEM studies of morphology. Depending on the electrolyte salt used (LiOH or KOH), some intercalation (of Li+ or H+) into the reoxidation products is observed, in line with implications from earlier observations.
We also find that capacity utilization and efficiencies approaching that of the state-of-the-art metallic iron anodes can be achieved, at least in the first 50-100 cycles, under specific electrode formulations and cycling protocols. While the iron oxide based anodes might not be able to match iron-based anodes in terms of volumetric energy density, they offer the possibility of using lower cost starting forms of active materials, e.g. for stationary storage. Other possible advantages of the iron oxide starting materials is discussed in terms of stability and electrode formation processes.

Redox flow batteries (RFBs), as one of the most promising electrical energy storage systems, provide an alternative solution to the problems of balancing power generation and consumption. RFBs are designed to convert and store electrical energy into chemical energy and release it in a controlled fashion when required. Of them, all vanadium system (VRBs), utilizing vanadium-containing chemicals as positive V(IV)/V(V) and negative V(II)/V(III) electrolytes, is one of the redox systems which have reached commercial fruition, due to its large voltage window and energy densities.^[1] Especially, recently invented mix-acid based all vanadium system by Liyu Li and co-workers^[2] at PNNL largely improved the solubility of vanadium ions in electrolytes and thus charging/discharging energy densities, which greatly enhances the market competition of all vanadium RFBs in energy storage technologies. It is well known that high charge/discharge rate (charge/discharge current density) is prone to generate high power density, but the energy efficiency (EE) would be significantly declined. In order to increase EE especially at higher current density, much attention has been paid on the improvement of electrodes. Commonly, carbon-based materials are used as electrodes in VRBs because they are readily available, highly stable, corrosion resistant, economical and conductive. However, they were proved to show poor kinetic reversibility. Although noble metal catalysts such as Pt, Au, Ir, and Pd^[3] were coated or dispersed onto the carbon surfaces so as to improve the electrochemical activity of active species, the high cost and complex coating process still restrict their commercial application. Recently, B. Li et al. at PNNL developed low-cost bismuth nanoparticles ^[4] and Nb₂O₅-based nanorods^[5] deposited on the surface of graphite felts, which were found to exhibit powerful catalytic effect.
Here, we decorated the surfaces of graphite felts with some oxygen-containing functional groups, such as C-OH, O=C and HO-C=O. And the mole ratios and amounts of these functional groups were effectively adjusted on the graphite surface by a particular method. The catalytic effects of amounts and mole ratio of different kinds of functional groups on VRB electrode performances were investigated in detail.
[1] Wang, W.; Luo, Q.; Li, B.; Wei, X.; Li, L.; Yang, Z. Advanced Functional Materials 2012, DOI:10.1002/adfm.201200694.
[2] Li, L.; Kim, S.; Wang, W.; Vijayakumar, M.; Nie, Z.; Chen, B.; Zhang, J.; Xia, G.; Hu, J.; Graff, G.; Liu, J.; Yang, Z. Advanced Energy Materials 2011, 1, 394.
[3] Sun, B; Skyllas-Kazacos. Electrochimica Acta 1991, 35, 513
[4] Li, B, et al. Nano letters 13.3 (2013): 1330-1335.
[5] Li, B et al. Nano letters 14.1 (2013): 158-165.

Thin films of polyaniline are conductive and can be used in a variety of applications including supercapacitors, actuators and photovoltaic devices. However, the electrodeposition of polyaniline from the aniline precursor requires a highly proton rich (acidic) electrolyte, and the rate of film growth and thickness can be dependent on the proton activity in the solution. Here we report a novel alternative approach where we pre-protonate the aniline to form anilinium nitrate [1], which can be considered an ionic liquid. Due to the pre-protonation the anilinium nitrate could be dissolved in electrolyte media for deposition without the need for a highly acidic medium. Thick yet porous deposition was achieved when the anilinium nitrate was dissolved in the protic ionic liquid of ethylammonium nitrate (EAN). For example, a thick polyaniline film of 1.9 Ccm^-2 was obtained on a 1.6 mm diameter Pt working electrode after 30 cyclic voltammatric depositions of polyaniline between -0.65 V to +0.60 V vs. Ag/Ag⁺ from a 380 mM solution of anilinium nitrate in EAN. Consequently the films are ideal for energy storage applications and should have high energy (due to thick deposit) and high power (due to porosity). The key benefits of the pre-protonation step was that the electrodeposition no longer required a highly acidic medium, the anilinium nitrate could be dissolved in the solution at higher concentrations than aniline typically is, and due to high anilinium nitrate concentrations there is minimal effect on film growth due to depletion of the precursors.
The formation of an aniline-acid combination which is liquid at room temperature would enable the anilinium salt to be used as solvent, electrolyte and monomer. We have used high throughput techniques to screen nine aniline derivatives with six acids, and identified 5 successful candidates [2]. Of these, n-ethylanine trifluoroacetic acid was selected for further studies, and was successfully electropolymerised into thin conductive films. Overall, this novel approach of using a pre-protonated aniline derivative as the precursor enables a safer (less acidic) medium and can lead to high quality thick and porous conductive polymer films.
[1] G. A. Snook, T. L. Greaves and A. S. Best., J. Mater. Chem., 2011, 21, 7622
[2] M. E. Abdelhamid, T. Murdoch, T. L. Greaves, A.P. O&’Mullane and G. A. Snook, PCCP, 2015, DOI: 10.1039/c5cp02294k

The automotive segment of the global lithium-ion battery market is slated for exceedingly high growth in the near future, stoking a demand for next-generation electrode materials capable of delivering the 400 Wh/kg benchmark at low-costs. While most of the recent research efforts to enable such materials focus on complex material modifications and nano-architectured electrode design, developing alternative electrolyte chemistries presents another avenue towards creating the next generation Li-ion battery. Previous work at the University of Colorado demonstrated the viability of this approach. By pairing a simple, scalable, yet robust Si electrode architecture with an imide-based room temperature ionic liquid (RTIL) electrolyte, this work enabled a Si/L333 full-cell capable of long-term cycling (>1000 cycles) at a charge-discharge rate of 1C.¹ Recently an initial feasibility study has revealed the impressive compatibility of the same imide-based RTIL electrolyte with lithium-manganese-rich (LMR) layered oxides. In this talk, these results will be presented in more detail.
1. Molina Piper, D. et al. Stable silicon-ionic liquid interface for next-generation lithium-ion batteries. Nat. Commun. 6, 6230 (2015).

Li-S battery has attracted many interests due to its high energy, however, the dissolution loss of sulfur, shuttle effect and thus-resulted capacity decay greatly hinders its application. Using ion-liquid was found to be an effective way to enhance the cycling life of Li-S cell, however, the commercially available ion-liquid of PYR₁₀₄TFSI( N-Butyl, methyl pyrrolidinium bis(trifluoromethylsulfonyl)imide) has a high viscosity and thus has to be used together with other common ether solvent. In this paper, a new ion-liquid PYR₁₀₂TFSI and PYR₁₀₃TFSI was prepared and used in Li-S battery, the electrolyte with different combination and different ratio of the ion liquid was tested. The results show that using ion liquid-contained electrolyte can significantly improve the charge/discharge efficiency as well as the cycling stability of the Li-S cell. For example, the 10% capacity loss was observed on the Li-S cell with ion-liquid electrolyte while more than 25% capacity decay was observed on the cell with common electrolyte. In addition, the enhanced cycling stability seemed to be more significant on the “thick” electrode. Generally, using ion-liquid electrolyte can improve the electrochemical performance of the Li-S cell and the reason for the improvement very possibly is related to the alleviated dissolution loss.

In order to obtain a fundamental understanding of multivalent ion insertion in battery electrodes, it is important to gain insight into the location of ions inside the electrode material and the possible role of ion solvation in assisting ion insertion. Copper hexacyanoferrate (CuHCFe) is a promising electrode material for grid-scale energy storage and demonstrates remarkable reversible electrochemistry for a range of monovalent and multivalent ions in aqueous electrolytes [Wang et al., Advanced Energy Materials, 1401869 (2015)]. It is therefore an excellent candidate for systematic study of the occupancy, hydration and disorder of insertion ions in these electrodes following electrochemical activity. We use extended x-ray absorption fine structure (EXAFS) data collected at the absorption edge of three insertion ions (Rb⁺, Pb²⁺ and Y³⁺) to understand the hydration shell around the ions. The fourier-transformed EXAFS data strongly suggests that the inserted ions invariably possess some degree of hydration. We also collected total x-ray scattering data to obtain the specific location of ions inside the CuHCFe crystal structure. Analysis of the total scattering data yields pair distribution functions (PDF) that provide model-independent ion-ion and ion-framework distances in the pristine (oxidized) and fully reduced CuHCFe electrodes. Structural information obtained from these x-ray scattering and spectroscopy measurements provide new details of multivalent ion insertion and allow us to better understand structure-property relationships in batteries with aqueous electrolytes.

Grid scale energy storage urgently calls for high-efficient, large-scale and low-cost energy storage devices. For these demands, liquid metal batteries (LMBs) have the potential to accomplish low cost, long cycle life and high energy efficiency, enabled by low cost electrode materials, liquid electrodes with no structural degradation, fast electrode kinetics at the electrode/electrolyte interface and high ionic conductivity of molten salt electrolyte.Herein, detailed investigations were carried out of the positive Sb-Pb electrode in LiF-LiCl-LiBr molten salt using a three-electrode setup. Cyclic voltammograms (CVs) of the Sb, Pb and Sb-Pb showed that blending Pb into Sb slightly reduced the electronegativity of Sb, and Li was preferentially alloyed with Sb at 0.92 V and subsequently alloyed with Pb. At a discharge rate of 275 mA cm^-2, Li only alloyed with Sb when the potential was above 0.6 V (vs Li). A smooth and solid intermetallic layer containing Li₂Sb and Li₃Sb formed on the top of liquid Sb-Pb electrode during the discharge process which was known as the alloying. As the intermetallic grew, Sb was gradually separated from the Pb and alloyed with Li.

The inorganic/organic duality and the dynamic interactions between the electrochemical generated superoxide radical (O₂^bull;minus;) and structurally different ionic liquids (ILs) was characterized by electrochemical quartz crystal microbalance (EQCM) which is the one of the most important reactions for battery development as well as real life applications of gas sensors. Particularly, the electrochemical behavior of O₂/O₂^bull;minus; couple and the ion-pairing formation between the cation of an IL and O₂^bull;minus;were investigated in three structurally different ILs. The O₂^bull;minus; tends to form ion-pair complex with the cation of an IL, subsequently abstracting a proton to form different products depending upon the cation structure of the IL used. The reversibility of O₂/O₂^bull;minus; electrode reaction depends on the following chemical reactions between O₂^bull;minus; and the IL which is more pronounced at slow scan rates. It was found that O₂^bull;minus; is significantly more stable in the IL with [BMPY] cation than those of imidazoliumsalts. The stability of the ILs toward the O₂^bull;minus;attack follows the order of [BMPY][NTf₂]>[BdMIM][NTf₂]>[BMIM][NTf₂]. Furthermore, the formation of [cation]hellip;O₂^bull;minus; ion-pair complex is shown to lower the local viscosity of the ILnear the electrode, reflected in the QCM oscillating frequency change. The QCM response is also affected by the diffusion of the cation. This study demonstrates that EQCM is an effective tool to characterize the redox reaction at an IL/electrode interface which has potential applications both for sensors and energy harvesting.

Si is an attractive negative electrode material for lithium ion batteries due to its high specific capacity (~3600 mAh/g). However, the huge volume swelling and shrinking during cycling leads to several coupled mechanical and chemical degradation at the material/electrode/cell level, including fracture of Si particles, unstable solid electrolyte interphase (SEI), and low Coulombic efficiency. In this talk, we will discuss how to improve the cycle efficiency from those aspects, starting with the fundamental understanding of the relationship between the structure and properties of SEI to pinpoint the SEI failure mechanisms. Then we will discuss how to develop artificial SEI, combining the design of Si nanostructure to enable the high cycle efficiency. At last, we will discuss how the nanostructure design at material level can impact the electrochemical-mechanical behaviors at electrode and cell level.

