Exploration and development of new and renewable energy like solar and wind energy are one of hottest topics of our times. However, for renewable energy to be competitive with coal, natural gas, nuclear, and oil, it needs to be cost effective and reliable. Energy storage especially large scale energy storage is the key technology to achieving this. As one kind of energy storage technique, the vanadium flow battery (VFB) was well-suited for relatively large-scale utility applications due to its attractive features like long life, active thermal management and independence of energy and power ratings. Numerous application demonstrations indicated that VFB can meet the demands of large-scale energy storage and is suitable for the applications like renewable energy generation and the distributed energy supply etc. However, the relatively low power density of VFB leads to its too high cost and further hinders its further commercialization. Therefore the current efforts were mostly focus on lowering the VFB cost by exploring key materials with improved performance. Dalian Institute of Chemical and Physics (DICP) has devoted to VFB research for more than 10 years from materials to system integration. where a spin-off company (Rongke power Co.Ltd) was established in 2008, and the demonstrations of VFB in different application field were carried out, including the world largest 5MW/10MWh VFB system installed in 2013. The key materials including electrolytes, electrodes and membranes were successfully explored and realized mass production via investigating the structure-performance relation of the materials. For the electrolytes, the transfer behavior of electrolytes were clarified via investigating the transfer behavior in membranes with different morphologies, the results showed the capacity decay rate of VFB could be lowered via changing membranes materials. For the bipolar plates, the concept of carbon composite bipolar plate was proposed and the batched preparation techniques were explored, where the production capacity has reached 20,000 m2/year. Meanwhile, porous membrane separator was first introduced into VFB based on the idea of separating vanadium ions from proton via pore size exclusion. This new concept successfully overcomes the restriction caused by ion exchange groups from traditional ion exchange membranes, which broadens the materials option of VFB membranes. In this presentation, the research on VFB key materials will be introduced and the progress of key materials in DICP will be presented. References: 1. Cong Ding, Huamin Zhang, Xianfeng Li, Tao Liu, and Feng Xing, J. Phys. Chem. Lett., 2013, 4 (8), pp 1281-1294 2. Hongzhang Zhang, Huamin Zhang, Xianfeng Li, Zhensheng Mai, Jianlu Zhang, Energy & Environmental Science 2011, 4 (5), 1676 - 1679

Quinones can undergo rapid two-electron two-proton reduction to hydroquinone in acid, making them interesting candidates for large-scale energy storage applications. Functional groups can be appended to tune the solubility and reduction potential, enabling relatively large energy densities. Anthraquinone-2,7-disulfonic acid was paired with the bromine-bromide redox couple to construct a flow battery in which we observed power densities exceeding 125 mW/cm² at 80% round-trip energy efficiency (> 600 mW/cm² peak power) and coulombic efficiencies over 95%. The performance of quinone flow batteries has recently been improved to have higher voltage by chemically modifying the quinone. In addition, a new catalog of stable redox-active organic materials that exhibit both low and high reduction potentials will be presented, enabling flow batteries composed entirely of organic materials.

In a recent publication¹, we showed that the incorporation of earth-abundant organic molecules, such as quinones, into aqueous flow batteries offers various advantages over current flow battery technologies. These advantages include scalability, kinetics, stability, solubility, and tunability. With the opportunity to use quinones for grid scale energy storage, the new objective is to find the best performing molecules that would meet the required properties and functionalities of a practical flow battery. In this presentation, we will introduce a large-scale computational study that is designed to explore new quinone-based energy storage materials. Specifically, we will show a high-throughput computational methodology that is capable of screening the redox behaviors of quinones in an accelerated way. The theoretically predicted redox properties of 10,000+ quinone/hydroquinone molecules, which were generated with the functionalization of various quinone backbones with 18 distinct functional side groups, will be presented.
1. Huskinson, B. et al. A metal-free organic-inorganic aqueous flow battery. Nature 505, 195-198 (2014).

Energy storage systems are crucial for extensive fraction of intermittent renewable energy such as solar and wind systems and huge demand on the electrical grid to recharge electric vehicles. Scalable energy storage with low cost and high energy density will be a key to meet these challenges. Lithium-polysulfide (Li-PS) batteries are attractive due to their high theoretical energy density, and reasonable kinetics for grid storage applications.
Here-in, we present a materials-to-system analysis of the Li-PS hybrid flow battery for grid storage applications. We investigate the correlation between technological performance and system cost by using modified Batpac.
In the system, lithium polysulfide in ether-based solvent and metallic lithium is used as the catholyte and anode, respectively. The system price of a flow battery system is allocated into the cost of reactor, catholyte, catholyte storage vessel, balance-of-plant components.
Here we show the consequences on cost from change in system properties such as redox material concentration, specific capacity, and material cost to derive the requirements and challenges for the system to achieve $100/kWh.
Although limited solubility of lithium polysulfide and electrolyte cost are challenging constraints, Li-PS hybrid flow battery is found to be a promising technology for grid storage owing to their scalability and potentially low cost.

Development of renewable energies such as solar and wind power have received a great deal of attention. However, in order to utilise efficiently the power generated, it is essential to introduce energy storage systems at the grid level scale. Redox flow batteries are excellent candidates for this purpose as they present many potential advantages such as: decoupling of power and energy; modularity (kilowatts to megawatts systems); site independence; long cycle life; and minimal maintenance.
But there remains scope to reduce the cost and improve the performance of current systems, and in this context a novel regenerative fuel cell, utilising an aqueous vanadium electrolyte and hydrogen gas has recently been reported¹. The advantages offered by this approach are fast hydrogen kinetics, use of half of vanadium electrolyte in comparison to the conventional all vanadium flow battery and the absence of cross-contamination between the positive and negative half-cells.
The first generation of this vanadium-hydrogen cell assembled with commercial MEAs demonstrated a maximum power density of 107 mW/cm² in a 1M V(IV)/V(V) solution. In this work we report improved performance to achieve a maximum power density of 229 mW/cm² through cell design modification. Half-cell measurements have been used to gain a better understanding of the loss mechanisms in the cathode and anode. Additionally, the authors have implemented the use of 3D tomography to study the structural changes of carbon based electrodes over different numbers of experimental conditions. The latest results from these studies will be presented.
¹ V. Yufit, B. Hale, M. Matian, P. Mazur and N.P. Brandon, Development of a Regenerative Hydrogen-Vanadium Fuel Cell for energy storage applications, Journal of The Electrochemical Society, 160 (2013), A856-A861.

Public and private investments in energy storage have created a 100 billion dollar industry, and this industry is now converging on grid-scale applications due to the urgent need for resource conservation and #8232;our ever-increasing global demand for energy. Redox flow batteries (RFBs) are an emerging method for grid-scale energy storage, being used for peak-shaving and renewable energy incorporation into the grid. Current state-of-the-art RFB electrolytes are composed of aqueous mixtures of metals that compete on cost and simplicity, but narrow electrochemical windows and low energy density are detriments to fully exploiting the RFB architecture.
Our laboratory set out to develop the next generation of RFB electrolytes with targets of single-potential, multi-electron redox events with greater than 2 V operating potentials. To achieve this goal, we have exploited the biomimetic property of redox non-innocence, which allows the metal and peripheral ligands of a complex to store equivalents of electrons separately without perturbing the central metal atom's chemical bonds. The responsibility for redox events is no longer shouldered only by the central metal atom, and is instead, shared by the components of the complex. Because ligands can operate independently, they can also act simultaneously yielding engineered multielectron redox events. This advancement will double or triple energy density and engineer stability (and cyclability) into the molecular design.
This talk will highlight the recent results of electrolyte development based on transition metal and main group element complexes and our new Raman-based spectroelectrochemical analysis.

