Numerical analysis of the cyclic mechanical damage of Li-ion battery electrode and experimental validation

Evidences have accumulated that the cyclic diffusion-induced stress within lithiation-delithiation process will result in the cyclically evolutive mechanical damage of battery electrode, which adversely affects the mechanical integrity as well as the performance of the Li-ion battery. In this work, the mechanical degradation of electrode under electrochemical-mechanical condition is innovatively evaluated as a fatigue damage process, governed by the interaction between diffusion behaviour and stress generation, and accumulated fatigue damage affected stress–strain response. Structural configuration of a layered electrode plate is modeled in finite element software ABAQUS and a set of user subroutines are developed to implement the proposed fatigue evaluation approach for battery electrode. The constructed approach is proved to be able to simulate multifarious categories of fatigue damage accumulation trends of battery electrode. The strategy to correlate the electrochemistry represented damage with mechanical fatigue damage are proposed. Experimental performance tests are conducted to parameterize the fatigue damage model within the assessment approach for electrode material LiNi_0.5Mn_0.3Co_0.2O₂ (NMC532). After parameterization, further circulating charging-discharging experiments and fatigue damage simulations with respect to different C-rate conditions are carried out to study the applicability of the proposed evaluation model as well as the assumption between electrochemical and mechanical deterioration. It is observed that the electrode surface adhering to electrolyte is more prone to fracture in the cycling operation. The present research work shows that it is available to apply the fatigue damage method to study the gradually mechanical failure of battery electrode under electrochemical-mechanical condition.