There is an ever-increasing demand for the rechargeable lithium-ion batteries (LIBs) in the upcoming era of portable electronics, electric transportation and smart grids, owing to their high energy and mature fabrication technologies. The further development and large-scale application of LIBs, however, has brought growing concern from both academia and industry in recent years regarding the increasing cost and an uneven geological distribution of lithium source. By comparison, sodium (Na) is environmentally benign and is the sixth abundant element in the Earth#1523;s crust, while the sodium salts used to prepare battery materials are plentiful. Furthermore, the standard electrode potential of Na/Na⁺ at 2.71 V and of Li/Li⁺ at 3.02 V are very close to each other, and the non-aqueous electrolytes containing sodium salts usually show similar electrochemical windows, comparable ionic conductivities and stabilities to lithium-ion counterparts. In this context, sodium-ion based rechargeable batteries hold great promise as low-cost alternative power sources to LIBs for future energy storage technologies.
Currently, the key factor is to develop suitable electrode materials with sufficient interstitial space for sodium ions storage and transportation. Recent research shows that many transition metal oxides, fluorophosphates, fluorosulphate, and ferricyanide can serve as electrode materials with a certain capacity. However, these non-carbon based inorganic materials can hardly be dominant due to the environmental benignity and cost considerations. In this context, developing novel carbon-based anode materials with high reversible capacity and rate capability is still challenging and urgently needed. Herein, we report, for the first time, the graphene sheets covalently bonded with sulfur atoms as Na-ion battery anode material with a large reversible capacity of 291 mA h g^minus;1 and an outstanding rate capability with 127 and 83 mA h g^minus;1 at 2.0 and 5.0 A g^minus;1 (charging/discharging in 3.8 and 1 min, respectively), and a long cycling stability as well. Both experiment and density functional theory calculation proves that the superior performance is mainly attributed to the unique nanoporous structure stemmed from the chemically S doping. This material holds great promise in future application of low cost, high-performance Na-ion batteries.

Many high-energy-density lithium ion battery electrode materials have been studied to meet the requirements for lighter weight and longer battery life. For example, silicon is able to deliver 3600 mAh/g by forming Li₁₄Si₄, which is higher than the specific capacity of other known negative-electrode materials. However, Li-Si has poor cycle life and low cycling efficiency due to coupled mechanical and chemical degradation, which leads to quick capacity fade upon cycling. One of the most important degradation mechanisms is the failure of solid electrolyte interphase (SEI). When SEI fails, it will cause irreversible lithium consumption in the lithium ion battery system.
The SEI is a passivation layer formed between the electrolyte (liquid) and electrode surface (solid) to enable the long-term cyclability. Previous studies have identified two critical inorganic components of SEI: lithium fluoride (LiF) and lithium carbonate (Li₂COshy;₃). Our work presented here demonstrate the function of each component, and identity the coupling effects of LiF and Li₂CO₃. We envision that this work can provide a general guideline in the design of artificial SEIs to improve the current efficiency and increase the life of lithium ion batteries.

One-dimensional nanomaterials can offer large surface area, facile strain relaxation upon cycling and efficient electron transport pathway to achieve high electrochemical performance. Hence, nanowires have attracted increasing interest in energy related fields.
We designed the single nanowire electrochemical device for in situ probing the direct relationship between electrical transport, structure, and electrochemical properties of the single nanowire electrode to understand intrinsic reason of capacity fading. The results show that during the electrochemical reaction, conductivity of the nanowire electrode decreased, which limits the cycle life of the devices. Then, the prelithiation and Langmuir-Blodgett technique have been used to improve cycling properties of nanowire electrode. Recently, we have fabricated hierarchical MnMoO₄/CoMoO₄ heterostructured nanowires by combining "oriented attachment" and "self-assembly". The asymmetric supercapacitors based on the hierarchical heterostructured nanowires show a high specific capacitance and good reversibility with a cycling efficiency of 98% after 1,000 cycles. Furthermore, we fabricated Li-air battery based on hierarchical mesoporous LSCO nanowires and nonaqueous electrolytes, which exhibits ultrahigh capacity over 11000 mAh g^-1. We also designed the hierarchical zigzag Na_1.25V₃O₈ nanowires with topotactically encoded superior performance for sodium-ion battery cathodes. Through our study, it will solve the challenge of property degradation and it may provide extend effect and helpful methods in directions, in energy storage and in open new applications.

Over the past years, substantial interest developed toward electric vehicles (EV), hybrid electric vehicle (HEV), plug-in hybrid vehicles (PHEV) and energy storage of green power grids. This catalyzed extensive usage of lithium-ion batteries (Li-ion) due to their high energy and power densities. A major concern about the use of Li-ion technology include their stability at high temperature. Li-ion cells can undergo thermal runaway leading to fire, explosion or swelling of the cell. Materials for electrolyte and separator are key component for development of safe and stable Li-ion batteries. This work focuses on development of ionogel membranes similar to gel polymer electrolytes, for Li-ion batteries with the aim of increasing the operating temperature and eliminating the safety hazards. Ionogels act as combined separator and electrolyte in one material. Mesoporous polyimide (PI) and macro and meso-porous syndiotactic polystyrene (sPS) gels are filled with ionic liquid (IL) to form the ionogel membrane. This approach combines the thermal stability and ruggedness of the polymer and the attributes of IL, e.g. extremely low volatility and non-flammability of IL. Replacement of organic carbonate based solvents by ionic liquid leads to a green battery with reduced rate of thermal runaway. The ionogel membranes show enhanced electrolyte uptake (> 90 % wt.), enhanced thermal stability (upto 270 °C for sPS and 350 °C for PI) compared to commercial polypropylene (PP) separator (160 °C). The performance of these ionogels is tested against current electrolyte-separator technology using Li⁺/ graphite half-cell at room temperature and LiFePO₄/graphite full cells at elevated temperatures.

Since the development of Li ion battery, carbonous materials e.g. active carbon have been used a major anode. However, practical capacity of active carbon reached an almost theoretical limit. Therefore, novel anode materials, such as Sn, Si etc. have been investigated to date though they are fragile after charge-discharge cycles.
It was recently reported that amorphous SiOC anode exhibited high capacity and superior cycling characteristics. The major merits are as follows. The density of SiOC is about two-thirds of Si crystal and its volume swell by battery charge-discharge can be restrained. The chemical stability and the mechanical strength of SiOC are high.
In this study, we employed a sol-gel method to deposit SiOC directly on the Cu foil as a simple and cheap way, which can be applied for large area deposition and be potentially mass-productive. The starting precursors were TEOS (Tetraethyl orthosilicate) (0.04 mol) as a Si source, and PEG (polyethylene glycol) or PDMS (polydimethylsiloxane) as a carbon source. They were mixed in ethanol (0.25mol) and water (0.25mol) to for a sol solution. Carbonized phenol particles by 800 #8451;(200 nm in diameter) were added in some experiments. The sol solution was spin-coated onto the Cu foil. We evaluated these kinds of anode by battery charge-discharge test. Pore distribution and composition was measured by small angle X-ray scattering and X-ray photoelectron spectrometry, respectively.
For SiOC film from TEOS/PEG mixture (molar ratio, TEOS : PEG = 1:1), initial capacity and that after 100 cycles were 470 mAh/g and 550 mAh/g, respectively. For SiOC film from TEOS/PDMS mixture (molar ratio, TEOS : PDMS = 1:1), initial capacity was 1000 mAh/cm² and 900 mAh/g was maintained even after 100 cycles. SiOC film showed good capacity after 100 cycles, however, we found that the capacity drastically decreased when we evaluated electrostatic capacity with current density over 200 mu;A/cm². On the contrary, SiOC film containing carbonized phenol particle did not show much decreased in the range from 10 to 1000 mu;A/cm², compared with the film with PEG or PDMS.

Expected and materialized, portable, wearable and stretchable electronic devices achieve enormous popularity in recent years. Many conceptual products, such as flexible, smart phones, intelligent bracelets and eye-catching Google glasses, appear as a state-of-the-art technology and create a fresh world where people can acquire information in a few blinks. The matchable power system is badly needed to back up the above electronic devices, which remains a challenge. Wire-shaped electrochemical storage devices, featured as flexibility and weavability, emerged and thrived in response. Wire-shaped lithium-ion batteries are suggested to be one of the most likely applied alternatives, but are not available because hindered by some down-to-earth considerations like safety, which is serious and critical for applications of wearable devices.
Here a novel wire-shaped lithium-ion battery has been produced from two aligned multi-walled carbon nanotube/lithium oxide composite yarns as the anode and cathode. The two composite yarns can be well paired to enable high safety and electrochemical properties, e.g., energy density of 27 Wh kg^-1 or 17.7 mWh cm^-3 and power density of 880 W kg^-1 or 0.56 W cm^-3 that is an order of magnitude higher than Li thin-film batteries. Such wire-shaped batteries are lightweight with a linear density of 12 mg m^-1 and flexible with the capacity to be maintained by 97% after bending for 1000 cycles. They are also super-stretchy based on a modified spring structure, and the capacity is maintained by 84% after stretch for 200 cycles at a strain of 100%.
Reference
1, Ren, J., Zhang, Y., et al. Angew. Chem. Int. Ed., 2014, 53, 7864-7869.
2, Yang, Z., Ren, J.,et al. Chem. Rev., 2015, 115, DOI: 10.1021/cr5006217, online.
3, Ren, J., Li, L., Chen, C., et al. Adv. Mater., 2013, 25, 1155-1159.
4, Ren, J., Bai, W., et al. Adv. Mater., 2013, 25,5965-5970.
5, Lin, H., Weng, W., Ren, J., et al. Adv. Mater., 2014, 26, 1217-1222.
6, Zhang, Y., Bai, W., Ren, J., et al. J. Mater. Chem. A., 2014,2, 11054-11059

Li-ion batteries have been the predominant power sources for electronic mobile devices for the last two decades, and their applications have been widened to other emerging markets, such as electric vehicles (EVs) and power storage units. To satisfy the needs for higher capacity of longer-lasting electronic devices and EVs, many researches with various kinds of materials have been investigated intensively. Among various anode materials, silicon has been extensively studied because of its higher theoretical capacity with specific capacity of 4200 mAh/g than that of the current commercialized materials of about 360 mAh/g. In this study, a core-shell structure of silicon nanocomposite with highly conductive titanium nitride coating layer was successfully synthesized using simple and neat mechanical alloying method followed by heat treatment. Both X-ray diffraction and cross-sectional scanning electron microscopy with energy dispersive spectroscopy analyses confirmed the core-shell structure of silicon alloy composite with approximately 20 nm silicide core surrounded by silicon phase covered by the titanium nitride phase. This anode material showed an excellent electrochemical performance since the stable structure and conductive coating layer.

This talk will describe a new electrode design that is intended to reduce the likelihood of thermal damage in the event of vehicle collision or other mechanical abuse. When impacted or crushed, the redesigned current collector will limit the conductivity of the battery electrode assembly and hence limit the current at the site of an internal or external short. Interesting and unexpected results were discovered during the experimental proof of concept and comparison to our model calculations. These will be discussed as well as the capacity of this architecture to improve safety by limit the shorting current that might trigger local heating and battery damage. By making individual cells inherently more abuse tolerant, the overall weight of the battery system might be reduced and batteries might be distributed in outer spaces of the vehicle that are more likely to suffer mechanical damage.
Acknowledgement: Research has been supported by the RANGE program of ARPA-E, award DE-AR0000869-1707, U.S. Department of Energy.