Flowable suspensions that conduct both electrons and ions can enable the use of energy-dense electroactive species (e.g., Li-ion-storage compounds and solution/precipitation chemistries) in flow batteries (FBs). This class of FBs shows unique properties that must be considered to engineer devices: (1) electrochemical reactions can take place outside the cell&’s stack when the suspension has mixed conductivity; (2) shunt currents can arise from both electronic and ionic conductivity; and (3) suspensions have flow resistance due to non-Newtonian rheology. Here, we quantify the impact of these processes on FB energy efficiency, and identify the design, operational, and materials parameters by which they can be controlled.
Typically the electroactive zone (EAZ) in which electrochemical reactions occur extends beyond the stack&’s current collectors (the extension being termed the side zone, SZ), because ions and electrons can conduct out of the stack when suspensions are used. Electrochemical reactions in SZs are generally inefficient and can reduce the energy efficiency of the FB. The added inefficiency can be avoided in practice by extending current-collector length. We show that SZs contribute less than 1% additional energy inefficiency at C/10 rates for current collectors greater than 20 mm long for typical nonaqueous suspensions.
FBs have shunt currents between electrodes arranged in multilayer stacks due to the electrical connectivity of shared fluid pathways. Ionic and electronic shunt currents occur in parallel in mixed-conducting suspensions, and the net current is proportional to total conductivity (i.e., the sum of ionic and electronic conductivity). Scaling analysis shows that based on total conductivity, nonaqueous lithium-polysulfide suspensions should have only 1/25^th the shunt losses of aqueous flow batteries. In the case of a lithium-polysulfide solution containing 1 vol. % Ketjen black, the resulting mixed-conductor has equal ionic and electronic conductivity of approximately 2 mS/cm. Such a mixed conductor with equal electronic and ionic transference number is ideal for FBs, because low cell impedance and minimal shunt currents are realized simultaneously.
Mixed-conducting suspensions exhibit shear-thinning rheology for which viscosity decreases monotonically with shear rate. At high shear rates, the above mentioned lithium-polysulfide suspensions has a viscosity (~700 mPa-s) that is nearly one-hundred fold higher than the solution counterpart (~20 mPa-s). However, the suspension-based FB does not require use of a porous current collector. Thus, the mechanical loss upon pumping the high viscosity suspension through an unobstructed flow channel (e.g., ~1mm thick) is ~1000 times smaller than that to pump the solution through a carbon felt current collector with ~10mu;m pores. In addition, the suspensions can reduce their flow-resistance through wall slip, which further increases the electrochemical efficiency of FBs.

Flow batteries have the potential to provide low-cost energy storage to enable widespread integration of renewable energy sources (e.g., solar and wind) into the power grid. Current flow battery architectures are typically mechanically complex, due to the need for simultaneous control of flow and electrochemistry. Towards the development of simpler, robust, passively driven, lower-cost flow battery architectures, here we demonstrate a prototype of one particular design concept, a Gravity Induced Flow Cell (GIFCell). The flow electrode used is an electronically conductive lithium polysulfide suspension that incorporates a percolating network of nanoscale carbon.¹ Lithium metal is used as the anode, thereby forming a semi-flow cell. A key challenge in this design is achieving uniform flow with non-Newtonian fluids. In particular, higher loadings of carbon (>0.75 vol%) in the suspension that are desirable for increasing electronic conductivity and discharge power also significantly increase the yield stress of the suspension, resulting in flow instabilities due to viscous fingering and contact line pinning. Strategies for introducing high slip surfaces into the GIFCell structure were developed that enable uniform flow. The results presented will illustrate the integration of flow electrode electrochemical design, cell mechanical design, surface engineering, and electrochemical testing.
Acknowledgement
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, O#64259;ce of Science, Basic Energy Sciences.
Reference
¹F.Y. Fan, W.H. Woodford, Z. Li, N. Baram. K.C. Smith, A. Helal, G.H. McKinley, W.C. Carter, Y.-M. Chiang, “Polysulfide Flow Batteries Enabled by Percolating Nanoscale Conductor Networks,” Nano Letters, 2014, 14 (4), pp 2210-2218

Recently there has been a renaissance of new flow-assisted electrochemical devices for grid energy storage. Among these new technologies is a new family of flow systems that rely on flowable suspensions for charge storage. Unlike traditional flow-batteries which utilize insulating redox-electrolytes, suspension electrodes (flowable electrodes) rely on percolation networks of contacting active materials to facilitate charge storage. Capacitive suspension electrodes (CSEs) are one type of flowable electrode that typically utilize a porous active materials, and store charge electrostatically in an electric double layer. Unlike traditional supercapacitors, the flowing nature of this system offers the ability for continuous and scalable charge storage. Although the suspension-type electrodes exhibit high power density, they are limited in terms of their energy density. In order to compete with existing applications for grid level energy storage or desalination the energy density of the suspension electrode needs to be improved.
In this study we highlight the key material aspects toward the design of high performing flowable electrodes considering energy density, power density, and rheological properties. From a materials viewpoint, it is important to understand how the active material&’s surface heteroatoms effects the electrochemical, kinetic, and rheological performance of flowable electrodes. Surface functionalization has been widely studied in the electrochemical capacitor literature as a means for achieving pseudocapactive charge storage, however in a suspension electrode the surface functional groups will play a role in how active materials interact (and flow) as percolation networks. Thus, in this study the combined pseudocapacitive and rheological properties of CSEs based on activated carbon enriched with oxygen heteroatoms was examined. CSEs composed of oxidized carbon achieved a higher mass loading (~140x greater) than suspension electrodes based on unoxidized activated carbon. Furthermore, it was observed that the high mass loaded suspension electrodes (28% carbon content) based on oxidized activated carbon displayed similar viscosities to low mass-loaded (20 % carbon content) suspension electrodes based on as-received carbon. Finally, we present how CSEs can be used in dual systems for desalination and energy recovery.

Thermal batteries are generally used as main power sources for many military applications, such as missiles and ordnance due to their excellent robustness, reliability, and long shelf-life. Lithium alloy(Li(Si)) and pyrite(FeS₂) are primarily used as anode and cathode materials in thermal batteries, respectively. However, FeS₂ cathodes have a high internal resistance which reduces the electrochemical performance of Li(Si)/FeS₂ thermal batteries. In order to reduce the internal resistance by forming conductive network structures between the pyrite particles. We investigated electrochemical behaviors of the FeS₂ cathode by adding carbonblacks(CBs) or multi-walled carbon nanotubes(MWCNTs) with various amounts from 0.1 to 1.0 wt.%. The internal resistance of the FeS₂ cathodes was reduced, and the electrochemical performance of thermal batteries could be improved by the addition of conductive carbonaceous materials to FeS₂ cathodes.

We demonstrate a route to integrate active material for energy storage directly into a silicon photovoltaic (PV) device, and the synergistic operation of the PV and storage systems for load leveling. Porous silicon supercapacitors with 84% Coulombic efficiency are etched directly into the excess absorbing layer material in a commercially available polycrystalline silicon PV device and coupled with solid-state polymer electrolytes. Our work demonstrates the simple idea both that the PV device can charge the supercapacitor under an external load and that a constant current load can be maintained through periods of intermittent illumination, demonstrating the concept of an all-silicon integrated solar supercapacitor.

Rechargeable Lithium-air batteries have been researched for last several years because of its high theoretical energy density such as 10⁴ Whkg^-1 [1]. And many researchers have reported much higher practical energy density (over 4000mAhg^-1) of lithium-air batteries than practical energy density of lithium-ion batteries (~360 mAhg^-1). In addition, development of diverse effective organic-based electrolyte leads to realize good cycleability. However, using liquid type organic electrolyte has many problems such as evaporation, contamination by water from the ambient air, leakage, safety hazard and flammability [2].
Applying gel polymer electrolyte as solid type can be one strategy to solve the problems mentioned above. The poly vinylidene fluoride (PVDF) has good property to be used for solid electrolyte matrix such as high dielectric constant to dissolve the lithium salts, thermal stability and good mechanical property [3]. So that, some researches using PVDF electrolyte matrix for solid type electrolyte has been reported in battery society [3, 4]. However, in case of lithium-air batteries, the contact of interface between cathode and electrolyte is significant to drive chemical reaction due to the volume change of air cathode part by formation of lithium peroxides.
In this work, we synthesize the morphology changeable PVDF matrix solid type electrolyte with LiPF6, and characterize its mechanical and electrical characteristics. The electrolyte is synthesized using electro-spun technology and the polymer chain reaction control skill. In the middle layer of membrane, the textile structure composed of PVDF micro fibers leads to good mechanical property and it functions as separator. The soft electrolyte part as interface contacting with electrodes is synthesized by addition of benzoquinone as inhibitor to stop chain reaction of PVDF. We demonstrate that the ionic conductivity is up to 3 x 10^-3 SCm^-1 by calculating of impedance analysis. Also, the synthesized electrolyte shows good charge-discharge cycle characteristics.
Acknowledgment
This research was supported by the MSIP(Ministry of Science, ICT and Future Planning), Korea, under the “IT Consilience Creative Program” (NIPA-2014-H0201-14-1002) supervised by the NIPA(National IT Industry Promotion Agency)
[1] K. M. Abraham and Z. Jiang, J. Electrochem. Soc. 143 (1996)1.
[2] J. Christensen, P. Albertus, R. S. Sanchez-Carrera. T. Lohmann, B. Kozinsky, R. Liedtke, J. Ahmed and A. Kojic, J. Electrochem. Soc. R1 (2012) 159
[3] Y. Zhu, S. Xiao, Y. Shi, Y. Yang, Y. Hou and Y. Wu, Adv. Energy. Mater. 4 (2014) 1300647
[4] P. Yang, L. Liu, L. Li, J. Hou, Y. P. Xu, X. Ren, Electrochimica Acta 115 (2014) 454

