TO IMPROVE SAFETY AND RELIABILITY OF BATTERY-POWERED SYSTEMS NOVEMBER 2016

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1 BATTERY RESEARCH TO IMPROVE SAFETY AND RELIABILITY OF BATTERY-POWERED SYSTEMS NOVEMBER 2016 Microsoft is investigating widespread reports of battery issues with its line of Surface Pro 3 devices. Reports of Surface Pro 3 battery drain originated in May, and some users were reporting that their devices only last up to an hour after a full charge. In late August, Microsoft released a firmware update to fix the battery problem. Even after the fix, some of the users have complained that the minute they unplug their Surface, the device shuts down. CNN Money Microsoft Surface Pro 3 Samsung has permanently halted the production and sales of it Galaxy Note 7 smartphone and has finally advised all customers to stop using the phones, Even before this announcement, Samsung s shares in South Korea fell more than 8 percent, its biggest daily drop since 2008, knocking $17 billion off the company s market value. The Federal Aviation Administration (FAA) has urged the passengers onboard aircraft to power down, and not use, charge, or stow in checked baggage, any Samsung Galaxy Note 7 devices, including recalled and replacement devices. All big four U.S. carriers have stopped providing the replacement Samsung Galaxy Note 7. Target and Amazon also have stopped selling the phone. Samsung had earlier conducted a thorough inspection in conjunction with their suppliers to identify possible failure causes. Samsung had even attempted to issue a software update for its Galaxy Note 7 to prevent overheating by limiting battery recharges to 60%. However, the real cause of problem has still not been reported or identified. These repeated incidents of battery fire emphasize the need of critical battery safety analysis techniques and standards. Non-destructive techniques including X-rays inspection can be really helpful in detecting any defects in internal battery structure during qualification phase. The CALCE Battery Group is dedicated to the research of battery safety and reliability using physics-of-failure and data-driven approaches to evaluate and predict battery performance and degradation. For questions related to CALCE s battery research, contact Prof. Michael Pecht (pecht@calce.umd.edu) or Dr. Laura Xing (yxing3@calce.umd.edu). INSIDE THIS ISSUE: BATTERY SAFETY INCIDENTS SAFETY REQUIREMENTS FOR TRANSPORT OF LITHIUM BATTERIES INVESTIGATION OF LITHIUM DENDRITE GROWTH MECHANISM FAILURE ANALYSIS USING 3-ELECTRODE CELL CALCE RESEARCHERS WIN PROPOSALS AND PAPER AWARDS DR. ELHAM SAHRAEI FROM MIT VISITS CALCE VISITING SCHOLARS & LAB SERVICES PROJECTS CALCE BATTERY DATABASE CALCE RECENT BATTERY ARTICLES JOIN CALCE

2 NOVEMBER 2016 PAGE 2 Safety Requirements for Transport of Lithium Batteries CALCE, with Shanghai Ocean University and BFH-CSEM Energy Storage Research Centre, Bern Universities of Applied Sciences, has conducted a comprehensive study on the international and key national (U.S., Europe, Korea, and China) air, road, rail, and sea transportation requirements for lithium batteries. Lithium batteries are identified by United Nations (UN) regulations as dangerous goods when they are transported. Safe and reliable transport of batteries from production sites to suppliers and ultimately to the end-consumers must be guaranteed at all times. To minimize the risks inherent in commercial transportation of lithium batteries, battery manufacturers, energy storage businesses, and individual end-users must understand and comply with shipping regulations for dangerous goods. However, we find that transportation regulations are not consistent across countries. Moreover, national regulations of individual countries are not consistent with international regulations. Lithium batteries are classified under UN category 9 of dangerous goods because they are thermally and electrically unstable if they face uncontrolled environmental conditions and are mishandled during transportation. Failures in batteries include electrolyte leakage, heat production, venting of toxic gases, fire, and explosions. Many product sheets include three major hazards identifications: (a) chemical: liquid, and gas leakage; (b) electrical: short-circuit, high voltage, and battery management system failure causing battery heating, thermal runaway or system power loss; and (c) mechanical: vibration, air pressure, shock, and deformation causing release of hazardous materials. During accidents, lithium batteries can be unsafe for humans and for the environment.. The CALCE report includes: (1) information on packaging, hazard communication, handling methods, and other details for shippers to better understand and comply with the international regulatory requirements for transporting lithium batteries; (2) summary of the differences among U.S., European, and Chinese regulations for different kinds of lithium batteries and for various transport modes; (3) comparisons between U.S., European, and Chinese transport regulations, which will help in developing national and international policies and designing criteria for testing, packaging, marking, labelling, documentation, and handling of batteries for transport; (4) guidance for preparing new and generic regulations across borders and for overcoming the flaws in the existing exhaustive regulations. For more information on safety requirements for transportation of lithium batteries, contact Dr. Yinjiao (Laura) Xing (yxing3@calce.umd.edu) or Prof. Michael Pecht (pecht@calce.umd.edu).