Intense research activity on alternative energy is stimulated by continuously increasing global demand of electric energy. Electrochemical energy storage/conversion systems represent some of the most efficient and environmentally benign technologies and the need for next generation stable, high-performance electrode materials and architectures is the driving force. The interaction between graphene-based and other nanomaterials allows develop novel architectures and tunable physical properties such as specific surface area, mechanical strength, and facile electron and ion transport via higher electron mobility and conductivity. This work presents the development and deployment of composites of graphene and encapsulated mesoporous silicon (po-Si) as practically viable, high-performance Li-Ion batteries (LIB, hereon, rechargeable secondary batteries delivering their energy to load on demand) anodes. We synthesized controlled B-doped mesoporous Si nanospheres by facile electroless etching followed by carbon coating for stable solid-electrolyte interphase (SEI) layer and wrapping with reduced graphene oxide (rGO) nanoplatelets. We have characterized their structure using a range of analytical techniques revealing surface morphology and C-Si interfaces. The electrochemical properties are measured in half-cell format in terms of cyclic voltammetry (CV), charge-discharge (or recharge) cyclability, current carrying capacity and reliability, ac impedance spectroscopy and determining energy and power density, especially the ratio of energy density/(weight x cost). Finally, these anodes with conventional LIB cathodes in full-cell format are also tested aiming to establish microscopicstructure-property-performance correlations. The knowledge gained can tap into next-generation scalable high energy density LIB for space applications as well as sodium and co-intercalated multivalent ion batteries. We acknowledge the financial support by WKU Research Foundation and NSF KY EPSCoR.

Planar thin film solid-state microbatteries are in commercial production. While, the fast development of autonomous devices pushes the demand for batteries with higher energy and power density. Moving from planar layer structures to high aspect ratio 3D electrode structures holds promise for significant energy density enhancement without much loss of power performance, or alternatively a tunable optimization and tradeoff between energy and power to fit the application. Step conformal deposition of films onto etched structures is vital for 3D batteries. Here, for the first time, the homogeneous deposition of TiO₂ film electrodes on highly structured substrates by metal-organic chemical vapor deposition (MOCVD) was investigated. The kinetic study shows that at lower deposition temperatures, the growth of TiO₂ film is a reaction controlled process. At 350 °C, almost 90% step coverage was achieved on 3D substrates (aspect ratio 3). The deposited TiO₂ film electrodes show good electrochemical activity. Compared with planar substrate with the same footprint, TiO₂ film electrodes deposited on 3D pillar substrates shows four times higher capacity due to the enlarged surface area.

Glass fiber (GF) is evaluated as a potential separator for lithium-sulfur batteries in this study. It is found that GF has highly porous structure, resulting larger liquid electrolyte uptake which enhances the electrochemical performance of the Li-S cells compared to that of commercial microporous polypropylene membranes. As a result, a capacity of 617 mAh g^-1 can be remained for the cell containing GF after 100 cycles at a current density of 0.2C (1C = 1,675 mA g^-1) which is 42% higher than that of PP. The cells containing GF can still deliver a high capacity of 577 mAh g^-1 when the current density is lowered back to 0.2C with a retention of 94%. It is probably because highly porous GF can give rise to highly soluble polysulphides species intake and slow down the rapid diffusion of polysulfides to Li anode side, leading to a higher utilization of active material and protecting of Li anode. It is demonstrated that this highly porous GF with excellent electrolyte wettability and thermal stability is a promising separator candidate for high-performance Li-S batteries.

Oxygen electrochemistry, including oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), constitutes the bottleneck of next-generation energy storage technologies such as rechargeable metal-air batteries and regenerative fuel cells. However, these heterogeneous multi-electron process significantly suffer from a sluggish kinetic and a high overpotential, which calls for high-performance catalysts for commercial applications and has stimulated intense research interest. Up to date, the precious metal or metal oxides such as Pt and IrOshy;₂ are identified as the most active catalysts, but only satisfy either ORR or OER, respectively. Additionally, their practical use is prohibited by the low abundance, high cost, and poor durability. Therefore, it is of great concern and emergence to develop highly active and also low-cost bifunctional catalysts for both ORR and OER towards practical applications.
Heteroatom-doped carbon materials are considered and investigated as the most promising low-cost bifunctional oxygen electrocatalysts. The charge delocalization induced by heteroatom incorporation results in the non-electroneutrality of catalysts and more active sites for oxygen and intermediate adsorption, thereby facilitating the ORR and OER. Herein, a novel porous nitrogen-doped graphene was facilely fabricated and demonstrated to exhibit excellent bifunctional activity. Sticky rice/melamine/MgO ternary slurry was obtained via a one-pot process by mixing the carbon source/nitrogen source/catalytic template uniformly. After high-temperature carbonization and purification, nitrogen-doped graphene material with a high surface area of 1100 m² g^-1, a large pore volume of 2.7 cm³ g^-1, and 7.6 at.% nitrogen functionalities was produced. The potential gap between the OER potential (required for 10 mA cm^-2) and the ORR half-wave potential is less than 1.0 V, which is comparable to the highly active novel metals and among the best non-metal materials. This work sheds light on the utilization of biomass for advanced and low-cost energy materials for sustainable next-generation batteries.

A new bilayer nanostructure of manganese oxide is developed by two-step hydrothermal reactions. Much higher mass loading of manganese oxide is successfully maintained (~2.4 mg cm^-2) through this new type of nanoarchitecture. In the meanwhile, the desired high specific surface area, good conductivity and ion accessibility are obtained, therefore giving rise to significantly improved electrochemical performance for manganese oxide (e.g., specific capacitance of 559.5 F g^-1 and excellent cycle ability). By growing the second layer of MnO_x on the Ni foam current collector that is pre-covered by a MnO₂ substrate layer, uniformly thin and continuous nanosheets from the second layer MnO_x with excellent surface coverage and open mesoporous structure are obtained, leading to large surface area and fast charge transfer. This novel architecting explores the new potential of manganese oxides as high performance supercapacitor electrodes.
This work is published on the Journal of Power Resources, 2015 (Journal of Power Sources 286 (2015) 394-399).

Efficient bifunctional catalyst for ORR and OER is highly desirable due to its wide applications including fuel cells and rechargeable metal air batteries. Despite the extensive effort, non-precious metal based catalysts with comparable activity to noble metals are still challenging. Here we report a one-step wet-chemical synthesis of mesoporous cobalt oxides with Ni or Mn dopant through inverse micelle. Various characterization techniques including PXRD, N₂ sorption, TEM and SEM confirmed the successful incorporation of Ni or Mn into Co₃O₄ spinel structure and the formation of Co-Ni(Mn)-O solid solutions. Also the mesoporosity was well maintained. Among these catalysts, cobalt oxide with 5% Ni loading amount demonstrated the best activity, with an overpotential of 399 mV for ORR (at 3 mA/cm²) and 381 mV (at 10 mA/cm²) for OER, on a par with the benchmark Pt/C and Ir/C catalyst. Furthermore, our catalyst showed better durability than the precious metal catalysts with negligible activity decay throughout 24 hours. After carefully investigating the catalysts through XPS and CV analyses, we proposed the redox activity of Co³⁺ to Co⁴⁺ was crucial for OER performance, while the population of surface oxygen vacancies determined the ORR activity. These findings could provide a guideline for future development of easily prepared, inexpensive and highly active electrocatalysts.

Electrochemical double-layer supercapacitors (EDLCs) have recently received a great attention in the field of electrochemical energy storage and conversion because of their high power capability and long cycle-life. Elbit Energy has developed a cutting edge, high power, aqueous supercapacitor with customizable characteristics and dimensions. This innovative “green” technology exhibits a new level of efficiency and power density. Elbit Energy EDLCs are based on activated carbon and aqueous potassium hydroxide (KOH) electrolyte in stacked thick-electrode EDLCs. One of the greatest advantages of this electrode preparation method is that it is binder-free.
Electrochemical impedance spectroscopy (EIS) in a wide range of frequencies is routinely used in SCs research, yet a thorough analysis of the spectra is not usually performed. Here presented a programming based technique that finds an analytical form of the distribution function of relaxation times (DFRT) of the system. The analysis is based on a unique computer program, Impedance Spectroscopy Genetic Programming (ISGP), which finds the best fitted model to the measured data. The outcome of the EIS analysis is an analytic function, comprised with two or three peaks, which can be assigned to different processes taking place in the tested samples. It allows modeling of the supercapacitor state of health, particularly composition changes in the electrode material and identifies various structure and aging defects.

To date, graphene-based supercapacitors, a promising technology for energy storage systems, are limited by their low energy density, which is a serious disadvantage compared to commercial batteries on the market. Specifically, a poor specific capacitance due to a lack of Faradaic reactions and porous structures in the electrode has significantly limited their successful use in energy storage. Herein, we demonstrate a new strategy to produce a high-capacitive electrode that consists of hierarchically interconnected porous structures and sufficient Faradaic reactions along with an oxygen-functionalized reduced graphene oxide electrode (denoted as PRGO-O electrode) produced via a ZnO template-assisted alkaline treatment. By simply immersing cast ZnO/reduced graphene oxide (RGO) samples into an alkaline solution, the original ZnO-occupied spaces remain intact as hierarchical mesoporous structures located between macroporous RGO interlayers and supply sufficient electric porous channels. Our alkaline treatment approach effectively and easily changed the oxygen-poor surface into an oxygen-rich surface: “The introduced oxygen-functionalized groups along the porous channels in the RGO-based electrode can serve as Faradaic active sites, which are required for high capacitance and better energy density.” Consequently, using the PRGO-O electrode as a hybrid supercapacitor, we were able to achieve a high specific capacitance of 337.2 F g^-1 in the aqueous electrolyte with an outstanding energy density of 34 W h kg^-1 at the highest power density of 24 kW kg^-1, which is comparable to those of lead-acid batteries (25-35 W h kg^-1). Throughout this work, we clearly prove that the RGO-based electrode can exhibit comparable energy density to commercial batteries when modified using Faradaic active species with interconnected pores. Additionally, our achievement presented here opens up an effective solution for designing a high-capacitive and high-rate electrode for high performance supercapacitors.

Rechargeable microbatteries with arbitrary shape and functionality will open new avenues to autonomous microdevices, including micro-robots, sensors, and well beyond. Here, we combine laser micromachining and microscale 3D printing to create lithium ion microbatteries in square, ribbon, and donut shapes with lateral dimensions ranging from 1-10 millimeters. These rechargeable microbatteries exhibit high capacity and discharge rates (up to 100C). We highlight flexible modules interconnected with ribbon cells, stretchable modules interconnected with donut cells, and other designs in which other components (resistors, transistors, LEDs and photosensors) are directly integrated into the batteries.

Recently, alkaline anion exchange membrane fuel cells (AEMFCs) have received increased attention due to their advantages over the PEMFCs. It is essential to understand the transport property of these AEMs for better performance. The water and ion transport in the AEMs were investigated systematically by in-situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The relationship between the water diffusion and the membrane microstructure was first discussed. The diffusion coefficient is highly dependent on the charge density and hydrophilicity. A fundamental understanding of the ion transport mechanism in AEMs was further evaluated by monitoring the anion exchange process and the ion competition experiments.

Sodium-ion-battery is one of potential solution for the resource shortage of Li to overcome. Newly developed Na cathode material: Na₄Co₃(PO₄)₂P₂O₇: is attracting much attention due to its high rate, high capacity, and high voltage properties among sodium ion battery materials. However, detailed its electronic structure and its charging during charge/discharge, is still open issue. In this present paper, we carried out precise first principles calculations within GGA+U formalism. Focusing on the de-sodium behavior of Na₄Co₃(PO₄)₂P₂O₇. Until NaCo₃(PO₄)₂P₂O₇, de-sodium occurring with redox reaction from Co²⁺ to Co³⁺. However, after this Na content, redox reaction occurring from oxide oxygen 2p orbitals, not from Co³⁺ to Co⁴⁺. A great structural shrink can be occurred de-sodium process between NaCo₃(PO₄)₂P₂O₇ to Co₃(PO₄)₂P₂O₇. These can be the critical factor prohibiting de-sodium from NaCo₃(PO₄)₂P₂O₇ to Co₃(PO₄)₂P₂O₇ in Na₄Co₃(PO₄)₂P₂O₇.

