关键词: 锂离子电池, 老化特性, 快充, 电化学-热-力耦合模型

Abstract: This paper numerically investigates the aging characteristics of lithium-ion battery (LIB) under fast charging based on an electrochemical-thermal-mechanical (ETM) coupling model. First, the ETM coupling model is established and solved by COMSOL Multiphysics. Subsequently, a long cycle test is conducted to explore the aging characteristics of LIB. Specifically, the effects of increasing C rates and number of cycles on battery aging are analyzed in terms of non-uniform distribution of solid electrolyte interface (SEI), SEI formation, thermal stability and stress characteristics. The results indicate that the increase in C rates and cycling leads to an increase in the degree of non-uniform distribution of SEI, as well as a consequent increase in the capacity loss due to SEI formation. Meanwhile, the increase in C rates and the number of cycles 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.

Key words: lithium-ion battery, aging characteristics, fast charging, electrochemical-thermal-mechanical coupling model