3 CALCE BATTERY NEWSLETTER PAGE 3 In Situ Investigation of Lithium Dendrite Growth Internal short circuits caused by lithium dendrite formation are considered one of the most severe battery faults that can lead to battery heating and thermal runaway incidents. Lithium dendrites are metallic microstructures that form on the negative electrode during the charging process. Dendrites can form in a Li-ion battery when it is overcharged or charged at low temperatures. In order to improve Li-ion battery safety, it is necessary to study and understand lithium dendrite formation mechanism. For this purpose, an in situ observation method is being used in our study to detect dendrite formation at various current densities and temperatures. The relationship between the applied current density and the dendrite growth rate is the research focus in the first phase of this study. In order to determine the dendrite growth rate, a symmetrical lithium cell (both the positive and negative electrodes are made of lithium metal) are being used. These cells are charged at constant current to produce lithium dendrites. 2 mm Dendrites The dendrite morphology evolution process is shown in Fig. 1: (a) the original state; (b) dendrites at 15 mins; (c) dendrites at 30 mins. The scale bar is applied to all three images, and the red arrows in (c) indicate the position where the internal short circuits occurred. a (0 min) b (15 mins) c (30 mins) Fig. 1.Dendrite growth during constant charging test. 1.2 These results are consistent with the measured voltage data (Fig. 2) during the testing. Before the occurrence of internal short circuits, the voltage remained almost constant. At 0.55 hours, there was a sudden drop of the voltage, which indicates the lithium dendrite growth triggered internal short circuits. The red circle shows the time at which the dendrite-triggered internal shorts occurred. Voltage (V) Internal shorts Time (hours) Fig. 2. Measured voltage data during the charging test. For more information on this lithium dendrite study, contact Dr. Yinjiao (Laura) Xing (yxing3@calce.umd.edu) or Prof. Michael Pecht (pecht@calce.umd.edu).

4 NOVEMBER 2016 PAGE 4 Failure Analysis of Commercial Li-ion Batteries Using a Three-Electrode System CALCE has been analyzing the failure behaviors and mechanisms of commercial Li-ion batteries based on a three-electrode system. The failure of Li-ion batteries can limit their performance and cause fire or explosion. In order to identify the major failure mechanisms of the batteries and relate the attributes of each electrode to the failure of the batteries, a three-electrode system with a reference electrode was used to quantify the evolution of both the voltages and impedances of each electrode at different aging levels. A commonly used commercial Li-ion battery (LiFePO 4 /graphite) was first disassembled in a glovebox to obtain the cathode and anode materials. Then, the materials were reassembled into a threeelectrode cell (ECC-Ref) for testing. Fig. 1 shows the three-electrode cell test bench, which consists of an electrochemical test system, an Arbin BT2000 battery tester, and a field emission SEM coupled with an EDS. SEM/EDS was used to observe the surface morphology and elements of the pristine and cycled electrode materials. A charging/discharging cycling test was conducted. During each cycle, the cell was charged under a constant current Fig. 1. Three-electrode cell test bench. constant voltage (CC-CV) charge mode, and then discharged at a constant current to 2.5 V. A reference performance test was performed after every five cycles to obtain the cell capacity and impedance changes of each electrode. (a)cathode (b)anode Fig. 2. Impedances of the cathode and anode under different cycle numbers. The impedances and voltages of individual electrodes will be analyzed under various degradation levels of battery. Finally, the failure mechanism of the battery can be explained and the contribution of each electrode to the failure of the battery can be clearly identified. For more information on three-electrode testing, contact Dr. Yinjiao (Laura) Xing (yxing3@calce.umd.edu) or Prof. Michael Pecht (pecht@calce.umd.edu).