Among the materials for negative electrode of lithium-ion batteries (LIB), Si possesses the largest theoretical capacity (3579 mA h g^-1 at room temperature for Li₁₅Si₄) besides Li. However, Si suffers from the cracking or pulverization due to volume expansion through the lithiation process. In order to solve this problem, nanostructured Si such as nanowires, nanotubes, or nanoparticles have been attempted as anodes.
Considering the volume expansion of +280% during lithiation from Si to Li₁₅Si₄, and expecting the effective usage of the electrode layer space, the ideal initial occupancy of Si is estimated to be ~ 25%. From this viewpoint, columnar-microstructured Si (CMS) materials seem to be good candidates. In this study, we tested Si nanoneedles, a type of CMS, for evaluation of their performance as anode for LIB.
Nanoneedles of an averaged height of 15 µm were prepared by a cryogenic plasma etching process in a SF₆/O₂ mixture gas on a Si wafer.[1] The resulting nanoneedle- structured wafer piece was put in a coin cell with conventional liquid electrolyte (EC/PC/3DMC + 1M LiPF₆) and a Li foil to form a half-cell. The galvanostatic cycling of the half-cell has confirmed excellent stability (with quantitative coulombic efficiency) for 380 cycles or more, under a capacity limit of 2665 mA h g^-1, which corresponds to three quarters of theoretical capacity of Si. It is notable that this nanostructured Si functions as a stable anode material even though it was packed in the half-cell together with the Si wafer bare substrate.
Scanning electron microscope images of the anode layer after successful long cycles revealed monotonous surface morphology where the needles filled out the space. Generally, the cracking occurs in a Si material at a position of discontinuous degree of lithiation. We speculate that the gradual increase of diameter of the Si needles along the depth allows gradual change of degree of lithiation along the depth, preventing formation of cracks.
[1] R. Dussart et al., J. Phys. D: Appl. Phys. 38 (2005) 3395.

Graphene, an atomic single layer of honeycomb carbon lattice has attracted great attention due to its superior electronic conductivity, high surface area, chemical and physical stability. Extensive research has been devoted to the fabrication of graphene-based nanostructures for lithium ion batteries. Silicon has been one of the most attractive materials to be coupled with graphene due to its high theoretical capacity (~4000 mAh/g), which is 10 times higher than that of the commercialized graphite anode (372 mAh/g) and is attributed to its very high lithium uptake (Li_4.4Si) through alloying. However, it suffers from a rapid capacity fading because of its enormous volume change (~ 400%) during charge/discharge. So, a lot of methods to lessen the volume expansion of Si and its corresponding loss of electronic contact have been devised.
The encapsulation of graphene or RGO (Reduced Graphene Oxide) around Si definitely looks very promising to solve lots of problems induced by the volume expansion of Si. So, in this work, we tried to make carbon-encapsulated Si particles sandwiched between RGO layers to minimize the volume expansion and electronic contact loss of Si particles by utilizing RGO and carbon coating layer as a cushioning media and robust electronic pathway, respectively. Besides the aforementioned effect, such a sandwich structure could avoid aggregation or stacking during charge/discharge, which enabled to maintain the initial active surface and open channels for ion transport. . This achievement demonstrated the potency of this novel hybrid design based on two dimensional materials including graphene or RGO for extremely reversible energy conversion and storage.

Li-S batteries have attracted great research interest owing to the abundance, low cost and high theoretical capacity of sulfur. However, there are still a number of issues needed to be addressed before the commercialization of Li-S batteries. One of the toughest problems is that the highly soluble intermediates (Li₂S₈ -Li₂S₆) can diffuse to the negative electrode, where they are reduced to Li₂S and deposit, resulting in the capacity fading of Li-S batteries. Herein, a nitrogen-doped carbon membrane is applied as an interlayer between the sulfur cathode and the separator and the performance of Li-S batteries has been greatly improved. The interlayer functions as both an “upper current collector” and a “polysulfide stockroom&’&’ to retain the capacity. Furthermore, the enhanced conductivity and strong adsorption between the polysulfide and the interlayer owing to the nitrogen doping make the nitrogen-doped carbon membrane better than commonly used carbon paper as an interlayer. The nitrogen-doped carbon membrane is derived from pyrolysis of a filter paper in ammonia gas. The pyrolysis and doping process is studied and their influence on the battery performance will be reported. Our study opens a new route to design carbon nanomaterials with controlled specific surface area and nitrogen doped content for enhancing cyclability of Li-S batteries. Meanwhile, the sulfur cathode used here is nickel foam electrodeposited with sulfur nanoparticles, avoiding noxious binder and complicated fabrication process. Thus, we present a simple, economical and environmentally friendly method to fabricate sulfur cathodes.

The ever-growing concerns on fossil fuel crisis and ecological deterioration have attracted human beings&’ attention to the utilization of renewable energies such as solar and wind energies. However, these energies are produced erratically or intermittently, therefore, energy storage, especially electrical energy storage has become one of the essential issues which lead to the better utilization of sustainable energies in the future. Among various energy storage technologies, supercapacitors (SCs) hold great promise in broad applications such as portable electronics, smart grids, and electrical vehicles. Compared to LIBs which have been widely used and possess a high energy density, SCs exhibit much higher power, longer cycling life and shorter charge duration, making them a primary choice in applications where safety and high power are highly required. However, SCs often suffer from poor energy density. So far, high surface area carbon-based materials (e.g., activated carbon) have been most commonly used as electrode materials in SCs and can only deliver a specific capacitance of sim;150 F g^minus;1, by storing charge on the surface of materials forming an electric double layer. Thus, a low energy density (<10 Wh kg^minus;1) is usually obtained. By comparison, pseudocapacitors based on inorganic non-carbon based materials store much higher charge (>1000 F g^minus;1) through reversible faradaic reactions. However, the performance of metal oxides is hampered by agglomeration, low electrical conductivity and slow redox rate, so a low capacitance and a poor rate capability is often observed. Therefore, it is essential to design and build novel architectures with efficient ion- and electron-transport pathways as well as robustness to further improve the electrode kinetics and integrity, which is highly demanded by high-performance supercapacitors.
Herein, we report a composite material of MnO₂ nanocrystals/hierarchically porous carbon spheres with partially graphitized surface (MnO₂/C), which exhibits excellent electrochemical performance for asymmetric supercapacitors. Such a composite with unique structure possesses several features favoring high-performance electrodes: (i) the interconnected hierarchically porous structure with micro- and meso-pores not only provides high surface area resulting in high capacitance but also facilitates ion transport leading to high rate capability; (ii) the partially graphitized carbon improves the electron conductivity which further increases high rate capability; (iii) the in-situ growth of MnO₂ on carbon spheres ensures an intimate contact between the two components, providing the composites with both high rate and robustness. Moreover, the micrometer-sized composites can be easily fabricated into electrodes by a slurry-coating process compatible with existing battery manufacturing, which makes it a promising material for future practical applications.

Wearable energy-storage devices have attracted great attention in displays, health monitoring devices, and electronics. The expanding requirements of the wearable devices, such as high efficiency, cheap price, light-weight, and flexibility, have facilitated many attempts to develop flexible alternative electrode materials. In this study, we have fabricated the flexible hybrid electrode using the hydroquinone (HQ)-activated CoO@Polypyrrole (PPy). The electrodes, structured the flower-like CoO wire array grown on nickel foils, were prepared via hydrothermal process for a porous structure with high-surface area and large porosity. Then, to enhance the conductivity of the flower-like CoO wire electrode, a polypyrrole as conducting polymer was integrated into the CoO wire array as a thin layer by chemical polymerization. Finally, the flower-like CoO@PPy powders collected from the film were mixed with HQ-PVA gel to fabricate the flexible hybrid electrode. We have used the hydroquinone as an electrochemically active compound on the flexible electrode of a supercapacitor. Such flexible electrode exhibits an improved electrochemical performance, high specific capacitance, and excellent cycling stability owing to the synergistic contribution of composite materials and the capacitive activity of hydroquinone.

Powders of La₂O₃ were mixed with mechanical ball-milling technique (MA) adding TiO₂, to improve the electrochemical performance as a storage material. Microstructures, morphologies and electrochemical results were investigated using TEM, X-ray diffraction (XRD), Cyclic Voltammetry and Potentiodynamic studies. Results showed that, the samples with TiO₂ content affected the capacity of response. The alloys exhibit a superior capacity and stability adding TiO₂. The milling ball to powder weight ratio was kept 5 to 1 for all experimental runs. Milling intervals were 0, 2 and 4 hrs; using alternate cycles of 30 minutes milling and 30 min resting. The nanostructure TiO₂ powder, improve the samples to design a better electrode. TiO₂ has significant influence on electrochemical performance of electrodes. Electrochemical experiments were performed on ACM Instruments Gill AC and a typical three-electrode setup was constructed to measure the electrochemical properties of the working electrode; here, platinum was used as the counter electrode and calomel was used as the reference electrode. Structures of the samples were analyzed by digital image tools.

Analytical imaging using X ray Compton scattering is a new method that allows the in-situ observation of a sample interior (like Li-ion battery) in operando conditions. Due to the high energy of incident radiation, this technique is able to look deep inside the large samples. High intensity of synchrotron beam provides the adequate experimental statistics even in case of the high collimation of incident and detected beam.
This technique was recently applied to a commercial lithium coin cell (CR2032) under discharge process [1]. Analysis of a time and position dependent spectrum shape allows to present the lithium migration behaviour in a quantitative manner. By scanning the focused high energy X ray beam throughout the body of a battery, the variable amount of mobile Li ions is monitored by detecting Compton scattered X rays. Registered intensity is not only proportional to the electron density, but also contains valuable information about the scattering material type in the shape of Compton peak. Therefore, detected spectra of scattered X rays are analysed in terms of its line shape parameter (called S parameter), which varies with material composition and is employed for estimating ion concentration.
We present the new setup and methods create to improve the experimental and analytical abilities of our system. By using lately developed Ni compound refractive lens we will be able to improve the experimental resolution through the stronger collimation of incident beam together with the significant increase of the incident beam intensity [2]. Using a 9 pixel Ge SSD allows also to enhance the statistics for registered spectra either. In order to improve the S parameter determination accuracy, the new Monte Carlo procedure for multiple scattering simulation dedicated to highly collimated geometries was developed [3].
This work is supported by the Development of Systems and Technology for Advanced Measurement and Analysis program under Japan Science and Technology Agency.
[1] M. Itou et al., J. Synchrotron Rad. 22, 161-164 (2015)
[2] A. Andrejczuk et al., J. Synchrotron Rad. 21, 57-60 (2014)
[3] M. Brancewicz et al., to be published soon...

Two dimensional layered MoS₂ nanostructure has emerged as a promising candidate of anode material in lithium ion batteries (LIBs). Herein, we summarize our work on MoS₂ nanosheets decorated on different carbonaceous materials (Carbon nanotubes (CNTs), onion-like carbon (OLC), graphene, vertical graphene nanosheets (VGNS) and graphene aerogel) to synthesize various hierarchical architectures as anode of LIBs via a one-step solvothermal/hydrothermal method. In addition, vertical aligned MoS₂ nanoleaves were grown on graphene oxide film by chemical vapor deposition process. These carbonaceous materials were employed as the backbone to enhance MoS₂ electrochemical performance, in terms of specific capacity, rate capability, cycle stability and initial coulombic efficiency (CE). For example, MoS₂/VGNS nanostructure can deliver a specific capacity of 1,277 mAh g^-1 at a current density of 100 mA g^-1, and it also can retain a capacity of 1109 mAh g^-1 after 100 cycles at a current density of 200 mA g^-1. Vertical aligned MoS₂ nanoleaves on graphene oxide film electrode can deliver a capacity of 727 mAh g^-1 at the current density of 2000 mAh g^-1 even after a long cycling period of 940 cycles (1000 mA g^-1 at first 500 cycles and 2000 mAh g^-1 at last 440 cycles), suggesting excellent long cycle stability at large current density. Although the initial CE of the MoS₂/carbonaceous electrode can reach up to ~70%, it was increased to 97.6% via a simple pre-lithiation method with MoS₂/OLC nanostructure. The enhanced electrochemical performance was attributed to the maximized exposed active sites, reduced ion diffusion length and accommodated volume change during the lithiation/delithiation process in these unique hierarchical nanostructures. We anticipate these MoS₂ based three-dimensional hierarchical nanoarchitectures will be promising anode materials in future generation LIBs.

