Accounting for Non-Ideal, Lithiation-Based Active Material Volume Change in Mechano-Electrochemical Pouch Cell Simulation

Automotive battery manufacturers are working to improve individual cell and overall pack design by increasing their safety, performance, durability, and range, while reducing cost; and active material volume change is one of the more complex aspects that needs to be considered during this process. In the study shown here, thermodynamically non-ideal, lithiation-based volume change behavior for the anode and cathode active materials were incorporated into a previously developed mechano-electrochemical model. The changing thickness of an automotive-relevant, large-format pouch cell was predicted while simulating cell discharge. Measurements were taken using an experimental setup capable of simultaneous mechanical and electrochemical operation and observation. The electrochemical and mechanical measurements prove to agree well with simulation when using non-ideal lithiation-based volume change as opposed to the previously assumed ideal volume change behavior. The resulting model was used to simulate other mechano-electrochemical phenomena including the effects of anode/cathode capacity ratio and changing pressure/porosity during cell discharge. This mechano-electrochemical model shows promise to help define operational parameters to mitigate negative effects from active material volume change and may act as a tool for developers reduce the extensive electrochemical and mechanical testing required for the design of promising new batteries.