Investigation on high-energy Si anode mechanical-electrochemical-thermal characteristic under wide temperature range

Studying the cyclic evolution of high-energy Si anode, including the mechanical deformation, voltage hysteresis, heat generation and temperature response, is of great significance for its performance and safety. In this paper, a novel coupled semi-analytical model is developed to investigate the mechanical-electrochemical-thermal characteristic of Si particle anode. This model is adopted a series of temperature and concentration dependent parameters related to electrochemical reaction and Li⁺ diffusion. The results show that Li⁺ diffusion process will be limited at a lower initial temperature, which may increase the elastic–plastic stress. Thus, the stress-induced voltage hysteresis is more evident, resulting in the capacity loss and polarization heat increase. In the aspect of thermal behavior, the heat generation during lithiation is more than that during delithiation at each initial temperature, and the total heat accumulation after one cycle is greater at a higher initial temperature. Besides, the asymmetrical elastic–plastic deformation and heat accumulation during cyclic lithiation/delithiation may lead to ratcheting deformation of the Si particle electrode. The ratcheting deformation will be aggravated at a lower temperature. Additionally, the effects of charging rates (0.2C, 0.5C and 1C) are also discussed. The increased charging rate leads to a steeper concentration gradient, the more obvious asymmetrical elastic–plastic deformation, and earlier reaching the cut-off voltage. The electrode will produce more heat in a short time in the case of fast charging, and the resulting self-heating accumulation will affect its thermal stability. Based on this, ratcheting deformation at a fast charging rate is more severe, which will further decrease the mechanical stability of the Si electrode. The theoretical results are verified by the experiments. This study provides a theoretical and experimental basis for understanding the comprehensive performance of high-energy lithium-ion batteries, as well as design and management guidance.