The extensive volume change and continuous consumption of active electrode materials due to the repeated formation of a solid electrolyte interface (SEI) layer during charge-discharge cycles are two important topics to be considered for the development of new nanostructured electrodes for highperformance lithium ion batteries (LIBs). In this work, layer-stacked cobalt ferrite (CoFe₂O₄) mesoporous platelets with two different thicknesses are synthesized, and their electrochemical performance as anodes for LIBs is evaluated. We find that the thickness of the platelets has a great impact on the specific capacity and stability. The thicker platelets (about 2 mm) enable a reduction of SEI-induced consumption of active materials and lead to an overall electrochemical performance superior to that of thinner ones. At a high rate of 5 A g^-1, after an initial drop, the capacity of thicker platelets continuously increases in the following 500 cycles and reaches saturation around 950 mA h g^-1, then gradually decreases and remains at 580 mA h g^-1 after 2000 cycles. The high capacitance, outstanding rate performance and stability of thick platelets can be attributed to the special configuration of the layer-stacked mesoporous platelets which provides sufficient interlayer space for volume expansion, and enables the formation of a stable SEI layer during the cycling.

Porous carbon materials have long been the material of choice for electrodes utilized in energy storage applications due to their combination of good electrical conductivity, chemical inertness and low bulk material density (~2 g/cm³). The high surface areas (> 1000 m²/g) that are useful for many energy storage applications are typically achieved via nano-scale porosity generation. Herein, we describe a facile strategy to synthesize hierarchical porous carbon (HPC) materials employing three distinct templating strategies to purposely imbue porosity on all three different porosity regimes: micro- (<2 nm), meso- (2-50 nm) and macroporosity (>50 nm). We will show how optimization and modification of this strategy has resulted in HPCs with very large specific surface areas (>2500 m²/g) along with ultra-high micro/mesopore volumes (>10 cm³/g)—the combination of which are rarely seen in porous carbon materials. We will also demonstrate how easily tunable the textural characteristics are for these HPC materials; providing a route towards tailorable materials for specific applications. More importantly, we will show how relatively inexpensive the constituent components are in the synthesis scheme and how many of the processes utilized are already in commercial use. Finally, we will demonstrate how such a tunable HPC structure can be employed in energy storage applications such as supercapacitors by demonstrating their performance in electrochemical devices.

High capacity silicon electrodes are expected to replace today&’s carbon based electrodes if
the fracture problem associated with volume expansion of silicon upon lithiation can be overcome.
One of the approaches to mitigate fracture is to create core-shell structures where the shell
contains the silicon core from disintegration. We report the synthesis, characterization, and
performance of a binder-free negative electrode for Li-ion battery, consisting of renewable
biopolymer lignin and nano-sized silicon nanoparticles. By mixing, coating, and subsequent
pyrolization, we synthesized uniform interconnected core-shell composite film of Si/C directly on
current collector, allowing for the assembly of coin-cells without the need for extra binder and
conductive carbon. The silicon/pyrolized lignin electrode (Si-pLig) showed comparable charge
capacity to silicon electrode prepared with conventional binders and displayed stable rate
performance from 0.1A/g to 0.8A/g. Moreover, the Si-pLig electrode can be reversibly cycled at
0.3A/g with 96.8% capacity retention over 50 cycles, suggesting that the binder free interconnected
Si/C core-shell structure is promising for high capacity lithium ion battery applications.

Nowadays, the hybrid compounds have been investigated for the use in a supercapacitor. It has been reported that the hybrid electrodes with the metal oxides or conducting polymers and carbon-based materials present the synergistic contribution effects on their supercapacitive performance. In this work, the hybrid electrodes for a supercapacitor have been prepared with the pseudo-capacitive materials and the electrical double-layer capacitor (EDLC) materials. At first, the graphene template has been fabricated with electrochemical reduction of graphene oxide powder obtained by the modified Hummer&’s method. For utilizing the pseudo-capacitive materials of polypyrroles on the EDLC materials of graphene, the chemical polymerization process has been used. The three-dimensional structures of nickel-oxide/polypyrrole/graphene have been monitored and their electrical performance for a supercapacitor has been evaluated. It has been found that the electrical conductivity improved by hybriding the materials contributes the enhancement of specific capacitance on the electrode.

Various metal oxides have been investigated as anodes for lithium ion battery applications due to their high theoretical capacities. Germanium oxide has attracted much attention because of high theoretical capacity derived by conversion and alloying reactions. Development of high-capacity GeO₂ anodes, however, has been hampered by their poor stability caused by a huge volume change and irreversible conversion reaction of GeO₂ during Li⁺ insertion/extraction. To solve these problems, we report mesoporous composite materials (m-GeO₂, m-GeO₂/C and m-Ge-GeO₂/C) with large pore size which are developed by a simple block copolymer directed self-assembly. m-Ge/GeO₂/C shows greatly improved coulombic efficiency, high reversible capacity (1631 mA h g ^-1) and stable cycle life compared with the other mesoporous and bulk GeO₂ electrodes. m-Ge/GeO₂/C electrode exhibits one of the highest areal capacities (1.65 mA h cm^-2) among previously reported Ge and GeO₂-based electrodes. The superior electrochemical performance in m-Ge/GeO₂/C arises from the improved kinetics of conversion reaction due to the synergistic effects of the mesoporous structures and the conductive carbon and metallic Ge. The detailed aspects and direct evidence for reversible conversion reaction (re-oxidation or Ge) are investigated by electrochemical evaluation, ex-situ X-ray diffraction, and in-situ X-ray absorption spectroscopy. We present that the tailoring nanostructures and composition of GeO₂ anodes can significantly enhance their electrochemical performance. Thus, this work paves the way toward the development of high-capacity conversion anodes with high reversibility and cycle stability.

Recently, several rechargeable batteries (1-4) have been discussed in the literature for large scale energy storage applications. Among them low toxicity battery such as Zn-Cu has been given prominence. In this battery, by having redox electrolyte along with nanoparticles of 5 nm to 100 nm having a large surface area, a continuous and convective flow of the redox species has been generated that results in the higher power and energy density; this situation augments the external storage of the redox couples and the associated flow systems. The ion cross over problem that results in the discharge and unrechargeable characteristics have been overcome using a thin membrane. We demonstrate that the redox species is convectively transported from the measurements of cyclic voltammetry and differential pulse voltammetry. Initial measurements of stable redox couples of Zn, Cu and Fe showed a positive gain in power and energy densities. With Zn and Cu, there is an advantage of non-dendritic growth under the conditions of the experiment, plus a large surface area material codepositing enhancing the performance of the flow battery. The specific energy of Zn-Cu redox couple is estimated to reach a value of 42.5 Wh/kg which is higher than flow battery giving 25-30 Wh/kg (3). It is predicted by a controlled trajectory of the nanoparticles, the specific energy value can be further enhanced.
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1. X. Dong, Y. Wang and Y. Xia, Daniell Cell with a Li-ion exchange Film. Sci. Rep. 4, 6916; DOI:10.1038/srep06916 (2014)..nature.com/scientificreports
2. P. Novak, K. Mueller, K.S.V. Santhanam and O. Haas, Chem. Rev., 97, 207 (1997)
3. K.S.V. Santhanam and G. Lein, Encyclopedia of Nanomaterials, The Chemical and Electrochemical Power of Nanomaterials, Encyclopedia of Nanoscience and Nanotechnology, Vo. 24, p.249, (2011)
4. B. Dunn, H. Kamath and J.M. Tarascon, Electrical Energy storage for the grid, Science, 334, 928 (2011)

Providing large-scale electricity storage for the grid is particularly challenging due to the massive scale and aggressive cost metrics required for adoption. One recent battery type, the liquid metal battery (LMB), is attractive due to its simple construction, its circumvention of solid-state failure mechanisms and resultantly long lifetimes, and its particularly low levelized cost of energy [1]. Though many of the advantages of the system derive from the fully molten state of its battery components, this requirement drives high operational temperatures that complicate cell design and lower round-trip efficiency. Here we investigate the binary NaOH-NaI salt system for low-cost and low-temperature sodium-based LMBs. This high conductivity system (0.5 S/cm) is here found to combine low eutectic melting temperatures (220°C), suitable electrochemical window (1.8 V), and unusually good stability versus sodium metal (i_leakge 0.34mA/cm²). Initial cycling results of the Na||Pb-Bi system confirm these properties with over 100 cycles achieved in proof-of-concept cells. In addition to exploring the electrochemical properties, we also provide a detailed thermal study of the system with a newly proposed phase diagram containing new compounds corroborated by crystallographic study. This binary salt phase data was then fit to a two-sublattice thermodynamic solution model in FactSage thermochemical software to provide a starting point for study of higher order systems. Our results highlight the opportunity of this new type of molten salt system to serve as an electrolyte in low-temperature sodium LMBs.
[1] Kim, H., D. A. Boysen, et al. (2012). "Liquid Metal Batteries: Past, Present, and Future." Chemical Reviews

This is the first report of a hybrid sodium ion capacitor (NIC) with the active materials in both the anode and the cathode being derived entirely from a single precursor: peanut shells, which are a green and highly economical waste globally generated at over 6 million tons per year. The electrodes push the envelope of performance, delivering among the most promising sodiation capacity - rate capability - cycling retention combinations reported in literature for each materials class. Hence the resultant NIC also offers a state-of-the-art cyclically stable combination of energy and power, not only in respect to previously published NICs but also as compared to Li ion capacitors (LICs). The ion adsorption cathode based on Peanut Shell Nanosheet Carbon (PSNC) displays a hierarchically porous architecture, a sheet-like morphology down to 15 nm in thickness, a surface area on par with graphene materials (up to 2396 m²g^-1) and high levels of oxygen doping (up to 13.51 wt%). Scanned from 1.5 - 4.2 V vs. Na/Na⁺ PSNC delivers a specific capacity of 161 mAhg^-1 at 0.1A g^-1 and 73 mAhg^-1 at 25.6 Ag^-1. A low surface area Peanut Shell Ordered Carbon (PSOC) is employed as an ion intercalation anode. PSOC delivers a total capacity of 315 mAhg^-1 with a flat plateau of 181 mAhg^-1 occurring below 0.1 V (tested at 0.1 Ag^-1), and is stable at 10,000 cycles (tested at 3.2 Ag^-1). The assembled NIC operates within a wide temperature range (0 - 65°C), yielding at room temperature (by active mass) 201, 76 and 50 Wh kg^-1 at 285, 8500 and 16500 W kg^-1, respectively. At 1.5 - 3.5 V, the hybrid device achieved 72% capacity retention after 10,000 cycles tested at 6.4 Ag^-1, and 88% after 100,000 cycles at 51.2 Ag^-1.

