Analysis of the lithium-ion battery capacity degradation behavior with a comprehensive mathematical model

The influence of transition metal deposition on the capacity of lithium-ion batteries (LIBs) can not be ignored. The current model lacks a comprehensive analysis of the coupling phenomenon. Based on the classic P2D model, we propose a comprehensive capacity degradation model of LIBs, with a complete description of the side effects of transition metal dissolution in the positive electrode, solid electrolyte interphase (SEI) formation, and metal deposition in the negative electrode. Simulations are implemented and compared for the evolution of the battery capacity as cycling progressed in different cases of only SEI layer growth, SEI growth couples with Li plating, SEI growth couples with Mn dissolution and deposition, and all the three factors fully couples. The capacity degradation behavior is revealed from the perspective of lithium-ion inventory, diffusion coefficient, and porosity. The results show that the plating of Li leads to a significant decrease of the lithium-ion concentration, which is the prime for the attenuation of capacity. The growth of SEI alone has little effect on the capacity, which maintains 95.9% even after 2500 cycles. Although the dissolved content of Mn is just ppm scale, it can accelerate the growth of SEI layer and thus obviously affect the battery capacity.