Ultracapacitors, also known as supercapacitors, have the potential to meet the high pulse power capability related to the power quality and grid instability for grid-scale energy storage applications. Ultracapacitors can accept the electric power surges generated from renewable energy sources and deliver the surges of electric power in burst mode to the grid. It is important to calculate accurately the electrical and thermal behaviors of an ultracapacitor for the efficient and reliable systems integration from an application perspective. In this work, modeling is performed to study the electrical and thermal behaviors of a 2.7V/3000F ultracapacitor from LS Mtron Ltd. A three-branch circuit model is employed to calculate the electrical behavior of the ultracapacitor. To predict the thermal behavior of the ultracapacitor, Joule-heat and reversible heat at the electrodes are consdered. The validation of the modeling approach is provided through the comparison of the modeling results with the experimental measurements.

With the huge commercial success of Tesla as an electric model, the important role and great need of electrochemical storage and batteries specifically will continue. Here we demonstrate a high energy density flow storage system at an eco-friendly mode, the Ni/Zn flow battery system (NZFBS), which combines the advantages of conventional batteries and fuel cells designed for high power and high capacity electricity storage application. Unlike Lithium-ion battery or redox flow battery, the success of this brand new flow battery utilizes an electronic-ionic conductive suspension with Ni/Zn chemistry, and it can provide a new solution for the energy storage with high energy density (200 Wh/L), high power density (100 mW/cm²), low cost ($100/kWh), long cycle life (5000 cycles) and high safety. It meets the growing safety demand from customers and relieves the mounting serious environmental issue, and provides a rapid charging option for electric vehicle industry. The characteristics of component optimization during Charge/Transport/Discharge through simple processing techniques, such as Concentration/Dilution, enables NZFBS a better commercial application potential and a concept of gasoline-like “NZFBS station”. This study demonstrates the prototype of NZFBS, electrochemical performance data under both half-cell and full-cell conditions, and the proposed applications on electric vehicles and large scale grid storage.

Lithium-sulfur (Li-S) batteries have attracted significant attention as one of the most promising of the next-generation lithium rechargeable batteries due to its high theoretical capacity (1,675 mA h g^-1), high energy density (~2,500 W h kg^-1), low cost and environmental friendliness. However, two challenges have remained major obstacles for the commercialization of Li-S batteries. First, low power capability is often observed due to the insulating nature of sulfur and its reduction products (Li₂S₂, Li₂S). Second, fast capacity fading characteristics, which originate from the generation of various soluble polysulfide Li₂S_x (3 le; x le; 8) intermediates, result in poor cycle life. In Li-S batteries, dissolved polysulfides transport through the electrolyte and dissipate the lithium ions and electrons at the anode side via direct chemical reactions, a phenomenon called the ‘shuttle effect&’.
In order to improve the cycling performance of Li-S cells, in this work, we propose a unique hierarchical structure interlayer composed of glass filter/carbon nanotube composite (GF/CNT) paper, which can offer high electrolyte wettability and superior electronic conductivity for the reactivation of dissolved polysulfides in Li-S cells. The GF/CNT paper, which serves as a polysulfide diffusion inhibitor, is assembled between the sulfur cathode and the separator and not only significantly reduces the charge transfer resistance of sulfur cathodes, but also localizes and retains the dissolved polysulfides. This leads to much enhanced electrochemical reactions at the cathode side during cycling.
The Li-S cells with the GF/CNT paper interlayer deliver a higher initial capacity of 1111.7 mA h g^-1 at 1.5-2.8 V at a rate of C/5 compared to the cells with an interlayer of glass filter paper alone, or without any interlayer, and the capacity remains 841.78 mA h g^-1 after 200 cycles. The improved cell performance is attributed to outstanding electrolyte uptake property of the glass filter, and the high electronic conductivity of carbon nanotube, serving as a conductive porous backbone for trapping and depositing the dissolved polysulfides. The combination of highly porous glass filter with conductive carbon nanotube presents a low-cost approach to overcome the persistent problems of lithium-sulfur batteries.

Li(Si)/FeS₂ system is the most popular couple for thermal batteries used for primarily power sources for guided missiles and proximity fuzes in ordnance devices to provide power for radar and electronic guidance as well as guidance-fin motors. However, large particles and impurities of pyrite (FeS₂) limit its use in high power applications because of its low specific area and usage of active material. In this study, we fabricated nanoscale cathode powders using a high energy milling technique to obtain high specific area of FeS₂ powder by changing ball to power weight (BPR), milling speed (RPM) and time. In addition, we evaluated the discharge performances of single cells fabricated with the powders. Discharge performance of the single cell with thermally annealed FeS₂ powders at 400#8451; was greatly improved compared with the FeS₂ powders not annealed.

The lithium-ion battery (LIB) is one of the preferred candidates for grid-scale energy storage systems due to its outstanding characteristics such as high energy density, modular scalability, long cycle life, and low self-discharge rate among others. In a battery module for grid-scale energy storage applications, an uneven temperature distribution in the module can be created depending on the operating conditions and the types of thermal management. Uneven temperature distribution in a module could cause an electrical imbalance and thus lead to the lower performance and shorter life of battery. It is, therefore, important to calculate accurately the uneven temperature distribution in a battery module in order to achieve the optimum performance and long life of the battery module. In this work, a modeling is performed to investigate the effects of operating conditions on the thermal behavior of an LIB module. Thermal conductivities of various compartments of the battery are estimated based on the equivalent network of parallel/series thermal resistances of battery components. Heat generation rate in an LIB cell is calculated by using the modeling results of the potential and current density distributions of a battery cell. The temperature distributions in the LIB module obtained from the modeling are in good agreement with the experimental IR images.

A conventional zinc-air cell (ZAC) does not exhibit high voltage and its
performance can be affected by the CO₂ due to CO₂ contamination on the cathode.
In this study, we present a novel design of tri-electrolyte zinc air cell (TZAC)
and compare it with the conventional counterpart. Based on this new design, the
open circuit voltage (V_oc) has been improved from 1.5 V to 2.0 V. Moreover, the
power density has also been enhanced by around 44%. In suit anodic and cathodic
potentials investigation suggests that in the low current density region, the activation
polarization by oxygen reduction reaction (ORR) is more dominant in TZAC
than in ZAC, while in the high current density region, the reverse is true. This
observation is also confirmed with the electrochemical impedance spectroscopy (EIS)
measurements. In addition, EIS results suggest that the internal resistance of TZAC
is slightly higher due to the use of membranes and extra electrolyte. Overall, TZAC
exhibit much better performance and may be one of the promising candidates for
large-scale application.

Recently, although we and other groups have pointed out the feasibility of using MoO₃ or MoO_3-x as a negative electrode in SCs, few studies have focused on capacitive behavior of MoO₃ due to its naturally poor conductivity and rate capability especially at high mass loading levels. In this work, hydrogenation method is applied to promote the conductivity of MoO₃ which is demonstated by both of first principle calculation and single nanobelt measurement. Freestanding hydrogenated MoO₃ (MoO_3-x)/CNT electrodes (mass density 2.5 mg/cm²) were fabricated and showed much improved electrochemical performance, such as a specific capacitance of 337.5 F/g (based on the mass of MoO_3-x) and a high volumetric capacitance of 291.4 F/cm³ (based on the whole electrode) with 64% initial capacitance at 10A/g (unaware of such values in other oxide). Also we confirmed the improved intercalation kinetics and the increased intercalation pseudocapacitance could be attributed to the higher electronic conductivity of MoO_3-x, which results in better and faster intercalations of the Li ions. This electrochemical behavior implied that MoO_3-x could be a very good negative electrode with high capacitance at high mass loading levels.
Acknowledgement
This work was financially supported by the National Natural Science Foundation of China (51322210), a Foundation for the Author of National Excellent Doctoral Dissertation of PR China (201035).

