Analysis of cyclic failure in high-specific-energy Li-rich Si/C pouch batteries

Capacity decay, performance decline, and other degradations experienced by lithium-rich silicon/carbon pouch batteries during repeated charging and discharging processes are collectively called cyclic failures. These failures prevent the batteries from meeting long-term usage requirements. This study aims to effectively address these deficiencies. First, experiments were conducted on Ah-rated full batteries assembled with Li-rich manganese-based positive electrode materials and silicon/carbon negative electrode materials to examine their electrochemical properties. Second, batteries subjected to cycling were disassembled for various testing analyses to investigate the failure process of high-specific-energy Li-rich Si/C pouch batteries. The research results identify three main reasons for the capacity degradation of Ah-rated full batteries: lithium loss, electrochemical polarization, and structural damage to the negative electrode. Batteries disassembled after less than 50 cycles show slight changes in the structure of their positive and negative electrodes, as well as in elements revealed by ICP testing. This suggests that the capacity decay of these full batteries during the first 50 cycles is mainly caused by lithium loss and electrochemical polarization. Beyond 50 cycles, the capacity of the positive electrode materials decreased by 8%, while that of the negative electrode materials decreased by 70%. This indicates that, beyond this point, capacity decay in these full batteries is mainly caused by structural damage to their negative electrodes.