Prussian Blue, KFe[Fe(CN)₆]middot;xH₂O, is a dark blue pigment known since the early 18th century.[1] It is easily synthesized by room temperature co-precipitation in aqueous media. Although it was initially investigated as synthetic pigment in painting, other applications were soon discovered due to the magnetic,[2] optical[3] and adsorption properties[4] it exhibits. In the 70's, Neff showed its activity as electrode material in electrochromic devices.[5] This study became the trigger for a wide number of later investigations as cathode material both in lithium,[6],[7] and more lately, in sodium ion batteries.[8] Its good electrochemical performance being due to the strong 3D metal-organic framework that Prussian Blue and its analogues possess with tunable and open channels that allow rapid insertion/deinsertion of species.[9]
Due to the increasing interest of new less expensive and more environmentally friendly battery technologies, such as the sodium ion batteries (SIB), we became interested in the sodiated phase of Prussian Blue, ideally NaFe[Fe(CN)₆]middot;xH₂O,[10] as the presence of sodium ions already in the crystal structure could facilitate the insertion/deinsertion of these alkali ions. Several studies have already proved its feasibility as cathode for SIB, however, these have been performed using different electrolytes and binders, making the comparisons difficult.[8],[11],[12] Herein we will present the study on the optimization of the electrolyte and binder composition in the electrochemical behaviour of this sodium system.
Moreover the totally reduced phase, sodium Prussian White, ideally Na₂Fe[Fe(CN)₆], is an ideal cathode material for full batteries with sodium free anode materials. The full occupancy of cavities by sodium ions results in a minimal H₂O content, which has been demonstrated to provoke an enhancement on the electrochemical features compared with Prussian Blue.[13],[14] A novel synthesis methodology, using milder conditions compared to others already reported, will be presented. The material exhibits up to 150 mAh/g when cycled at 85.4 mA/g vs. Na⁺/Na in organic media.
[1] N.N. Greenwood et al. Chemistry of the Elements, p. 1094 (Chapter 25).
[2] H. Tokoro et al. Dalton Trans. 40 (2011) 6825.
[3] K. Itaya et al. J. Appl. Phys. 53 (1982) 804-805.
[4] S.S. Kaye et al. J. Am. Chem. Soc. 127 (2005) 6506-6507.
[5] V. D. Neff. J. Echem. Soc. 125 (1978) 886.
[6] N. Imanishi et al. J. Power Sources 79 (1999) 215-219.
[7] L. Shen et al. Chem. Eur. J.20 (2014) 1-5.
[8] Y. Lu et al. Chem. Comm. 48 (2012) 6544.
[9] D. Ellis et al. J. Phys. Chem. 85 (1981)1225.
[10] Piernas-Muñoz M. J. et al. J. PowerSources (submitted).
[11] You Y. et al. En.Environm.Sci., 2014, 7, 1643.
[12] Wu X. et al. J. Mat. Chem. A, 2013, 1, 10130-10134.
[13] Takachi M. et al. Appl. Phys. Express, 2013, 6, 025802.
[14] Wang L. et al. Angew. Chem. Int. Ed., 2013, 52, 1-5.

Driven by the need to access higher energy densities beyond those offered by Li-ion batteries, rechargeable Mg batteries have been receiving increased interests. Mg metal has a high volumetric capacity (3833 vs. 2046 mAh cm^-3 for Li), is non-dendritic and offers an opportunity for battery cost reduction owing to its abundance in the earth crust (5^th most abundant element). However, several technical challenges that hamper realizing practical rechargeable Mg batteries are currently present. For example, the absence of robust and practical high voltage/high capacity cathodes currently limits the energy density which could be harnessed using these systems.^[1] Another major hurdle is caused by the type of electrolytes currently used in Mg batteries. At its very core, is the limitation induced by the incompatibility of Mg metal with simple ionic salts and non-ethereal solvents. Therefore, electrolytes based on complex ethereal solutions of Grignard/organo-halo/halo-Mg reagents were found to be compatible with Mg metal and for over than two decades were used as platforms to prepare highly stable Mg electrolytes. However these were found to be highly corrosive ^[1] and a need for simple-type Mg salts exists in order to improve the transport and solubility properties. We have been pioneering the development of a new class of electrolytes based on a novel bottom-up design strategy that don&’t use the known systems and offer halogen free and non-corrosive simple-type Mg salts. Herein, we will outline the current status with rechargeable magnesium batteries with focus on the most recent critical developments and our electrolyte design concepts that guided creating a new paradigm using boron-hydrogen salts. We will explain how these new concepts guided preparing and demonstrating the only ionic, simple-type salts known to be compatible with Mg metal. We will also discuss the remaining challenges present with Mg batteries and offer a future perspective towards overcoming these.^[2,3,4,5]
References
[1] a) H. D. Yoo, I. Shterenberg, Y. Gofer, G. Gershinsky, N. Pour, D. Aurbach, Energy Environ. Sci. 2013, 6, 2265-2279; b) R. Mohtadi, F. Mizuno Beilstein J. Nanotechnol.2014, 5, 1291-1311
[2] R. Mohtadi, M. Matsui, T. S. Arthur, S.-J. Hwang, Angew. Chem. Int. Ed.2012, 51, 9780 -9783
[3] a) T. J. Carter, R. Mohtadi, T. S. Arthur, F. Mizuno, R. Zhang, S. Shirai, J. W. Kampf, Angew. Chem. Int. Ed.2014, 53, 3173-3177;
[4] O. Tutusaus, R. Mohtadi, ChemElectroChem.2015 DOI: 10.1002/celc.201402207;
[5] O. Tutusaus, R. Mohtadi, T. Arthur. F. Mizuno, Angew. Chem. Int. Ed.2015, DOI: 10.1002/anie.201412202R3.

As the energy sector moves towards renewable energy and electrification of transportation, there is a greater need for inexpensive electrical energy storage. In order to reduce the cost of batteries, many different strategies can be employed; including improving the manufacturing process, increasing the energy density, and using lower cost materials. It is possible that a battery based on a chemistry using Mg or Ca could have both improved energy density and reduced materials costs due to the abundance of these elements. However, there are many challenges that need to be solved to practically implement these chemistries; such as interfacial film formation, slow diffusion, incompatibilities between electrolytes and materials, and finding a high voltage high capacity cathode. In order to minimize issues with compatibility between the electrolyte and the inactive components of the cell, we developed a cell using a standard coin cell format with graphite foil spacers and a capacitive counter electrode for testing potential cathode materials. Using this type of cell we have identified a class of materials that can achieve higher voltages for both Mg and Ca based systems as compared to Mg in chevrel, but at reduced capacity. Through the use of X-ray absorption near edge spectroscopy (XANES), X-ray diffraction (XRD) and compositional analysis we determined that the electrochemical capacity is due to the intercalation of Mg and Ca into the structure. To further understand the issues with practical implementation we have moved towards pairing these high voltage cathode materials with low voltage anode materials such as Mg metal and metals that react with the active ion. Despite our efforts, there are still difficulties that remain to be solved involving the formation of undesirable interphases and lack of passivation in these full cells, which limit the voltage and cyclability.

Magnesium (Mg) batteries are a promising battery technology due to high gravimetric and volumetric capacities of Mg anode, additional benefit is high natural abundance of Mg All this could lead to significantly cheaper non-aqueous batteries with energy densities comparable or even better than, state-of-the-art Li-ion batteries. Although pioneer work on prototype Mg battery system was carried out by Aurbach et al (reference) already in 2000, several challenges remain to be solved. The major contemporary challenges are development of non-corrosive electrolytes with high oxidative stability and design of high energy cathode materials.
In this contribution we present a novel approach, use of stable polymer organic cathode coupled with non-nucleophillic electrolytes and Mg powder anode. All of our electrochemical test were carried out in two electrode modified Swagelok laboratory cells. Capacities between 150 and 200 mAh/g at a voltage from 1.5 - 2.0 V vs. Mg/Mg²⁺ with a stability over 100 cycles were obtained with the possibility of achieving high rate capabilities that are inherent to some organic cathodes. The present results pave the way for the use of other organic active materials and the further development of electrolyte systems. In particular, by broadening the range of organic solvents used, we expect that even better stability and capacity of organic materials can be achieved.

The cathode material Ag₂VO₂PO₄ has recently attracted research interest for biomedical Li-ion batteries to power implantable cardiac defibrillators. A high capacity of up to 270 mAh/g could be achieved for Li/Ag₂VO₂PO₄ batteries. Ag₂VO₂PO₄ has multiple readily accessible oxidation states (V⁵⁺, V⁴⁺, V³⁺), chemically stable polyanions (PO₄^3-), and forms of a conductive Ag network during lithiation. It represents an interesting multi-electron transfer cathode to validate recent design principles for developing higher energy density lithium-ion batteries. However, the amorphization of Ag₂VO₂PO₄ during lithiation makes the investigation of electrode reaction mechanism difficult with conventional characterization tools. To address this we have employed a combination of local probes (e.g. pair-distribution function and x-ray spectroscopy) to study its structure and chemistry as a function of electrochemical lithiation. The results were supported by sophisticated molecular dynamics (MD) simulation. We found that Ag₂VO₂PO₄ underwent a complicated electrode (discharge) reaction involving both Ag and V reduction. Initially Ag⁺ ion reduction dominates the electrode reaction with the formation of Ag metal. With the reduction progressing beyond 2.5 electron equivalents, vanadium reduction becomes dominant. Notably, the formation of Ag metal does not stop at the stage of 2 electron equivalents of reduction. This suggests the insertion of 2 Li⁺ per Ag₂VO₂PO₄ may not achieve a full reduction of residual Ag⁺ ions in Ag₂VO₂PO₄, as confirmed by in-situ/ex-situ experiments and MD simulation. This study provides in-depth understanding of the reaction mechanism for multi-electron transfer cathode materials, and will also promote the development of new generation of Li-ion batteries for biomedical applications. This research is supported by the Network of Excellence (NOE) grant from the Research Foundation of the State University of New York.

Silicon has been identified as one of the most promising candidates as anode for high performance lithium-ion batteries. The key challenge for Si anodes is the large volume change induced chemomechanical fracture and subsequent rapid capacity fading upon cyclic charge and discharge. Improving capacity retention thus critically relies on smart accommodation of the volume changes through nanoscale structural design. In this work, we report a novel fabrication method for hierarchically porous Si nanospheres (hp-SiNSs), which consist of a porous shell and a hollow core. Upon charge/discharge cycling, the hp-SiNSs accommodate the volume change through reversible inward expansion/contraction with negligible particle-level outward expansion. Our mechanics analysis revealed that such a unique volume-change accommodation mechanism is enabled by the much stiffer modulus of the lithiated layer than the unlithiated porous layer and the low flow stress of the porous structure. Such inward expansion shields the hp-SiNSs from fracture, opposite to the outward expansion in solid Si during lithiation. Lithium ion battery assembled with this new nanoporous material exhibits high capacity, high power, long cycle life and high coulombic efficiency, which is superior to the current commercial Si-based anode materials. The low cost synthesis approach reported here provides a new avenue for the rational design of hierarchically porous structures with unique materials properties.

Rechargeable batteries are potential solutions for energy storage on electric vehicles and the electric Grid. Here, we propose a bi-tortuous structured electrode (containing electrolyte-filled macro-pores embedded in micro-porous graphite) that provides a path of least resistance for Li-ion transport in the electrolyte and that by-passes transport through the thickness of the porous, graphite electrode. This enhancement in ion transport enables substantial improvement in charge/discharge capacity over conventional graphite electrodes that have microporosity alone. We recently simulated a full-cell battery (LiCoO₂ cathode/graphite anode) using a new two-dimensional version of porous-electrode theory that accounts for the anisotropic nature of ion transport in the electrolyte phase of the electrode [Nemani, Harris, and Smith, J. Electrochem. Soc., 162, A1415 (2015)]. A systematic study was conducted to explain the underlying mechanisms that determine design guidelines for such electrodes. Here, the average porosity and loading (volume fraction) of active material were held constant among all cases considered. When a macro-pore is introduced this constraint causes porosity to reduce and loading to increase locally inside the micro-porous region of the electrode. The macro-pores of width g are regularly spaced at a distance s. The principal parameters that affect the performance of a given design are (1) macro-pore coverage (defined as nu;_mp=g/s) and (2) the ratio of spacing-to-thickness (s/w). When macro-pores are frequently spaced along the electrode (low s/w) enhancement is greatest. For s/w=0.5, capacity nearly doubles that of a conventional electrode when macro-pore coverage is approximately 20%. For a 200-micron thick electrode, these conditions translate to 20-micron wide macro-pores spaced at 100 microns, revealing the fine level of microstructural control necessary to produce an enhancement in capacity with macro-pores. For electrodes with low s/w an optimum macro-pore coverage of approximately 20% maximizes discharge capacity. When macro-pore coverage increases further, micro-porosity becomes extremely small. This reduction in micro-porosity decreases effective ionic conductivity, and capacity declines as a result. We also show that a properly designed bi-tortuous electrode produces more uniform distribution of intercalated-Li through the thickness of the electrode that is expected to reduce the likelihood of Li-plating. Our future efforts aim toward fabrication of bi-tortuous electrodes, testing of their electrochemical cycling performance, and comparison with the present predictions.