5 CALCE BATTERY NEWSLETTER PAGE 5 Dr. Yinjiao (Laura) Xing wins the 2015 Applied Energy Award for Highly Cited Research Papers Dr. Xing s research paper titled State of charge estimation of lithium-ion batteries using the open-circuit voltage at various ambient temperatures published in 2014 in Applied Energy journal has been recognized as a highly cited research paper and has won the 2015 Applied Energy Award. Dr. Xing is currently working with CALCE Battery Group as Research Associate. She received her Ph.D. in Systems Engineering and Engineering Management (2014) at City University of Hong Kong, Hong Kong. Her research focuses on battery system monitoring, modelling and failure analysis for the purpose of improvement of battery system reliability and operational performance. The awarded paper proposes a novel method for battery state of charge (SOC) estimation using the interrelation of Open Circuit Voltage (OCV), SOC and temperature. The proposed method offers advantage over the conventional OCV-SOC relation based model by taking the effects of temperature into account. X-wave Innovations and CALCE team win two key battery contracts for NASA and the U.S. Navy NASA seeks intelligent monitoring of hybrid and/or all-electric propulsion systems, as well as methods to significantly extend the life of electric aircraft propulsion energy sources. Lithium-based batteries will play a key role in these systems due to their high energy and power densities. Research has focused on achieving accurate and stable long-term estimation of cell state of charge (SOC), state of health (SOH), and remaining useful life (RUL), and these efforts have achieved success accuracies below 3% error are common today. However, new approaches are needed to intelligently use the estimated states for battery health and life performance improvements. CALCE has answered this need by developing a controller that uses the estimated states to realize gains in battery health and life. The key innovation of the proposed approach lies in the integration and implementation of CALCE s accurate model-based and data-driven algorithms. An accurate state estimation combined with intelligent health management will allow the efficient utilization and successful adoption of Li-ion technology for aircraft. Electric aircraft technology will be an important step toward sustainable future by means of reducing the reliance on fossil fuels. X-wave Innovations (XII), CALCE, and Boeing answered the call for one of the U.S. Navy s small business innovation research (SBIR) Phase I projects. A novel battery early-failure sensor tag (BEST) will be developed that combines low-power and low-cost in situ non-destructive testing/evaluation (NDT/NDE) ultrasound techniques with the fusion of voltage, temperature, current, sound, and gas measurements in a small low-power and low-cost embedded unit. The key innovation of this approach lies in the application of ultrasound measurement techniques using low-cost, low-power miniature ultrasonic transducers with advanced data fusion algorithms to achieve a reliable early warning fault indication system for lithium battery packs. The solution will be implemented in X-wave s SWaP embedded platform that will transfer the gathered information, either wirelessly or through a single pair of wires, to a central processing unit for analysis and safety risk level evaluation and indication. For more information on these proposals, contact Dr. Laura Xing (yxing3@calce.umd.edu) or Dr. Michael Pecht (pecht@calce.umd.edu).

6 NOVEMBER 2016 PAGE 6 Dr. Elham Sahraei from MIT visits CALCE Dr. Elham Sahraei from Impact and Crashworthiness Laboratory at Massachusetts Institute of Technology (MIT) visited CALCE on June 1, She is the co-director of Battery Modeling Consortium at MIT and has extensive experience in mechanical modeling and crashworthiness of Li-ion batteries. She presented her work on mechanical characterization of Li-ion batteries and development of computational models to simulate deformation and failure of electric vehicle batteries in case of a vehicle crash. CALCE researchers Dr. Laura Xing, Saurabh Saxena, and Lingxi Kong presented their research studies at the meeting and discussed possible areas of collaboration. CALCE is focused on battery modeling, state estimation, and battery safety and reliability. From left to right, Lingxi Kong (CALCE), Saurabh Saxena (CALCE), Dr. Elham Sahraei (MIT), Dr. Yinjiao (Laura) Xing (CALCE), Yi Wu (CALCE, NUAA China) Beijing Institute of Technology wins Chinese NSF proposal with CALCE The current battery management systems based on voltage, current, and temperature measurements and conventional models are not suitable to capture the capacity degradation mechanism of Li-ion batteries in electric vehicles. This project aims to develop a methodology for mechanical characterization of vehicle battery packages and a physics-based model for battery package design and state estimations. For more information on these proposals, contact Dr. Yinjiao (Laura) Xing (yxing3@calce.umd.edu) or Dr. Michael Pecht (pecht@calce.umd.edu).