The seemingly ubiquitous Li-ion batteries exhibit superb performance as compared to other types of rechargeable batteries. However, among light metals, Li is a very rare element, which requires active search for suitable alternatives. Among these, Na- and Ca-ion batteries have drawn significant attention in recent years. However, many of the anode materials being pursued have limitations including volume expansion, lack of passivating films and slow kinetics. Here, we investigate graphene with divacancy and Stone-Wales defects as a possible high-capacity anode material for Li-, Na- and Ca-ion batteries. Our results show that while adsorption of adatoms is not possible on pristine graphene, enhanced adsorption is observed on defective graphene due to increased charge transfer between the adatoms and defects. We find that the capacity of batteries increases with the density of defects. For maximum possible divacancy defect densities, the capacities of 1600 mAh/g, 1450 mAh/ and 2900 mAh/g for Li-ion, Na-ion and Ca-ion batteries respectively can be achieved. While for Stone-Wales defects, we find maximum capacities of 1000 mAh/g, 1071 mAh/g and 2142 mAh/g respectively. Our results provide guidelines to create better high-capacity anode material for Li-, Na- and Ca-ion batteries.

Lithium-ion batteries (LIBs) have achieved great success as energy storage and conversion systems in the past two decades. However, Due to the limited and globally uneven distribution of lithium resources, it is expected that the cost of the LIBs will dramatically increase in the near future.¹ Therefore, exploiting novel low-cost energy storage devices with naturally abundant raw materials will soon be required. Ambient temperature sodium-ion batteries (SIBs) are promising candidates and have attracted increasing attention due to the abundance of sodium sources.¹ Unfortunately, the graphite anode commonly used in lithium systems does not intercalate sodium to any appreciable extent, as the Na ions have a much larger radius of 1.02 Å (~55% larger than the Li ion radius of 0.76Å). This is a serious hurdle for practical application of SIBs, and necessitates design of new anode materials to allow reversible and rapid Na ion insertion and extraction.
Recently, phosphorus was found to be electrochemically active for sodium ions with an extremely high theoretical capacity of 2595 mAh/g, the highest among known anode materials for SIBs. Though very promising, this battery performance is still unsatisfactory, particularly with regards to the cycling stability. There are several likely reasons for this. First, red phosphorus has a very low electrical conductivity (1×10^-14 S/cm), making the electrochemical redox reaction difficult. Second, similar to silicon in LIBs, the large volume expansions of phosphorous (>300%) may cause many problems for phosphorus anodes. In particular, the cyclical large volume change is expected to cause poor electrical contact between phosphorus particles and the conducting matrix, pulverization of phosphorus particles, and continuous growth of the solid electrolyte interphase (SEI). As a result, phosphorus anodes show fast capacity fading, low Coulombic efficiency, and electrode deterioration upon cycling.
In this talk, we will present a novel graphene nanosheets-wrapped phosphorus (P/G) composite anode for sodium-ion batteries through facile ball-milling method. The large surface and flexibility of graphene enable it to wrap around phosphorus particles, enhancing the overall conductivity and acting as a flexible buffer layer to stabilize the SEI of phosphorus during cycling. Benefiting from this unique structure, the as-synthesized P/G composite shows much improved electrochemical performance with a high initial capacity of 2077 mAh/g and good cycling stability (80% capacity retention after 60 cycles). The low-cost, eco-friendly starting materials of red phosphorous and graphene stacks together with the industry-standard ball-milling approach make this anode material promising for the practical application in sodium-ion batteries.
1.M. D. Slater, D. Kim, E. Lee and C. S. Johnson, Adv. Funct. Mater., 2013, 23, 947.
2.J. Qian, X. Wu, Y. Cao, X. Ai and H. Yang, Angew. Chem. Int. Ed. Engl., 2013, 52, 4633.

X-ray Compton scattering is one of the non-destructive techniques to measure Li concentration in battery materials since the line-shape of Compton scattered X-rays or the so-called Compton profile is sensitive to the chemical composition of a target material. An advantage of this technique is its applicability to a large battery since X-ray Compton scattering uses high energy X-rays over 100 keV, which can penetrate deep in the bulk of the material. In this study, we have applied this technique to Li_xMn₂O₄ and we have shown the newly proposed, line-shape and S-parameter analysis to determine the Li concentration in large batteries.
The Compton scattering experiment was carried out at the BL08W beamline of SPring-8, Japan. The incident X-ray energy was 115keV and the scattering angle was 165 degrees. The measurements were performed in vacuum and at room temperature. Polycrystalline Li_xMn₂O₄ (x=0.5, 1.1, 1.2, 1.8, 2.0, 2.1 and 3.3) samples were prepared by controlling the Li composition chemically.
Compton profiles obtained from Li_xMn₂O₄ are sensitive to the Li composition in the low momentum region. In order to evaluate Li concentration from the experimental data, we introduce a parameter S, which is defined as a ratio of the central area to the tail area in the Compton profile. The experimental S-parameters of Li_xMn₂O₄ are found to depend linearly on the Li concentration measured with the inductively coupled plasma (ICP) technique. In addition, we have calculated theoretical S-parameters by using Hartree-Fock and KKR-CPA methods. The theoretical S-parameters reproduce the x dependency of the experimental ones, supporting our experimental finding that the S-parameters are proportional to the Li concentration. This property implies that the Li concentration of Li_xMn₂O₄ with unknown x can be deduced from the S-parameter. The line-shape and the S-parameter of Compton scattered X-rays are less sensitive to X-ray absorption effects in a sample compared to the intensity of Compton scattered X-rays. This characteristic makes the technique suitable for determining the Li concentration in a large cell.
This work was supported by the Development of System and Technology for Advanced Measurement and Analysis program under Japan Science and Technology Agency and MEXT KAKENHI Grant Number 24750065.

Fossil fuel reserves are unevenly distributed and running short worldwide. Salt that is the raw material of sodium metal is in the sea over the world, and it is not necessary to worry about the maldistribution and exhaustion. Seawater contains salt most after fresh water, which is the raw material of sodium and is never drained. Sodium produced with seawater is transported to a thermoelectric power station, where a large amount of hydrogen is generated immediately by adding water on the sodium for power generation. Hydrogen can neither be stored nor transported at room temperature under the atmospheric pressure, unlike coal and oil. The storage and transportation barriers of hydrogen are cleared by sodium “Source of Hydrogen” produced by seawater from thermal discharge of nuclear power plant.
179 nuclear reactors, which are equivalent to 40% of the total operating reactors in the world, use seawater for cooling. Many nuclear power plants are located along the cost-land because they use a huge amount of seawater for cooling. A nuclear reactor that has a capacity to generate electric power of one million kW uses about six million tons of seawater for cooling and returns hot water discharge whose temperature increased by 70C to the sea daily. The volume of the Pentagon is 2.18 million m³, so one reactor uses seawater three times as much as the volume of Pentagon per day. The hot seawater discharge is a repository of resources.
Therefore, a new technology for manufacturing an energy source from hot seawater discharge of a nuclear power plant is proposed. The seawater of six million tons contains followings: fresh water 5.4 million tons ($5.4 million in market price), sodium 65,000 tons ($975 million), sulfuric acid 17,000 tons ($12 million), hydrochloric acid 128,000 tons ($64 million), and magnesium 7,700 tons ($31 million). The minerals to be recovered from the six million tons are worth of 1.091 billion dollars in market price. More attractive resource is contained in the hot water discharge. It is heat energy accumulated, 42 billion kcal, and which costs 3.4 million dollars if generated by oil. It is absolutely a waste to keep discharging the hot seawater.
Taking advantage of the characteristics of seawater, sodium metal is manufactured directly by producing salt from seawater and subjecting the salt to molten-salt electrolysis by electric power at midnight of nuclear plant.
The sodium metal is transferred to a thermal power plant decentralized in each consumption place and brought into reaction with water to generate a large amount of hydrogen for hydrogen combustion power generation, and the waste, sodium hydroxide, is supplied to the soda industry as a raw material.
Besides, the hydrogen-fueled combustion turbines emit nothing but water, no CO₂ or radioactivity. It will contribute to the environmental protection of the earth as an environmentally friendly power plant.