Electrochemical reactions at the semiconductor-water interface, such as those encountered in aqueous corrosion and electrocatalysis are critical, rate-limiting steps that affect the performance of materials systems used for electrochemical energy generation and storage and for protection against environmental degradation [1]. The rates of these reactions and the response of the semiconductor-water interface to the surface potential depends largely on atomistic details of charge separation at the interface and the polarization of the water layers near the semiconductor surface. Therefore, the design of new electrocatalysts and corrosion resistant materials requires a thorough theoretical description of how reaction energies and barriers are affected by interfacial polarization, adsorbate solvation and electric field effects inside the electrical double layer.
In this study, we perform Density Functional Theory (DFT) calculations of adsorption energies and dissociation barriers for H₂S and H species on the charged surface of a model semiconductor, i.e. FeS₂ (100). This model system is of particular interest in the study of sulfide-induced corrosion of steels in oil field environments [2]. Further by relating the surface charge to the absolute electrode potential, we can estimate reaction energies in the ensemble of constant electric potential, which is closer to experimental conditions, compared to the constant-charge ensemble adopted in conventional DFT calculations [3].
We find that the dependence of adsorption and dissociation energies, as well as dissociation barriers depends on the extent of partial charge transfer between the electrode and the adsorbate as well as on the solvation of the adsorbate by the polarized water layers. In contrast, the strong electric fields at the interface (up to 5 MV/cm) do not significantly affect the reaction energies or barriers for molecules with compact charge distributions like H₂S and H.
References
[1] F. Osterloh, B. Parkinson, MRS Bulletin 36 (2011) 17.
[2] H. Vedage, T.A. Ramanarayanan, J.D. Mumford, S.N. Smith, Corrosion 49 (1993) 114.
[3] C. Taylor, S. Wasileski, J. Filhol, M. Neurock, Physical Review B 73 (2006).

Lithium-ion batteries have become essential components of most portable electronic devices. To improve the battery performance a tremendous research effort has been dedicated to the replacement of graphite by other materials at the anode. Tin-based systems, especially SnO and SnO₂, are very promising candidates and build the core of many research projects, receiving attention both from an experimental and theoretical point of view. Courtney and Dahn developed an empirical model to describe the lithiation of such oxides. This model is considered as the reference in the field [1]. It relies on the assumption that an amorphous Li-oxide matrix forms during the irreversible part of the lithiation, while Sn agglomerates into clusters. The reversible storage of Li is then caused by a transformation of the Sn clusters into an SnLi alloy.
Based on first-principles calculations, we propose here an alternative microscopic model to explain the reversible lithiation/delithiation of tin-oxide anodes in Li-ion batteries [2]. When the irreversible regime ends, the anode grains have been demonstrated to be ordered and consist of layers of Li-oxide separated by Sn bilayers [3]. During the following reversible lithiation, the Li-oxide undergoes two phase transformations, which give rise to i) a Li-enrichment of the oxide and ii) the formation of a SnLi composite. During the initial battery cycles the anode grain structure likely remains layered and ordered with an effective theoretical reversible capacity of 4.5 Li per SnO unit. The computed anode volume expansion and voltage profile agree well with experiments and all model structures show a high in-plane electron conductance that allows for an efficient supply of charge during operation. Furthermore, our results strongly indicate that the electrode material must remain layered to sustain its reversible capacity. The model proposed by Courtney and Dahn only accounts for the ongoing degradation of the electrode. With this knowledge we suggest that a thin-film design of the battery anodes could be a remedy for the observed capacity loss of SnO electrodes.
1 I. A. Courtney and J. R. Dahn, Journal of The Electrochemical Society 144, 2045 (1997).
2 A. Pedersen, P. A. Khomyakov, and M. Luisier, Submitted (2015)
3 A. Pedersen and M. Luisier, ACS Applied Materials & Interfaces 6, 22257 (2014).

The ability to visualize redox reactions in time and in space would enable rapid, more precise engineering of electrochemical devices such as flow batteries. Many organic molecules, such as quinones, have distinct absorbance patterns between oxidized and reduced states leading to highly visible color changes. Furthermore, many of these aromatic compounds also have unique fluorescence signatures. Using flow channels in transparent materials, we employ optical and fluorescence spectroscopy to visualize redox activity on flow battery electrodes with areas >2 cm² with <100 mu;m resolution. This technique can enable rapid optimization of flow fields and electrodes for both flow batteries and fuel cells by adding high spatial resolution of redox activity to electrochemical characterizations.

Despite the ubiquity of the Zn/MnO2 alkaline AA battery, much remains misunderstood with regards to the evolution of the electrode materials during discharge. Most methods for characterizing these materials changes are performed ex situ, and require destruction of the cell. Recent in situ methods have been useful but require expensive equipment to perform raman spectroscopy, neutron tomography, or x-ray diffraction, limiting the throughput and accessibility of such studies.
Recently, we determined the utility of in operando acoustic interrogation of batteries using Electrochemical shy;Acoustic Time-ofshy;-Flight (EAToF) analysis. The speed at which an ultrasonic pulse propagates through a battery depends on the density and modulus of the materials through which it travels. As such, the shifts in sound speed due to inherent shifts in electrode density and modulus during charge and discharge can be correlated to both the state of charge (SoC) and state of health (SoH) of a battery.
EAToF measurements were performed in transmission mode during the discharge of alkaline AA batteries from four different brands (at rates of 143 mA and 400 mA) to determine the ability of EAToF analysis to ascertain differences in their materials properties. The data from this method were compared to post mortem mass characterization data and SEM images. All brands showed higher capacity at lower discharge rates, with total discharge capacity scaling with cell price. Changes in the waveforms in the ultrasonic time-of-flight measurements were shown to correlate with the dehydration and densification of the Zn anode, with strong sensitivity to the mass loading and moisture content of each battery anode. At higher discharge rates, the formation of a ZnO crust at the anode/separator interface, which is visible in SEM images, was seen as a sudden increase in the total transmitted signal amplitude. We observed that the overall transmitted acoustic signal as well as the number of ToF echoes present at the end of discharge is dependent on the discharge rate, and correlates with anode dehydration and remaining capacity in the cell. Furthermore, by tracking the ToF position of the maximum transmitted signal, we believe it possible to track both the utilization of the anode and the expulsion of electrolyte from the anode to the cathode.

Na-ion battery has recently re-gained great interest as a low-cost alternative to current Li-ion technology. The different ionic size and reactivity of lithium and sodium in many cases affect the electrochemistry significantly. The comparison of Li and Na intercalation chemistry has been carried out extensively, with particular interest in solid state diffusion of Li+ and Na+. Because of the larger ionic radius of Na+ compared to Li+, it might be naively assumed that Na+ would always diffuse slower than Li+. However, evidence showed that Na+ diffusion can be faster than Li+ in flexible lattice frameworks such as layered oxides.
In this talk we reveal an anomalous diffusion behavior in a relatively rigid host, Na2Ti6O13. The diffusion of larger Na+ ions is 4 to 8 orders of magnitude faster than that of smaller Li+ in the open channel of Na2Ti6O13. Furthermore, we find that the diffusion of Na+ in K2Ti6O13 is slower than that in Na2Ti6O13 despite the larger tunnel in the former compound. These theoretical predictions are supported by recent findings that Na2Ti6O13 sustained quite high rate cycling (1.5 A/g) in Na cell while in Li cell its rate performance was not encouraging. By analyzing these results we suggest that the existence of a critical position where the cation-anion bonding and cation-cation repulsion simultaneously reach the maximum (or minimum) is a structural hint for fast ionic diffusion. Finally, we present several general features when using open-channel compounds as battery electrodes, and discuss the challenges and opportunities.

In the present work, in-situ stress evolution of two canonical cathode systems for rechargeable lithium ion batteries, namely layered LiCoO₂ and spinel LiMn₂O₄, in thin film configuration to quantify the driving force for mechanical degradation will be presented. Cathode thin films were prepared using sol-gel method on quartz substrates and their phase formation behavior and microstructures were characterized by XRD, Raman and SEM techniques. In-situ stress evolution in the cathode films was measured by monitoring the changes in the curvature of the elastic substrates using multiple-beam optical sensing (MOS) method in a suitably designed beaker cell during electrochemical cycling. During Li-extraction from layered Li_xCoO₂, there was an approximately linear increase in compressive stress up to ~50% Li removal, which is consistent with its lattice parameter evolution during Li removal [1]. The stress change is reversed during lithiation. The stress response is similar during subsequent cycles in which the upper cut-off voltage was limited to 4.3V, suggesting that the films undergo elastic deformation during cycling. On the other hand, initial delithiation from spinel Li_xMn₂O₄ induces tensile stress up to ~4.1V (vs. Li/Li⁺), which is consistent with the volume contraction of the material during delithiation. However, continued delithiation beyond 4.1V results in a reduction in tensile stress, which is inconsistent with reported monotonic reduction in the lattice parameter of spinel Li_xMn₂O₄ (0< x <1) during lithium extraction [2]. The subsequent lithium insertion (up to 3.5V) results in a state of compressive stress, suggesting that the final volume at the end of one cycle is greater than that at the beginning. The subsequent cycles show reversible stress cycling, with the stress becoming tensile during delithiation and compressive during lithiation, without the “stress reversal” observed during the first delithiation. The origin of the first cycle stress reversal in spinel Li_xMn₂O₄ is unknown at this point. A hypothesis, with some evidence, to explain the stress reversal in terms of oxygen loss during initial delithiation will be presented. The implications of stress measurements for mechanical degradation of cathode particles will also be discussed.
References:
[1] J. N. Reimers and J. R. Dahn, J. Electrochem. Soc.,139, 2091 (1992).
[2] Y. Xia and M. Yoshio, J. Electrochem. Soc.,143, 825 (1996).

The poor abuse tolerance of Li-ion batteries warrants complex charge management electronics, elaborate thermal management and suitable mechanical reinforcements. These would result in reduced system-level energy densities (50-60% of the cell-level values) and higher battery costs. In contrast, the aqueous systems look more appealing due to their inherent safety, even if their cell-level energy densities are marginally lower than the Li-ion systems. With this objective, we (JPL, Caltech and Liox) are developing low cost and safe (aqueous) rechargeable metal-hydride/air batteries with high energy densities (200 Wh/kg and 400 Wh/l at cell level) and long cycle life for electric vehicle applications under an ARPA-E sponsored project. Our effort is focused on developing: i) new metal hydride alloys with higher hydrogen absorption capacities, ii) stable low-cost electro-catalysts for air cathodes, iii) new cell and stack designs and iv) simpler water management schemes.
For the metal hydride anodes, the desired performance parameters include: i) High hydrogen absorption of > 1.5 w% in the gas phase with low absorption pressures (below 2 bar) and desorption temperatures (ambient), ii) High electrochemical capacity of 400 mAh/g, iii) Low corrosion rate and long cycle life (> 1000 cycles) and iv) fast electrode kinetics to operate at > C/3 rate. We initially focused on AB₅ alloys, supplied by BASF to establish the baseline for MH-air cells. Subsequently, we started developing metal hydride alloys of V-based BCC Alloys, specifically quaternary alloys of Ti-V-Ni-Cr¹, which showed discharge capacity of 400 mAh/g with 80% capacity retention over 100 cycles. Our initial studies for the bifunctional air cathode are based on thin-film noble metal catalysts, dispersed on nanostructures. Later, we developed low-cost perovskite-type catalysts for oxygen reduction and Ni-Fe-Co layered double hydroxides as catalyst for oxygen evolution. We studied the effect of electrolyte concentration on both the anode and cathode kinetics. In addition, we performed fundamental studies on the MH anodes as well as air cathodes, using the Differential Electrochemical Mass Spectroscopy (DEMS) technique, to understand the gaseous environments within a MH-air cell. In this paper, we will describe these material developments that lead to improved performance of the metal hydride-air cells.
Inoue et al., Electrochimica Acta (2012), 59, 23-3.