7 CALCE BATTERY NEWSLETTER PAGE 7 Visiting Scholars Junfu Li is a research scholar at CALCE and a candidate for a doctoral degree at Harbin Institute of Technology (HIT), China. He received his bachelor s degree (2013) from the Department of Electrical Engineering at HIT. His research focus is towards creating a battery state-of-charge estimation based on a simplified mechanism model. On the subject of battery discharge capacity estimation and battery model establishment, he has published six papers in respected journals, including the Journal of Power Sources and Energy. Ms. Yi Wu is a Ph.D. candidate in the College of Automation Engineering, Nanjing University of Aeronautics and Astronautics (NUAA), China. She received a B.S. and M.S. in Measuring and Testing Technologies at NUAA, China. Her research focuses on the prognostics and health management of electronic systems and devices (power electronic systems, batteries). She has been working at CALCE since September As a visiting scholar at CALCE, her research mainly focuses on Li-ion battery failure mechanisms and modes identification using the three-electrode cell. Lab Service Projects In addition to research programs, CALCE is assisting companies with battery testing, failure investigations, and battery qualification though its Test Services and Failure Analysis activity. Recent work has includes evaluation of batteries and battery management systems being used in power tool segment. In addition to extreme temperature, the impact of vibration and shock loading on batteries has also been examined. Investigations have included x-ray of battery packages and single cells, measurement of cell and pack capacity, disassembly and inspection of anode, cathode, and separator material. Composition of internally generated gases as well as cathode, anode, and separated have also been documented. CALCE alumnus Nick Williard also studied the behavior of Li-ion batteries under external loading conditions as part of his doctoral research. CALCE has state-of-the-art facilities and equipment to conduct reliability and safety assessment of Li-ion batteries under different use conditions. For initiating a lab service project with the CALCE Battery Group, please contact Dr. Michael Osterman (osterman@calce.umd.edu) or Dr. Yinjiao(Laura) Xing (yxing3@calce.umd.edu).

8 NOVEMBER 2016 PAGE 8 Open Access to CALCE Battery Data CALCE has recently conducted a study on the effects of state of charge (SOC) ranges on lithium-ion battery degradation. The data from this study is available on CALCE Battery Database website. Access to this data is free and can be obtained by filling out a simple form on the website. The detailed description of this data can be found in the following published article: Saurabh Saxena, Christopher Hendricks, and Michael Pecht, Cycle life testing and modeling of graphite/licoo 2 cells under different state of charge ranges, Journal of Power Sources, Vol. 327, pp , CALCE Battery Database contains data from previous studies and experiments as well. The data from these tests can be used for battery state estimation, remaining useful life prediction and battery degradation modeling. CALCE has published many articles using this data. Researchers such as Dr. Zhaojun Li from the Department of Industrial Engineering and Engineering Management at Western New England University and Dr. Datong Liu from the Department of Automatic Test and Control at Harbin Institute of Technology have used CALCE battery data for their research. The cycling data has been generated using Arbin and Cadex standard battery testers. Impedance data has been collected using Idaho National Laboratory s Impedance Measurement Box (IMB). For any questions on the CALCE Battery Database, please contact Dr. Laura Xing (yxing3@calce.umd.edu). Recent CALCE Battery Publications The following are recent CALCE publications on Li-ion batteries. For more information, visit the CALCE battery website: Ximing Cheng, Liguang Yao, Yinjiao Xing, and Michael Pecht, Novel parametric circuit modeling for Li-ion batteries, Energies, Vol. 9, Issue. 7, pp , 2016, doi: /en Fangdan Zheng, Yinjiao Xing, Jiuchun Jiang, Bingxiang Sun, Jonghoon Kim, and Michael Pecht, Influence of different open circuit voltage tests on state of charge online estimation for lithium-ion batteries, Applied Energy, Vol. 183, pp , Saurabh Saxena, Christopher Hendricks, and Michael Pecht, Cycle life testing and modeling of graphite/licoo 2 cells under different state of charge ranges, Journal of Power Sources, Vol. 327, pp , Chris Hendricks, Nick Williard, Sony Mathew, and Michael Pecht, A failure modes, mechanisms, and effects analysis (FMMEA) of lithium-ion batteries, Journal of Power Sources, Vol. 297, pp , Jian Guo, Zhaojun Li, and Michael Pecht, A Bayesian approach for Li-ion battery capacity fade modeling and cycles to failure prognostics, Journal of Power Sources, Vol. 281, pp , Guangxing Bai, Pingfeng Wang, Chao Hu, and Michael Pecht, A generic model-free approach for lithiumion battery health management, Applied Energy, Vol. 135, pp , Wei He, Nick Williard, Chaochao Chen, and Michael Pecht, State of charge estimation for Li-ion batteries using neural network and unscented Kalman-based error correction, Electrical Power and Energy Systems, Vol. 62, pp , Yinjiao Xing, Wei He, Michael Pecht, and Kwok Leung Tsui, State of charge estimation of lithium-ion batteries using the open-circuit voltage at various ambient temperatures, Applied Energy, Vol. 113, pp , 2014.