The vanadium redox #64258;ow battery (VRFB) is one of rechargeable flow batteries that conducts vanadium ions in different oxidation states to store chemical potential energy and generate electrical energy or vice versa. It has been recently attracted as a large scale energy storage system for renewable power generation. One of issues on VRFB could be ion-exchange membranes to prevent the mixing of redox couples and to conduct ions to meet the oxidation states of vanadium ions. To increase voltage and columbic efficiency, the ion-exchange membranes should show low Ohmic resistance and low permeability of vanadium ions, respectively. However, the ion-exchange membrane should have good chemical stability due to highly acidic environment of dioxovanadium ions. In this study, the pore filling membrane was developed as separator by introducing several polymers such as perfluorinated sulfonic acids and crosslinked hydrocarbon polymers into thin porous polyethylene substrate to reduce Ohmic resistance by keeping the permeability of vanadium ions minimum. In addition, the effect of the properties of pore-filling membranes such as the water uptake, ion exchange capacity, proton conductivity, and permeability of vanadium ions on single cell performance were investigated.
REFERENCES
1. Wei, W., Zhang, H., Li, X., Zhang, H., Li, Y., & Vankelecom, I., Physical Chemistry Chemical Physics, 2013, 15.6, 1766-1771.
2. Tian, B., C. W. Yan, F. H. Wang., Journal of Membrane Science, 2004, 234.1, 51-54.
3. Li, Z. et al., Journal of Power Sources, 2014, 257, 221-229.

Energy storage provides Energy when it is needed just as transmission provides energy where it is needed. With the increasing penetration of variable renewable generation storage is now becoming one of the hottest topics in the utility industry. Research on materials and devices has increased cost effectiveness, cycle life and safety. Besides Li-ion batteries, flywheels, flow batteries, and advanced lead-carbon batteries are being deployed. Following small scale demonstration projects, markets are now gradually taking shape. At the same time changes in the regulatory framework result in more equitable valuation of storage benefits. The presentation will discuss multi-megawatt applications of a variety of energy storage technologies. Major recent storage facilities constructed in Texas, California, Pennsylvania, and New Mexico constructed under the ARRA stimulus program will be presented. As major players begin deploying increasingly more substantial storage projects, operators are recognizing their value for ancillary services. In particular, smoothing and ramping of wind and solar PV are being addressed. Emergency preparedness through storage microgrids is another important development. There are now over 900 storage projects listed on the Global Energy Storage Data Base. But with the new California mandate for 1.3MW of deployment, we can expect an exciting upsurge in storage research and many new projects to be realized. Storage will make renewables dispatchable and enable deeper penetration. It will also make the grid more resilient, improve asset utilization, and prevent outages

Current Indian energy systems encountering multiple challenges, including insufficient transmission and distribution capacity, not meeting today&’s energy demand, low energy access to rural sector and continue to depend on fossil fuel combustion. The way to address these issues is the following, the use of more renewable energy sources and uses more energy efficient devices. The Govt. of India has set aggressive directions to deploy Renewable energy sources in most part of the country based on availability. However, the most generic problem associated with Renewable energy sources is the inability to schedule their generation and therefore energy storage technology is playing a crucial role to help the situation.
Energy storage has become a most important driver of Indian energy strategy currently, during commence of several new project initiatives including smart grid and electric vehicles, as well as new programs on village electrification by on-site use of solar energy. In research arena, among the various electric energy storage systems, advanced batteries are set to attract the greatest interest now and in the near future. This is because of their flexibility in use, allowing for their employment in grid balancing and connecting intermittent renewable energy generators to the main electric grid. Therefore, current talk will highlight a range of energy storage technologies available today and analyze their cost and performance, along with focus on new concept that can change the current energy scenario based on Indian climate condition.

The work reported in this paper aims to establish a relationship between materials properties and device level performance for thermal energy storage. Particular focus is on the use of composite materials for medium and high temperature thermal energy storage (TES). The composite materials consist of a molten salt based phase change material, a thermal conductivity enhancer and a skeleton material for shape stabilization. Such materials offer an excellent combination of energy density, power density and mechanical properties and have a number of potential applications including solar thermal power generation, industrial waste heat recovery and electrification of heating. Both mathematical modelling and experiments are carried out to address the across length scale problem. The modelling work considers TES materials with a range of properties and TES components made of different sized and shaped TES composite modules. The experimental work uses a carbonate based composite material with graphite and MgO acting as the thermal conduction enhancer and the shape stabilizer, respectively. It shows that a superior TES material does not mean a superior TES device in many cases.

In 2010, a new vanadium redox flow battery chemistry using chloride-containing supporting electrolytes was invented at Pacific Northwest National Laboratory.^1,2 By adding a certain amount of chloride anions into the vanadium ions supporting solutions, stable V-Cl complexes form.
This new chemistry substantially improves the electrolyte stability over a significant wider range of temperatures, eases the system operation requirements and thus improves the system reliability and durability. It practically doubles the system energy capacity, allowing compact product design with 5X footprint reduction, and further enhances VFB safety through containerization and onsite chemical volume reduction. This technology was transferred to UniEnergy Technologies, LLC in 2012, and won the US Government&’ highest Award of Excellence in Technology Transfer in 2013.
With this advanced technology, the first compact vanadium AC battery, UET&’s 500 kW 4 hr Uni.System^TM, was successfully developed in 2014. This system has many unique features, including
Factory integration: precision assembly & QC
Excellent safety: non-flammable, aqueous electrolytes; built-in secondary containment
Temperature agnostic: -40 °C to +50 °C
SOC agnostic: full capacity access
Plug & Play: rapid, low cost deployment
Excellent Availability: no stripping etc. required
20-year design life: unlimited cycles
100% recyclable: disposal contract included
In this presentation, the detail parameters and performance of this system will be discussed.
1. Li^*, Kim, Wang, Vijayakumar, Nie, Chen, Zhang, Xia, Hu, Graff, Liu, Yang^*, Advanced Energy Materials, 1, 394~400, 2011.8th International Vanadium Symposium: Chemistry, Biological Chemistry, & Toxicology (vanadium8.org)
2. Kim, Vijayakumar, Wang, Zhang, Chen, Nie, Chen, Hu, Li^*, Yang^*, Phys. Chem. Chem. Phys., 13, 18186-18193, 2011.

Quinone-based flow batteries exhibit rapid redox kinetics, require no electrocatalyst, and contain inexpensive redox active materials, making them attractive candidates for large-scale electrical energy storage [1]. The performance of several substituted quinone/hydroquinone negative electrolyte materials are compared in an aqueous flow battery coupled with Br₂/HBr as the positive electrode. The use of 9,10-anthraquinone 2-sulfonic acid (AQS) enabled construction of a flow battery exhibiting an open circuit voltage exceeding 1.0 V . Initial findings are reported for a flow battery using as the negative electrode 1,8-dihydroxy-9,10-anthraquinone 2,7-disulfonic acid, which is reported to have charge transfer kinetics significantly faster than for 9,10-anthraquinone 2,7-disulfonic acid [1]. These experimental results are compared to a computational model which will guide future work to improve cell performance through cell design.
[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

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. Although continuous progresses have been made in the aqueous flow battery technologies, their system energy density has hardly improved over the years.^[1] Recent research on the non-aqueous electrolyte has offered wider electrochemical stability windows and thus higher cell voltages (>2.0V), but the low solubility of the active redox species in the non-aqueous electrolytes has largely prevented the high energy densities from being achieved (in most cases less than 0.1 M, corresponding to an energy density of 5 Wh L^-1 even at a higher cell voltage). Other challenges also include flammable nature, requirement of hermetic sealing, and low conductivity (which leads to current density at least one order of magnitude lower than the current aqueous system (< 0.5 mA cm^-2)) of the non-aqueous electrolytes, which further limit the development of the non-aqueous systems. A high energy density aqueous flow battery with high safety is therefore still critically needed. In this work, we report an aqueous flow battery based on the redox reactions between Zn/Zn²⁺ and I^-/I_x^-(xge;3). The proof-of-concept ZIB could reach a high energy density of 322 WhL^-1 at the solubility limit of ZnI₂ in water. We demonstrated that charge and discharge energy densities of 245.9 Wh/L and 166.7 WhL^-1, respectively, can be achieved, which is nearly 10/7 times higher than that of the current aqueous flow battery systems (VRB: ~25 WhL^-1) ^[2] while maintaining the high safety with no hazardous materials and strong acids.
References:
[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.

