A Reformulation of the Pseudo2D Battery Model Coupling Large Electrochemical-Mechanical Deformations at Particle and Electrode Levels

Abstract

The Pseudo2D electrochemical reaction/transport battery model is consistently reformulated based on the finite strain theory to incorporate the coupled effects of large electrochemical-mechanical deformations at both particle and electrode levels. The active material volume change due to lithium insertion/extraction causes the electrode deformation and porosity variation. The porosity variation affects the mechanical properties of each component of the cell as well as the transport processes. In turn, the electrode deformation also affects porosity variation and the electrochemical processes (transport and equilibrium potential). Variables such as particle size and specific surface area are also simultaneous updated based on the approximated electrode deformation and porosity distributions. The model is applied to simulate the performance of a cell composed of Si anode and NMC532 cathode to study the effect of active material volume change on the cell performances. The simulation results show that during the charging process the porosity of each cell component experiences significant reduction due to the large expansion of Si particles.Also, a notable hydrostatic stress develops within the cell, which introduces an overpotential in addition to that caused by porosity reduction. The model is also employed to study the effects of charging rate, initial anode porosity, cell loading and fixture condition.