Xiaolin Li, Pacific Northwest National Laboratory
Prashant Kumta, University of Pittsburgh
Xinping Qiu, Tsinghua University
Donghai Wang, The Pennsylvania State University
ACS Energy Letters | ACS Publications
Angstrom Thin Film Technologies LLC
Bio-Logic USA, LLC
Pacific Northwest National Laboratory
ET06.01: General Introduction, Reliability and Safety
Monday AM, November 26, 2018
Hynes, Level 3, Room Ballroom A
8:30 AM - *ET06.01.01
Materials for High Energy Li and Li-Ion Batteries
M. Stanley Whittingham1
State University of New York at Binghamton1Show Abstract
Over the last decade the energy density of lithium-based batteries has gradually increased, but commercially available cells have now topped out at around 200-250 Wh/kg at the cell level. I will describe several materials-centered approaches that will allow in excess of 300-350 Wh/kg and 700 Wh/l. First the carbon-based anode must be replaced by a higher capacity material, preferably lithium metal itself; we have found that tin-based anodes can achieve 50-100% greater capacity than carbons with coulombic efficiencies over 99.5%. Second on the cathode side, I will describe two options: two-electron systems using lithium, and high nickel NMCAs, both of which have theoretical energy densities of around 1 kWh/kg and have the capability of attaining 1 kWh/liter. The safety aspects will also be covered. This work is supported by US DOE, BES-EFRC and EERE-VTO-BMR.
9:00 AM - *ET06.01.02
Reliability of Li-Ion Batteries for Grid Application
Daiwon Choi1,Alasdair Crawford1,Vilayanur Viswanathan1,David Reed1,Vincent Sprenkle1
Pacific Northwest National Laboratory1Show Abstract
Li-ion batteries are expected to play a vital role in stabilizing the electrical grid as solar and wind generation capacity becomes increasingly integrated into the electric infrastructure. In this work, different commercial Li-ion batteries based on LiNi0.8Co0.15Al0.05O2 (NCA), LiNixMnyCozO2 (NMC) and LiFePO4 (LFP) cathode chemistries have been tested under the grid duty cycle protocols recently developed for frequency regulation (FR) and peak shaving (PS) with and without being subjected to electric vehicle (EV) drive cycles. The lifecycle comparison derived from capacity, round trip efficiency (RTE), resistance, charge/discharge energy and total utilized energy of the battery chemistries will be presented. Furthermore, degradation mechanisms of different battery chemistries will be discussed. The results can be used as a guideline for selection, deployment, operation and cost analyses of Li-ion batteries used for different applications.
10:00 AM - *ET06.01.03
Mechanisms and Ramification of Overcharge on Battery Materials
Joshua Lamb1,Loraine Torres-Castro1,Mohan Karulkar1,June Stanley1
Sandia National Laboratories1Show Abstract
Overcharge testing has long been used as a standard abuse test evaluation for lithium ion batteries, which have notably poor tolerance for overcharge and overvoltage conditions. While this has historically been strictly an abuse test, large potential gradients created by high rate charge and discharge operations in electric vehicle and stationary storage applications may lead to areas of localized overcharge or overpotential on the electrodes. This work looks at high capacity (10 AH) prismatic pouch cells, applying overcharge from 105 – 200% total State of Charge (SOC), up to and including energetic thermal runaway of cells. The mechanisms of overcharge failure are investigated using electrochemical techniques including EIS and differential capacity measurements to evaluate the degradation and failure mechanisms that occur during the overcharge condition. This is supported with materials evaluations to further evaluate the impact of overcharge on the constituent materials.
Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
10:30 AM - ET06.01.04
Multifunctional Lithium-Ion Exchanged Zeolite Coated Separator for Lithium-Ion Batteries
Jiagang Xu1,Xingcheng Xiao1,Sherman Zeng1,Mei Cai1,Mark Verbrugge1
General Motors1Show Abstract
The skyrocketing price of cobalt pushes battery manufacturers to look back into low cost manganese containing positive electrodes. However, manganese dissolution has been considered as a critical problem for the majority of manganese containing positive electrodes. Although many efforts have been devoted to stabilizing the crystal structure and exploring new electrolyte additives, less progress has been reported so far. In this work, we have developed a novel multifunctional separator, targeting the root cause of manganese dissolution. A lithium-ion exchanged zeolite has been coated on polymer separator as the ceramic coating, which provides multi-functions to mitigate the issues arose from sequential scenario associated with manganese dissolution, including: 1. Trapping trace water: the high surface area in zeolite traps the trace water in the electrolyte, mitigating the hydrolysis of lithium salt and HF generation. 2. HF scavenger: in case of the HF already existing in the electrolyte, Al2O3 in the zeolite can preferentially react with HF as the scavenger due to the high surface area, therefore protecting the oxides in positive electrodes 3. Trapping Mn ions: in the worst scenario of Mn dissolved into electrolyte, the Li ion in zeolite will have the ion exchange with Mn ions in the electrolyte and trap Mn ions in the separator to avoid its damage to the SEI layer on anode side. In addition, lithium-ion exchanged zeolite separator can improve the wettability and thermal stability of the plain separator on which zeolite is coated. Based on this technology, we have demonstrated that Lithium-ion exchanged zeolite separator leads to the enhanced cycle performance (high capacity and Coulombic efficiency) of graphite/ (LiNi0.5Mn0.3Co0.2O2+LiMn2O4) full cells at both room temperature and elevated temperature, comparing with the plain separator and commercial alumina coated separator. The coin cell with Li-zeolite coated separator exhibits an average Coulombic efficiency of 99.89% and achieves a capacity retention rate of 78.3% after 500 cycles at 25 °C. We find out that a lower amount of manganese is present on the cycled graphite electrode when Li-zeolite coated separator is used, suggesting less side reactions resulted from Mn.
10:45 AM - ET06.01.05
Novel Battery Separators Enabled by Ultrathin, Robust Solid Electrolytes
Shaofei Wang1,Andrew Westover2,Sergiy Kalnaus2,Andrew Kercher2,Nancy Dudney2,William West3,Wyatt Tenhaeff1
University of Rochester1,Oak Ridge National Laboratory2,NASA Jet Propulsion Laboratory3Show Abstract
Solid electrolytes with low area specific resistance must be developed to enable high energy density lithium metal batteries. In addition to high ionic conductivities and large electrochemical stability windows, solid electrolytes also require robust mechanical properties to allow for large-scale production and successful integration into conventional lithium battery cell designs. To achieve these features, a novel solid electrolyte separator design was developed, in which a 50 - 100 nm fully dense solid electrolyte layer was coated onto microporous Celgard separators. The supporting Celgard made the solid electrolyte more robust and flexible, which enabled integration into coin cells. Due to its thinness, the resistance of the solid electrolyte layer was 5 - 10 Ω-cm2. The solid electrolyte also showed low interfacial resistance with liquid electrolyte. The total resistance of solid electrolyte-Celgard membrane was determined to be 40 Ω-cm2 in alkyl carbonate electrolytes, which is much lower than Garnet and Ohara solid electrolytes. The solid electrolyte membrane also was also shown to inhibit the crossover between anode and cathode in Li-S cells. The Li-S cell enabled by the new solid electrolyte membranes showed high coulombic efficiency and stable cycling performance. The advent of the new robust solid electrolyte paves the way for the commercialization of high energy density lithium metal batteries.
This work was supported by the ARPA-E IONICS program, U.S. Department of Energy, award DE-AR0000775.
11:00 AM - ET06.01.06
Long-Term Calendar Degradation in Li-Ion Batteries
Aziz Abdellahi1,Berislav Blizanac1,Brian Sisk1
A123 Systems LLC1Show Abstract
With the increased penetration of electrified vehicles in the automotive market, requirements pertaining to battery durability are becoming increasingly stringent. To meet the requirements of the automotive industry, lithium-ion batteries must exhibit extensive life before reaching a terminal state of capacity loss and impedance growth. For battery designers and manufacturers, it is therefore of paramount importance to understand and predict long-term battery cell degradation based on a necessarily limited set of accelerated degradation tests.
Long-term calendar aging, defined as the temperature-induced cell degradation in the absence of current, is especially difficult to predict at relevant battery operating temperatures (25oC – 45oC). Unlike cycling tests, which can be rapidly conducted to the end-of-life by removing rest periods between cycles, calendar tests cannot be directly accelerated. To this end, a variety of empirical and physics-based models have been developed to predict the long-term storage behavior of battery packs based on a set of accelerated storage tests conducted at high temperatures. However, the validity of these calendar predictions has not, to the best of our knowledge, been extensively studied against actual long-term storage data surpassing the 4 year mark.