Flow batteries are attractive candidates for grid-level storage due to scalability, flexibility, ability to decouple stored energy from power, quick response time and long life. Lithium polysulfide flow (and semi-flow) batteries are one candidate system with potential to achieve high energy and low cost. Thin film graphitic carbon electrodes were used as a model surface to examine formation of polysulfides and sulfides. Stress evolution in a lithium polysulfide battery electrode is measured during electrochemical cycling using a Multi-beam Optical Stress Sensor (MOSS) through measurement of wafer curvature. A significant reversible and irreversible stress response is observed during cycling. An irreversible stress is observed at lower potentials, which are associated with the formation of sulfides. Reversible stress response is seen during voltage holds at 2.5V, while capacity does fully not reverse. Kinetic processes of the sulfur and polysulfide regimes are explored using cyclic voltammetry and voltage holds. Post-mortem samples are analyzed using RAMAN and electron microscopy to investegate the effect of sample growth parameters on electrochemical performance.

The introduction of quinone molecules to aqueous flow batteries points out a promising path toward massive electrical energy storage at low cost, as illustrated by the performance of a non-optimized flow cell based on 9,10-anthraquinone-2,7-disulphonic acid and hydrobromic acid [1]. Interactions among various species in the electrolytes imply that cell behavior is not simple. Here we report the dependence of the voltage and power density outputs, and various measures of efficiency, upon cell engineering and operating parameters. Loss mechanisms, including the crossover of bromine through the membrane, are also evaluated. The understanding developed by these studies has enabled improved cell performance.
[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

Lithium-ion batteries (LIBs) have been extensively used, but their applications are usually limited by energy density especially for high-quality electronic devices and electric vehicles. The limitation of energy density is believed to 300 Wh/Kg. Developing LIBs with high energy density is extremely important and urgent for energy storage. Cathode and anode materials are crucial for the LIBs to achieve high energy density. In order to meet the needs of high energy density, the cathode and the anode are both required to have a high specific capacity. On the other hand, the match among the electrode materials and battery design are also important to get high energy density. Here, we compare several electrode materials and introduce their development in China.
Among the cathode materials, the layered oxides LiNi_xCo_yMn_1-x-yO₂ (NCM) or LiNi_xCo_yAl_1-x-yO₂ (NCA) are attractive due to high energy density. Increasing Ni content is favorable to achieve high capacity. However, cationic disordering between Ni and Li ions is the key problem. Synthesis method is crucial to avoid the disordering. Sol-gel and coprecipitation technique with proper precursors are introduced to achieve high-quality layered cathode materials. Li-rich Mn-based layered oxides with formula xLi₂MnO₃×(1-x)LiMO₂ (M=Co, Ni, Mn) are also potential cathode materials for high-energy LIBs, which show specific capacity as high as 300 mAh g^minus;1, but poor rate capability and cycling stability limit their large-scale application in LIBs. It is generally known that composition optimization, particle nano-crystallization and surface modification are effective ways to improve the electrochemical performance. Nanomaterial fabrication and surface modification are employed to improve the performance. Several synthesis methods such as gel-assisted combustion, self-template route, large-scale co-precipitation have been developed.
For the anode materials, silicon and metal oxides such as SnO₂, MoO₂ etc. exhibit very high specific capacity, but serious volume expansion during charge/discharge process leads to pulverization of electrode and hence the capacity decay. For practical application, carbon-based anode materials show a great promise. Silicon-incorporated carbon is a good choice to achieve high capacity. Hard carbon is another alternative candidate for commercial graphite anode. Heteratomic doping and microstructure design are effective for performance improvement.

The U.S. Department of Energy has set forth the energy density target of 500 Wh/L at a cost of $125/kWh for widespread EV implementation. Li ion batteries have been identified as the most suitable technology due to their high energy density and high power density relative to other battery technologies. However their high cost, poor safety characteristics, and capacity fade during cycling remain major challenges. To meet the energy density and cost requirements of EVs will require development of materials with specific capacity above 200mAh/g and voltages vs. Lithium above 4.5V with compatible electrolytes. XALT Energy has developed Li ion cells which achieved 620 Wh/L, a significant advancement towards the DOE target. We believe the cost target will be more attainable by manufacturing cells of large format. A lithium- and manganese-rich nickel-manganese-cobalt oxide (LMR-NMC) cathode material with a core-shell Mn gradient could be charged to 4.4 V and output a specific capacity of >230 mAh/g. Utilizing a high-capacity Si/C composite material as the anode, this cell has retained >95% of its capacity after 300 1C/1C cycles. Moreover, DSC tests showed that XALT Energy cathodes had good thermal stability when charged at 4.4 V. Future work will continue to modify the electrolyte and explore Si/C composite anodes to achieve even greater cycle life in large format cells.

Since the first commercialized about twenty years ago, rechargeable lithium-ion batteries (LIBs) have become widespread power sources for portable devices used in daily life. They are now beginning to enter the market in the transportation sector, and for large scale energy storage. However, these applications increase the demands on electrical energy storage devices, calling for higher power density and energy density.
To enable faster ion diffusion and electron transport and lead to the improvement of power density of Li₃V₂(PO₄)₃ (LVP), our group has proposed several optimization strategies. The carbon-coated LVP with a continuous carbon network was prepared by using acetylene black as the template and PEG as the surface medication reactant. The prepared LVP nanospheres exhibit impressive rate capability and cycling stability resulting from the continuous carbon network and carbon coating layer. When cycled at a rate as high as 30 C the capacity can reach up to 87 mAh g^-1, and after 5000 cycles at a rate of 5 C the capacity is still maintained at 79 mAh g^-1. For increase the Li⁺ tansport, novel bicontinuous hierarchical LVP/C mesoporous nanowire (LVP/C-M-NW) structure was prepared by directly in situ carbonized surfactant along with the crystallization of LVP. Such novel LVP/C-M-NWs architecture provides bicontinuous electron/ion pathways and large electrodeminus;electrolyte contact area for rapid Li⁺ diffusion and electron transport. Meanwhile the robust structure stability facilitates the strain relaxation upon prolonged cycling. As a cathode for lithium-ion battery, the LVP/C mesoporous nanowires exhibit outstanding high-rate and ultralong-life performance with capacity retention of 80.0% after 3000 cycles at 5 C, even at 10 C, it still delivers 88.0% of its theoretical capacity. Futhermore, we developed a 3D hierarchical carbon-decorated LVP structure. The unique architecture can provide the continuous electron conduction enabled by hierarchical carbon, rapid ion transport enabled by electrolyte-filled macro/mesopore network, and a buffered protective carbon shell of the active material particles. Our work indicates that this hierarchical carbon-decorated LVP is one of the most attractive cathodes for practical applications.
Besides, we demonstrate that ultralong LiV₃O₈ nanowire cathode materials synthesized by topotactic Li intercalation in H₂V₃O₈ are capable of excellent high-rate performance. The LiV₃O₈ nanowire cathode showed excellent high-rate performance. A specific discharge capacity of 137 mAh g^-1 can be obtained at a current density of 2 A g^-1, and the capacity is able to stabilize at 120 mAh g^-1 even after 600 cycles. The excellent performance can be attributed to the low-charge-transfer resistance, good structural stability, large surface area and suitable degree of crystallinity.

