A Mechano-Electrochemical Battery Model that Accounts for Preferential Lithiation Inside Blended Silicon Graphite (Si/C) Anodes

Abstract

Automotive manufacturers are currently working to produce commercially-viable electric trucks, driving the need to develop batteries that are higher in energy density and lower in cost. To realize this, cell designers have introduced blended silicon-graphite anodes to combine the high energy density of silicon with the stability and relatively lower mechanical degradation of graphite. As more blended anodes with high lithiation-based volume change are considered, the need to simultaneously account for mechanical and electrochemical phenomena increases. In this study, the focus is to learn how preferential lithiation (caused by differing equilibrium potentials and other intercalation kinetics of the two blended active materials) impact the coupled electrochemical performance and mechanical phenomenon at the electrode and cell scales. To do this, adaptations of previous modeling methods are proposed that treat the active materials as separate particles, representing the mixing of two active materials powders within a slurry. For comparison, the historically-used assumption is shown, where the blended active materials lithiate uniformly. The resulting simulations show that preferential lithiation of the blended materials will have a significant impact on both electrochemical and mechanical phenomena. Discussion is also provided with regard to C-rate, blended electrode composition, and other mechano-electrochemical behavior.