Aging Characteristics of Lithium-ion Battery under Fast Charging Based on Electrochemical-thermal-mechanical Coupling Model

The aging characteristics of lithium-ion battery (LIB) under fast charging is investigated based on an electrochemical-thermal-mechanical (ETM) coupling model. Firstly, the ETM coupling model is established by COMSOL Multiphysics. Subsequently, a long cycle test was conducted to explore the aging characteristics of LIB. Specifically, the effects of charging (C) rate and cycle number on battery aging are analyzed in terms of nonuniform distribution of solid electrolyte interface (SEI), SEI formation, thermal stability and stress characteristics. The results indicate that the increases in C rate and cycling led to an increase in the degree of nonuniform distribution of SEI, and thus a consequent increase in the capacity loss due to the SEI formation. Meanwhile, the increases in C rate and cycle number also led to an increase in the heat generation and a decrease in the heat dissipation rate of the battery, respectively, which result in a decrease in the thermal stability of the electrode materials. In addition, the von Mises stress of the positive electrode material is higher than that of the negative electrode material as the cycling proceeds, with the positive electrode material exhibiting tensile deformation and the negative electrode material exhibiting compressive deformation. The available lithium ion concentration of the positive electrode is lower than that of the negative electrode, proving that the tensile-type fracture occurring in the positive material under long cycling dominated the capacity loss process. The aforementioned studies are helpful for researchers to further explore the aging behavior of LIB under fast charging and take corresponding preventive measures.