Lithium-ion batteries (LIBs) have become a critical part of many now-ubiquitous technologies, such as mobile electronics, thanks to their relatively good energy and power densities and cycle lives. Growth of new and demanding applications such as electric vehicles and grid-scale energy storage has prompted further development of high-performance battery systems, including low-cost, high-energy lithium-sulfur (Li-S) batteries and phosphorous anodes for sodium-ion batteries (SIBs).^[1,2] However, these next-generation batteries suffer from serious issues that have thus far prevented their practical application. In turn, many of these issues stem from the formation of an unstable or poor-quality solid-electrolyte interphase (SEI) on one or both electrodes, prompting the use of novel electrolytes and additives as means of improving SEI formation.^[2,3]
In our work, we have investigated fluorinated electrolytes for several next-generation battery systems, both determining their effects on performance and delving into the mechanisms behind these effects. Use of bis(2,2,2-trifluoroethyl) ether as an electrolyte co-solvent for Li-S batteries was found to significantly decrease self-discharge, likely due to the SEI having a more robust composition and morphology.^[4] This contrasted sharply with the high self-discharge observed when using just the conventional SEI-building additive lithium nitrate. In addition, use of a fluorinated carbonate electrolyte for phosphorous anodes in SIBs was found to significantly improve cell stability and prevent serious side-reactions. Further investigation showed significant differences in the SEI composition, morphology, and stability in cells with fluorinated and non-fluorinated electrolytes, to which much of the enhanced performance can be attributed. In addition, severe sodium deposition was observed in cells with non-fluorinated electrolyte, which has critical implications for the safety and performance of these SIB systems. These findings can provide guidance on further work toward improving SEI formation in next-generation battery systems, thus pushing these systems closer to practical application.
[1] S. Chen, F. Dai, M. L. Gordin, D. Wang, RSC Adv.2013, 3, 3540-3543.
[2] N. Yabuuchi, Y. Matsuura, T. Ishikawa, S. Kuze, J.-Y. Son, Y.-T. Cui, H. Oji, S. Komaba, ChemElectroChem2014, 1, 580-589.
[3] V. Etacheri, O. Haik, Y. Goffer, G. A. Roberts, I. C. Stefan, R. Fasching, D. Aurbach, Langmuir2012, 28, 965-976.
[4] M. L. Gordin, F. Dai, S. Chen, T. Xu, J. Song, D. Tang, N. Azimi, Z. Zhang, D. Wang, ACS Appl. Mater. Interfaces2014, 6, 8006-8010.

Na-ion batteries, because of the high abundance and uniform geographic distribution of Na sources, are regarded as potentially low-cost energy storage devices and have attracted great attention for stationary applications. Despite all the efforts, developing stable and high energy electrode materials for reversible Na ion insertion and extraction remain significantly challenging. Recently, NASICON structured Na₃V₂(PO₄)₃ have been demonstrated to be a good cathode candidate of high working voltage of ~3.4V and a theoretical capacity of ~117 mAh/g. Yet it suffers from a low conductivity and usually needs large amount of carbon in electrode preparation. Here, we synthesized Na₃V₂(PO₄)₃-graphene nanocomposite and demonstrated its excellent cycling stability and rate performance as cathodes for Na-ion batteries. A capacity of ~102 mAh/g was obtained at 0.5C current density and the capacity retention was ~99% after 1000 cycles. The capacity at 2C rate is ~70 mAh/g.

Aluminium modified poly(ureamethylvinyl)silazane were blended with carbon nanotubes and pyrolyzed to synthesize SiAlCN-CNT composite. The structural and chemical characterization of the composite prepared were carried out using electron microscopy, XRD, and FT-infrared spectroscopy. The SiAlCN-CNT composite anodes showed stable charge capacity of 850 mAh/g at 100 mA/g and 550 mAh/g even at high current density of 10000 mA/g. The average columbic efficiency (second cycle onwards) was observed to be approx. 99%.

Here we provide the first report on several compositions of ternary Sn-Ge-Sb thin film alloys for application as sodium ion battery (aka NIB, NaB or SIB) anodes, employing Sn50Ge50, Sb50Ge50 and pure Sn, Ge, Sb as baselines. Sn33Ge33Sb33, Sn50Ge25Sb25, Sn60Ge20Sb20 and Sn50Ge50 all demonstrate promising electrochemical behavior, with Sn50Ge25Sb25 being the best overall. This alloy has an initial reversible specific capacity of 833 mAhg^-1 (at 85 mAg^-1), and 662 mAhg^-1 after 50 charge - discharge cycles. Sn50Ge25Sb25 also shows excellent rate capability, displaying a stable capacity of 381 mAhg^-1 at a current density of 8500 mAg^-1 (~ 10C). A survey of published literature indicates that 833 mAhg^-1 is among the highest reversible capacities reported for a Sn-based NIB anode, while 381 mAhg^-1 represents the most optimum fast charge value. HRTEM shows that Sn50Ge25Sb25 is a composite of 10 - 15 nm Sn and Sn-alloyed Ge nanocrystallites that are densely dispersed within an amorphous matrix. Comparing the microstructures of alloys where the capacity significantly exceeds the rule of mixtures prediction to those where it does not, leads us to hypothesize that this new phenomena originates from the Ge(Sn) that is able to sodiate beyond the 1:1 Na:Ge ratio reported for the pure element. Combined TOF-SIMS, EELS TEM and FIB analysis demonstrates substantial Na segregation within the film near the current collector interface that is present as early as the second discharge, followed by cycling - induced delamination from the current collector.

Magnesium (Mg) based rechargeable batteries have been considered as one of most promising battery technologies, which could provide low-cost, safe and sustainable way to store electric energy for transportation and grid applications. Over the past few years, substantial progresses have been achieved for rechargeable Mg batteries. However, the practical application of such Mg rechargeable batteries is still facing great challenges, due to limitations of promising cathode materials. In here, we present a hybrid battery technology that combine Mg and Li electrochemistry. A Mg/Li hybrid battery consists of a Mg anode, a lithium-intercalation cathode and a dual-salt electrolyte with both Mg²⁺ and Li⁺ ions. Our results show that Mg/Li hybrid batteries were able to combine the advantages of Li-ion and Mg batteries, and delivered outstanding rate performance and superior cyclic stability.

The substantial advantages of Mg-ion battery systems (volumetric advantage of divalent ion, safe operation using Mg metal anodes) are offset by the severe challenges associated with achieving good Mg-ion mobilities at room temperature. We have therefore carried out fundamental studies of a family of previously unexplored potential cathode materials which contain octahedral Mg ions organized into one-dimensional ribbons in order to better understand the factors influencing Mg-ion mobility. Synchrotron and neutron diffraction studies on the pristine compounds have been carried out to accurately determine the structures of these compounds, as well as the degree of mixing of Mg and redox-active transition metals at crystallographic sites with an octahedral environment. Using these structures, potential diffusion pathways were identified using simple bond valence (BVS) sum difference maps. For the two compounds studied, the BVS difference maps correctly predicted the inertness of one structure and for the other, correctly identified one Mg crystallographic site as immobile and a second Mg site as mobile. The site-specific removal of Mg-ions was experimentally confirmed through the Rietveld refinement of diffraction data collected after demagnesiation was driven by mild thermal oxidation (200 - 500 °C). The latter compound was shown to have interstitial diffusion pathways whose ionic conductivity is expected to be robust against anti-site defects between Mg and transition metal ions, and is therefore considered to be a promising target for further improvement by chemical substitution.

Copper hexacyanoferrate (CuHCFe) is a Prussian blue analog of the type AB[M(CN)₆].nH₂0, where A is a cation that can be inserted or removed from the lattice, B and M are framework cations (e.g. Cuⁿ⁺, Feⁿ⁺), with B strongly bonded to [M(CN)₆]^3- units. The coordinated water molecules are an intimate part of the crystal structure and are essential to the structural integrity of the framework. As is characteristic of this class of materials, CuHCFe possesses large pore-volumes within the crystal structure, which makes it an excellent candidate for ion insertion and a promising battery electrode material for grid-scale energy storage (Wessells et al., Nature Communications, 2:550, 2011). However, the structural underpinnings of its highly reversible ion insertion behavior are poorly understood despite being important in the broader context of energy storage. In order to characterize the hydration and disorder of the insertion (A) cations (Rb⁺, Pb²⁺ and Y³⁺ ions) within the framework, we collected XAS data at the insertion ion edges of the fully reduced CuHCFe compounds. The EXAFS data suggest that all ions in this study indicate some degree of hydration. The Rb K edge EXAFS displays backscattering at distances beyond 4 Å indicating a relatively high degree of ordering for the Rb⁺ ion, while the signal falls off rapidly for both Pb²⁺ and Y³⁺ ions indicating a less well-defined environment for these multivalent ions. Even the location and site-occupancies of insertion ions inside the crystal lattice continue to be debated, which we will discuss along with XRD data on pristine and electrochemically reduced CuHCFe. These studies are aimed at obtaining a better understanding of mono and multivalent ion insertion in CuHCFe and related framework materials.

