Advanced Automotive Battery Conferences

Session 4B:
 

Life Test and Simulation

Mark Verbrugge is the Director of GM’s Chemical and Materials Systems Laboratory, which maintains global research programs—enabled by the disciplines of chemistry, physics, and materials science—and targets the advanced development of structural subsystems, energy storage and conversion devices, and various technologies associated with fuels, lubricants, and emissions.
Mark is a Board Member of the United States Automotive Materials Partnership LLC and the United States Advanced Battery Consortium LLC. Mark has received a number of GM internal awards as well as external awards including the Norman Hackerman Young Author Award and the Energy Technology Award from the Electrochemical Society, and the Lifetime Achievement Award from the United States Council for Automotive Research. Mark is a Fellow of the Electrochemical Society and a member of the National Academy of Engineering.

1. Life Considerations for Lithiated Silicon Electrodes
   Mark Verbrugge, Director Chemical and Materials Systems Laboratory, General Motors
   

   Coupled mechanical-chemical degradation of electrodes upon charging and discharging has been recognized as a major failure mechanism in lithium ion batteries. The instability of commonly employed electrolytes results in solid electrolyte interphase (SEI) formation. Although the SEI layer is necessary, as it passivates the electrode-electrolyte interface from further solvent decomposition, SEI formation consumes lithium and thus contributes to irreversible capacity loss. While lithiated silicon shows great promise in terms of enabling high specific energy cells, its large volume change during operation poses life challenges associated with breakage of the protective SEI. Unraveling how the system operates and what mitigation strategies might be employed to increase lifetime begins with an understanding of the governing thermodynamics, to be emphasized in this talk, after which we overview unresolved questions.
2. High-Precision Battery Testing
   Alvaro Masias, Research Engineer, Ford Motor Company
   

   Batteries are an important part of all electrified vehicles. The research and development of new battery technologies is a time consuming process, spanning several years. High precision battery testing as an approach to accelerate the validation of performance over time is an active field of research. Efforts to build a high precision, high current battery tester will be described. This work is partially sponsored through a cooperative agreement with the Department of Energy's ARPA-E Office.
3. Battery Life Modeling – Prediction vs. Results
   Eric Dufek, Energy Storage Group Lead, Idaho National Laboratory
   

   The U.S. Advanced Battery Consortium (USABC) has established performance targets for various automotive platforms including hybrid, plug-in hybrid, and electric vehicle modes. A 15-year calendar-life capability at a given reference temperature is typically included as part of these targets, thus necessitating the need for accelerated aging protocols to screen candidate technologies. Accelerated aging typically consists of calendar-life testing at elevated temperatures to increase degradation rates. From the acquired data, and a given life model, battery life estimations are conducted at the reference temperature and compared with the 15-year target. The Idaho National Laboratory has been calendar-life aging a set of lithium-ion cells at various temperatures for several years based on the USABC Hybrid Electric Vehicle (HEV) Power Assist targets. This presentation will show calendar-life estimations at various levels of battery degradation compared with the actual measured results. This work was prepared as an account of work sponsored by an agency of the United States Government under US DOE Contract DE-AC07-05ID14517.

   • Review accelerated aging protocols
   • Review battery life estimation methodology (models / statistical analysis, etc.)
   • Compare battery life prediction with measured data at various levels of battery degradation
   • Address key questions:
     • How accurate is the life model at given levels of battery degradation?
     • How long should aging be conducted to improve accuracy of the estimation?
      
   • Summary / Conclusion
4. Lifetime Prediction and Real-time Control through Modeling of Electrochemical-Thermal-Mechanical Degradation Mechanisms
   Kandler Smith, Senior Researcher, Energy-Storage Group, National Renewable Energy Laboratory
   

   It remains an open question how best to predict real-world battery lifetime based on accelerated calendar and cycle aging data from the laboratory. Multiple degradation mechanisms due to (electro)chemical, thermal, and mechanical coupled phenomena influence Li-ion battery lifetime, each with different dependence on time, cycling and thermal environment. The standardization of life predictive models would benefit the industry by reducing test time and streamlining development of system controls.

   This paper describes:

   • A generalized prognostic framework incorporating multiple degradation mechanisms from the electrochemical literature
   • Regression of the model to cell aging data and diagnosis of degradation mechanisms
   • Applications of life prognostics in real-time control
     • Heterogeneous cell control using Utah State cell power balancing hardware enabling >20% life extension in PHEVs and >40% in BEVs
     • Prognostic-based supervisory control for Eaton commercial HEV enabling 50% downsized battery
      
   • Ongoing research seeking better understanding of electrochemical-mechanical coupled degradation