Effects of pressure evolution on the decrease in the capacity of lithium-ion batteries

Abstract

External mechanical pressure can affect the cycle life of lithium-ion battery. In this paper, the evolution process of the mechanical pressure that a lithium-ion battery was subjected to during approximately 3000 cycles under the fixed constraint was studied through charge-discharge cycling tests of a lithium-ion battery. The effect of external pressure on battery aging in the late cycle stage was explored through SEM and incremental capacity analysis (ICA). In addition, three groups of comparative experiments, including a rigid constraint, an elastic silicone pad constraint and a spring constraint, were set up to explore the influence of different constraint schemes on battery cycle life. The experimental results showed that the mechanical pressure increased due to the aging of the battery under the fixed constraint, which could cause the anode material of the battery to crack. In the comparative experiment, the capacity decrease rate of the spring compression constraint scheme was 5.13% and 6.17% lower than those of the other two groups. The ohmic resistance increase rate was 8.67% and 12.36% lower than those of the other two groups, and the coulombic efficiency of the spring constraint remained good in the late stage of the cycle. Therefore, the spring constraint scheme can maximize the positive effect of external pressure on lithium-ion batteries by maintaining a relatively stable external pressure. The results presented in this paper have a certain guiding significance for the design of the battery pack.