Despite the challenges of shape change, zinc has has been actively studied and used as an anode for 200 years. The most reducing metal that can be processed in water, zinc is low cost, earth abundant, easy to process, and air stable. It is also a two-electron material which provides a high theoretical energy density of 819 mAhr/g. Major roadblocks to its use in secondary batteries have been the formation of zinc dendrites and passivation due to ZnO formation. Even though these dendrites are traditionally detrimental to the battery performance, we have shown in previous work that when used in flooded electrolytes the local water can readily absorb heat generated by the short.
Recent work from our group shows that plating zinc at high overpotentials (-2.0 V vs. Hg/HgO) under limiting current densities produces Hyper dendritic zinc (HD-Zn), a 3-dimensional network of porous Zinc formed in highly nonequilibrium conditions exhibiting interesting properties. Once the HD-Zn is formed, it is found that cycling under “normal” operating conditions (rate < 3C) results in a more compact morphology, rather than dendritic, which makes it an excellent electrode material as no unexpected volume expansion is observed. This is in striking contrast with traditional Zn electrodes which become progressively more and more dendritic during cycling. Further, it is found that onset of passivation is delayed in HD-Zn as compared to Zn sheet. We believe this critical shift in morphology beyond the limiting current is a complex interplay of diffusion limited aggregation, surface energy differences in the facets of the hexagonal Zn crystal structure, bubble formation due to hydrogen evolution and equilibrium between Zn/ Zn(OH)₄^2-/ ZnO. Our focus is on understanding the processes by which zinc dendrites form during electrodeposition. In this work we characterize HD-Zn formation and cycling to better understand this unexpected behaviour with a variety of in-situ imaging techniques at different length scales.

Although Zinc Bromine (Zn-Br₂) secondary batteries have been studied for decades as a low cost, fully rechargeable, high density energy storage system, the large scale and widespread commercial implementation of this technology has not yet been realized due to two key limitations: i) Self-Discharge: Elemental bromine, Br₂ (l) generated during the charging cycle tends to convect and diffuse through the aqueous zinc bromide electrolyte to the Zn counter electrode, thus self-discharging the cell. ii) Zinc Dendrites: Repeated electroplating and dissolution of zinc during charging/discharging of the cell leads to the formation of dendrites, which can grow to eventually form a conductive bridge from the anode to the cathode and short-circuit the cell. [1] Zn-Br₂ flow-cells alleviate these limitations by adding bromine complexing agents and by flowing electrolyte to reduce Zn dendrite formation, respectively, albeit at the cost of cell resistance, battery efficiency, size, and capital costs. [2]
In this work, we demonstrate a simple, low-cost, non-flowing Zn-Br₂ cell design, without the use of complexing agents or separator membranes or pumps. We discuss strategies for local containment of Br₂ (l) by leveraging its unique chemistry and physical properties as well as using innovative electrode design.
The prevention of undesired Zn dendrite formation issue is addressed by using a nano-structured Zn electrode which has a more uniform growth front compared to dendritic Zn. The formation of nano-structured Zn is described elsewhere [3]. Our model test cell consists of 18 mL of 2M ZnBr₂ aqueous electrolyte which yields Coulombic efficiency of over 90% and Energy efficiencies close to 70%, with no observable fade of a 100 cycles. We record capacities of over 100mAh/g of electrolyte. This is a high capacity battery considering that this system is built for a cost << $100/kWhr. Additionally, the “self discharge” behavior of Br₂ (aq) attacking dendritic Zn front creeping towards the foam electrode is exploited for cell “self maintenance”. By removing the complexing agents, pumps and membranes from a traditional Zn-Br₂ system, we remove the majority of the cost and failure points. The cycle life of this battery is only limited by the irreversible degradation of carbon. In this work, we successfully combine a new cell design with a new non-invasive optical technique of measuring fundamental aspects of cell level transport conditions in real time.
References:
[1] P.C. Butler et al. Handbook of Batteries,Ed. 3, Ch. 39, McGraw-Hill, Ohio (2001)
[2] D. Ayme-Perrot et al., J. Power Sources (2008) 175, 644
[3] M. Chamoun et al., NPG Asia Materials (2015) 7, e178

Non-aqueous redox flow batteries (NRFB) offer an attractive alternative to aqueous redox flow batteries due to a broad materials design space and wide electrochemical windows. Additionally, a recent techno-economic study shows that NRFB&’s open a new pathway towards achieving economically viable grid-level energy storage [1]. A number of studies report on the electrochemical properties of electroactive compounds in non-aqueous electrolytes (i.e. Brushett et al. [2], Escalante-Garcia et al. [3], etc.). Nearly all of these redox chemistries, however, are tested only in beaker cells or un-optimized flow cells. Hence, designing high-performance non-aqueous flow cells tailored for different chemistries becomes a paramount challenge given the breadth of available chemistries and lack of materials properties (i.e. viscosity, conductivity, etc.) knowledge required for cell design.
To tackle this design problem, a mixed experimental-modeling approach is underway. First, experimental efforts identify an entry cell design and materials set. Specifically, a high-performance vanadium redox flow cell [4] serves as the initial architecture, employing typical Li-ion battery solvents (i.e. PC/EC, EC/DMC, etc.). Polarization and impedance measurements are collected in a single-electrolyte study [4] to verify the impact of cell design, electrolyte selection, and flow rate on cell performance for model active compounds (i.e., TEMPO [5]). Various commercially available separators are also investigated. Second, transport and electrochemical modeling optimizes NRFB performance as a function of electrolyte, active compound, and electrode properties as well as cell geometry. Importantly, this modeling effort identifies dimensionless variables from which we develop chemistry-agnostic design rules for NRFB&’s. Ultimately, single-electrolyte experiments will be used to verify the performance trends identified via the transport-electrochemical modeling, creating a tool for predicting optimized cell designs given a set of input materials properties.
Acknowledgments
We acknowledge the financial support of the Joint Center for Energy Storage Research and the National Science Foundation Graduate Research Fellowship Program.
References
[1] R.M. Darling et al., Energy Environ. Sci. 7 (2014) 3459-3477.
[2] F.R. Brushett et al., Adv. Energy Mater. 2 (2012) 1390-1396.
[3] I.L. Escalante-García et al., J. Electrochem. Soc. 162 (2015) A363-A372.
[4] R.M. Darling and M.L. Perry, J. Electrochem. Soc. 161 (2014) A1381-A1387.
[5] X. Wei et al., Adv. Mater. 26 (2014) 7649-7653.

As an emerging battery technology, Li-redox flow batteries inherit the advantageous features of modular design of conventional redox flow batteries and high voltage and energy efficiency of Liminus;ion batteries, and show promise as efficient electrical energy storage system in transportation and residential applications. The chemistry of lithium redox flow batteries with aqueous or non-aqueous electrolyte potentially provides widened electrochemical potential window thus may provide much greater energy density and efficiency than conventional redox flow batteries based on proton chemistry. This talk will discuss recent advances, and some critical challenges/opportunities with this new battery system.

Quinone-based flow batteries are attractive candidates for large-scale electrical energy storage, as quinones can be inexpensive, exhibit rapid redox kinetics, and require no electrocatalyst [1-3]. We present the evaluation of several quinone negative electrolyte materials for use in a flow battery with a positive electrolyte containing bromine and hydrobromic acid. Several substituted quinones are shown to undergo reversible two-electron reduction and oxidation in acidic aqueous solution, with tunable reduction potentials. Some are found to be stable in the presence of bromine, while others undergo decomposition reactions. One stable substituted quinone is currently being tested in a quinone-bromide flow battery. The cell exhibits a peak galvanic power density above 700 mW/cm², an average round-trip energy efficiency of over 70%, and a current efficiency of over 95% as tested to 25 constant-current charge-discharge cycles at 0.25 A/cm². Additionally, sulfonation of anthraquinone is shown to produce a suitable negative electrolyte through a simple, scalable chemical process using inexpensive starting materials. This negative electrolyte is shown to have similar performance to research-grade commercially available quinones.
[1] B. Huskinson, M.P. Marshak, C. Suh, S. Er, M.R. Gerhardt, C.J. Galvin, X. Chen, A. Aspuru-Guzik, R.G. Gordon and M.J. Aziz, “A metal-free organic-inorganic aqueous flow battery”, Nature505, 195 (2014), http://dx.doi.org/10.1038/nature12909
[2] B. Huskinson, M.P. Marshak, M.R. Gerhardt and M.J. Aziz, “Cycling of a quinone-bromide flow battery for large-scale electrochemical energy storage”, ECS Trans.61, 27 (2014)
[3] B. Yang, L. Hoober-Burkhardt, F. Wang, G.K. Surya Prakash, and S.R. Narayanan, J. Electrochem. Soc.161, A1371 (2014).

Vanadium redox flow batteries (VRFBs) are an emerging electrochemical technology that offers unique advantages for grid-scale energy storage due to their flexible design and decoupled power/energy feature [1]. However, the high capital cost of VRFBs due to their expensive vanadium-based electrolyte and need for durable ion exchange membranes hinders widespread implementation and commercialization of these systems [2]. As a result, we are investigating cost effective redox flow batteries using less toxic, widely abundant and less expensive active materials such as iron and copper [3]. However, unlike the vanadium-based system, both iron and copper chemistries require the use of an electrochemical plating reaction, which recouples energy and power ratings. In order to mitigate this issue, instead of using a conventional, stationary electrode, a novel flowable slurry electrode strategy is implemented. The details of the system operation along with the current technical challenges are discussed using both all-iron and all-copper chemistries. Finally, the performance characteristics of these systems obtained from cyclic voltammetry, electrochemical impedance spectroscopy and battery cycling analyses are reported.
References:
[1] A. Z. Weber, M. M. Mench, J. P. Meyers, P. N. Ross, J. T. Gostick, Q. Liu, J. Appl. Electrochem., 41, 1137-1164 (2011).
[2] R. M. Darling, K. G. Galagher, J. A. Kowalsky, S. Ha, F. R. Brushett, Energy Environ. Sci., 7, 3459-3477 (2014).
[3] T. Petek, N. C. Hoyt, J. S Wainright, R. F. Savinell, J. Electrochem. Soc., 161 (1), A5001-A5009 (2016).

Redox flow batteries (RFBs) are of broad interest for large-scale energy storage. They exhibit high stability due to the lack of phase change upon cycling, and several RFB chemistries also exhibit very high thermal stability. However, additional work is needed to address the issues of system complexity and irreversible capacity losses that continue to inhibit the implementation of RFBs. We have undertaken detailed analysis on the concept of the symmetric redox flow battery, or SRFB, which relies on a single parent molecule as the charge storage species in both the positive and negative electrode reactions. Here we present models outlining the benefits of using one electrolyte as both the anolyte and catholyte. These models are further supported with experimental studies and demonstration devices using substituted diaminoanthraquinones (DAAQs) as promising candidates for use in SRFB redox electrolytes.