The integration of renewable energy such as solar and wind power into the electricity grid faces the challenge of intermittent electricity output. Storing the electricity during times of excess production and releasing the electrical energy to the grid during peak demand is a potential solution. Rechargeable batteries are very attractive for energy storage because of their high energy efficiency and scalability.
Since large-scale electrical energy storage requires hundreds of gigawatt-hours to be stored, the batteries for this application must be inexpensive, robust, safe and sustainable. None of today&’s mature battery technologies meet all of these requirements. In this presentation, we will summarize the recent research advancements in three aqueous battery systems that have the potential to meet the demanding requirements of grid-scale energy storage: (1) alkaline iron-air battery, (2) the iron-chloride redox flow battery and (3) a new aqueous organic redox flow battery. These three battery systems satisfy the primary criterion of using of inexpensive or abundantly-available and sustainable materials for energy storage. The use of toxic heavy metals is completely avoided. These battery systems have demonstrated the potential of achieving high energy efficiencies and power density required for large-scale applications.

Grid-level energy storage demands a low-cost, safe, long cycle life battery chemistry. The Zn-MnO2 alkaline battery chemistry hits the first two targets. This type of battery has high energy density (comparable to that of a Li-ion battery) and low cost per kilowatt-hour. However, their rechargeability is limited by phase transformations which occur in the MnO2 cathode in the presence of zinc ions during discharge of close to one electron, which transforms it into an spinel phase, generally considered to be electrochemically inert. As a result, depth of discharge is limited to no more than 70% of the 1e- capacity of MnO2 at best, and in a large format cell typically no more than 0.5 e-.
We have developed a new morphology of MnO2 of mixed phase with better zinc stability (as compared to traditional gamma and delta MnO2) consisting of fine needle-like nanoparticles with very high rate capability (2C), cyclability and capacity (over 350 mAh/g), produced through a facile, one-step synthesis. In this presentation, we describe the crystal structure and electrochemical performance of this material, as well as the structural changes occurring during its use as an electrode material as characterized with synchrotron radiation. We compare its performance to that of other forms of MnO2, as well as the impact of “traditional” alkaline battery dopants. We have studied this material via in-situ and ex-situ X-ray diffraction and electron microscopy techniques.
With further development, this material, combined with either a zinc anode or an earth abundant, insoluble anode such as Fe or Cd, may allow for over 1000 cycles at a cost of less that $100/kWhr for a packed out cell.

The rapid growth of the integration of renewable energy sources such as wind and solar into power grids has spurred extensive research on the energy storage technologies that could improve grid reliability and utilization.^[1-3] Electrochemical batteries including lithium-ion, sodium sulfur and lead acid batteries are one of the currently deployed energy storage solutions for grid applications.^[4] However, the lithium-ion, sodium sulfur and lead acid batteries suffer from high cost, poor safety and limited cycle life, respectively. In contrast, aqueous metal-ion (specifically Li⁺ and Na⁺) batteries are potentially low-cost, safe and demonstrated to be long-life.^[5-11] Beyond monovalent metal-ion (Li⁺, Na⁺ and K⁺) systems, multivalent metal-ion (Mg²⁺, Al³⁺, etc.) systems are of equal or greater interest due to their potentially higher specific energy and energy density. In this paper, we propose and demonstrate several low-cost aqueous metal-ion (metal= Na, Mg, Al) rechargeable battery prototypes for grid energy storage.
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[2] B. Dunn, H. Kamath, J.-M. Tarascon, Science2011, 334, 928.
[3] G. L. Soloveichik, Annu Rev Chem Biomol Eng2011, 2, 503.
[4] “Grid Energy Storage - December 2013,” can be found under http://energy.gov/oe/downloads/grid-energy-storage-december-2013.
[5] J.-Y. Luo, W.-J. Cui, P. He, Y.-Y. Xia, Nat Chem2010, 2, 760.
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Batteries, regenerative fuel cells, supercapacitors represent electrical energy storage technologies for matching energy consumption with production especially for the integration of renewable sources. More than a century of research has identified hundreds of electrochemical redox active electrical energy storage materials, the most notable are Zn-MnO₂ primary batteries and lead-acid, nickel-cadmium, lithium-ion secondary batteries. Despite important advances, utility scale electrochemical energy storage technologies are too expensive on a price per energy unit per cycle basis to be used at large scale. The basis materials of batteries for large-scale storage must be low-cost, earth-abundant, and safe at the desired scale. The alkaline MnO2 cathode, typically found in low-cost consumer primaries, fulfills these requirements. The U.S. Department of Energy ARPA-E goals for large-scale storage are less than $0.10 per kWh per cycle and efficiency of the battery. A standard cylindrical alkaline cell costs roughly $20 per kWh. Thus an alkaline cell is a sufficiently inexpensive basis for large-scale storage. However, in this case an extended 5000-cycle life becomes the relevant engineering challenge.
Discharge of an MnO2 cathode involves many reactions, both chemical and electrochemical, and only certain of these are fully reversible. For example the proton insertion to MnOOH is usually assumed reversible. However, a subsequent solution-phase reduction to Mn(OH)2 can then lead to Mn3O4, which is considered irreversible. Confining the cathode cycling window to a well-controlled state-of-charge range involving only MnOOH can in theory result in perfect reversibility. Additionally, current distributions can result in locally high reaction rates in the electrode, and chemical reactions can be challenging to control, as they do not respond directly to the potential. In this paper we report studies of long-term cycling with prismatic zinc-manganese dioxide batteries. Cell energy efficiency was in the range of 80% or greater for all cells. The discharge end voltage was taken as a general metric of cell health, and in all cases evolved over time, generally decreasing with cell age. Under certain profile conditions, cells cycled uninterrupted for years with stable efficiency. In the early stages of cycling, a selection of cells was halted and material changes within the cells were analyzed. This information was combined with that from post mortem analyses of decommissioned cells. The goal was understanding the origin of the processes that most frequently lead to cell failure, and knowledge of the operating conditions at which these processes occur.

With an increasing demand for effective grd-scale energy storage system (ESS), development of large-scale and low-cost battery systems has become more critical. Rechargeable sodium batteries can offer a competitive solution to meet this demand and afford opportunities for widespread use of the renewable energy generation.

Despite a high capacity for energy storage, metal electrodes have had limited applications in batteries because of dendrite formation and other problems. In this paper, we report a new alloying strategy that can significantly reduce the melting temperature and improve wetting with the electrolyte, which allows the use of liquid metal as anode in sodium-beta alumina batteries (NBBs) at much lower temperatures (e.g., 95-175°C). Commercial NBBs such as sodium-sulfur (Na-S) battery and sodium-metal halide (ZEBRA) batteries typically need an operating temperature of 300 to 350°C, and one of the reasons is poor wettability of sodium on the surface of β"-Al₂O₃. Our combined experimental and computational studies suggest that a Na-Cs alloy can replace pure sodium as the anode material, which provides a dramatic improvement in wettability, particularly at lower temperatures (i.e., <200°C). Single cells with the Na-Cs alloy anodes exhibit great improvement in cycling life over those with pure sodium anodes at 175 and 150°C. The cells can even operate at 95°C, which is below the melting temperature of pure sodium. These results indicate that NBB can be operated at much lower temperatures with successfully solving the wetting issue. This work also suggests a new strategy to use liquid metals in advanced batteries that can avoid the intrinsic safety issues associated with dendrite formation on the electrode.

Sodium-Nickel chloride (Na-NiCl₂) battery is one of most promising stationary electric energy storage technologies. An important advantage of Na-NiCl₂ battery is that the cell is typically assembled in the discharge state to avoid the use of reactive, hazardous materials such as anhydrous nickel chloride and metallic sodium. Iron sulfide (FeS) has been widely used in Na-NiCl₂ battery as a cathode additive. However, despite the importance of using FeS in the Na-NiCl₂ battery, the mechanistic understanding of FeS still needs to be revealed. In here, extensive studies about the role of FeS for initial cell activation and degradation in the Na-NiCl₂ battery will be presented. The research focused on identifying the effects of FeS level for the electrochemical performance and morphological changes in the cathode. The x-ray photoelectron spectroscopy study along with battery tests revealed that FeS plays a critical role to properly activate the battery built in the discharge state. It was also found that an optimum level of FeS in the cathode resulted in minimum Ni particle growth and improved battery cycling performance.