9 CALCE BATTERY NEWSLETTER PAGE 9 Are you interested in getting a Ph.D. at the University of Maryland in Li-ion battery or supercapacitor technologies? The University of Maryland, College Park, has established an impressive track record in battery and supercapacitor research. The research objectives focus on developing methods and tools to prevent failures, enhance safety, and make better use of the available energy in energy storage systems. The demand for people with this expertise is now widespread in all sectors of industry, from consumer electronics to automotive and aerospace. At the University of Maryland, research has focused on a wide range of topics in battery life cycle use and management. Estimating the internal electrochemical state of the battery is required to implement effective control and monitoring algorithms. This includes developing data-driven and physics-based state-of-charge models for mission planning and state-of-health models to assess the degradation of the battery as it is used. Researchers at UMD have also developed fault detection methodologies to detect failure precursors and mitigate catastrophic failure. This requires identifying the root cause of battery failure and assessing the reliability and safety of batteries and battery packs as a function of their usage environment and stresses applied during the life cycle. Supercapacitor studies have helped to reveal the key failure modes and mechanisms in response to thermal and electrical stresses. This research is multidisciplinary, drawing from the fields of electrochemistry, reliability, mechanics, electronics, controls, and machine learning. CALCE laboratories are well equipped with the latest tools and equipment for analysis and have collaborated with national and international research centers, giving qualified students access to facilities and experts around the globe. You can find more information on battery research at CALCE at Financial support is available through research assistantships for those interested in obtaining a Ph.D. at the University of Maryland in Li-ion battery technologies. If you have obtained an M.S. with a focus on batteries, knowledge of electrochemical devices, and experience in testing and model development, please apply. Preference will be given to students with an M.S. degree in science and engineering with evidence of related skills such as: Electrochemistry and secondary battery fabrication Prognostics and health management (PHM) algorithm development Battery test equipment experience (brands such as Arbin, Cadex, Maccor) Electrochemical testing (e.g., cyclic voltammetry, GITT, PITT, impedance spectroscopy) Failure analysis (e.g., non-destructive analysis, cell disassembly, materials characterization) Multiphysics model development (e.g., COMSOL, FEA) Programming experience (e.g., MATLAB, Python, R) For additional information, please contact Prof. Michael Pecht at pecht@calce.umd.edu with a resume that provides information on relevant skills and prior experience. Information about applying to the Mechanical Engineering PhD program at UMD can be found at Join the CALCE PHM Consortium To become a member and support the CALCE Battery and PHM team, please Prof. Michael Pecht (pecht@calce.umd.edu) and we will provide you with the membership agreement. Image Courtesy of John Consoli / UMD