In this presentation, we present a set of long-term storage experiments performed over the course of 4-to-6 years on LiFePO4/graphite cells, at various states of charge and temperatures. Analysis of the storage data sheds light on the long-term degradation mechanism in the cell, and demonstrates a transition between a reaction-controlled to a diffusion-controlled growth of the anodic solid electrolyte interphase (SEI). The dependence of state of charge and temperature on the degradation rate is clarified, and the predictive performance of empirical calendar life models is assessed. This work provides a mechanistic analysis of the nature of long-term degradation mechanisms in Li-ion batteries and paves the way towards an improvement of the predictive ability of empirical calendar life models. The conclusions of this study can also serve to understand long-term calendar degradation in higher-voltage NMC/graphite batteries, in which both the anode and the cathode may experience calendar degradation at high states-of-charge.
11:15 AM - ET06.01.07
Adaptive Current-Collectors for Safe High-Energy Rechargeable Batteries
Sean Doris1,Adrien Pierre1,Elif Karatay1,Warren Jackson1,Robert Street1
Palo Alto Research Center1Show Abstract
High energy density rechargeable batteries are critical for the widespread adoption of EVs, however their high energy density leads to an inherent safety risk if an internal short circuit (ISC) forms and releases all the energy in the battery in seconds. When an ISC occurs – from dendrite formation, cell deformation/damage, or a manufacturing defect – the entire battery capacity rapidly discharges. This release of energy leads to extremely high temperatures near the short that can induce thermal runaway, cell rupture or venting, and fire. While the use of shutdown separators can help mitigate ISCs in smaller cells, they are often ineffective in the larger, high-energy batteries used in EVs and grid storage applications. Rather than relying on thermally-induced shutdown that may fail to shut down regions of the battery far from the ISC, it is preferable to directly detect and stop the internal current that flows during an ISC. In this presentation, I will introduce our work on adaptive current-collectors, which allow for direct control over the local current that flows between the current-collector and the active material by simple printed electronic circuits. I will show how the electrical properties of printed electronics can be tuned to meet the demanding requirements of adaptive current-collectors, including low resistance during normal operating currents and high resistance under abuse conditions. Our simulations indicate that adaptive current-collectors can reduce the current flowing through ISCs by more than 90%, converting this catastrophic failure mode into a graceful one. In addition to enabling safe high-energy rechargeable batteries, the development of adaptive current-collectors will give battery users finer control over current flow at the sub-cell level, which is expected to improve battery reliability and rate capability.
ET06.02: All Solid-State Battery
Monday PM, November 26, 2018
Hynes, Level 3, Room Ballroom A
1:30 PM - *ET06.02.01
All-Solid-State Lithium Metal Batteries Utilizing Polyrotaxanes as New Family of Solid Polymer Electrolytes
Martin Winter1,2,Laura Imholt1,Gunther Brunklaus1,Isidora Cekic-Laskovic1
Forschungszentrum Juelich GmbH1,University of Münster2Show Abstract
Lithium metal constitutes an attractive anode material mainly due to its high theoretical specific capacity of 3860 mAh g−1, ten times higher than graphite (372 mAh g−1). The use of lithium metal in rechargeable batteries with typical liquid organic solvent based electrolytes suffers so far from severe safety problems associated with the formation of high surface area metallic lithium (HSAL) upon repeated charge/discharge. Solid polymer electrolytes (SPEs) designed to be compatible with lithium metal are able to mechanically suppress HSAL formation and are considered as viable alternative. Solvent-free SPEs exhibit advantages in terms of mechanical stability, operational safety and simplicity of cell design. However, application of polymer electrolytes to all-solid-state lithium ion batteries (ASS-LIBs) and all-solid-state lithium ion batteries (ASS-LMBs), requires improvements in respect to lithium ion conductivity, especially at ambient temperature.
Although high ionic conductivities can be achieved by high chain mobility linked to low molecular weight polymers, they are mostly too soft and therefore cause deterioration in mechanical stability of the SPE. In order to use low molecular weight polymers for fast lithium ion transport with sufficient mechanical strength at the same time, one strategy is related to utilization of a hyperbranched co-polymer where one segment represents a stable, hard backbone while the second segment is derived from a soft polymer with high ionic conductivities. With this in line, a new generation of Li+-conducting SPEs obtained from supramolecular self-assembly of PEO, cyclodextrin (CD) and lithium salt was designed and thoroughly investigated for application in lithium metal batteries (LMBs) and LIBs. When mixing an aqueous solution of PEO together with an aqueous solution of CD, a precipitate forms where the CD is threaded onto a PEO chain. The channel-type structure formed by self-assembly of PEO and CD can be used as the backb