Impact of state-of-charge on solid electrolyte interphase formation during the battery formation process and its electrochemical implications

초록

The formation process in lithium ion battery (LIB) manufacturing is a critical step in ensuring stable electrochemical performance and safety. This study investigates the impact of pre-charging levels, specifically state-of- charge (SOC) conditions of 20 % and 80 %, on the structural, chemical, and electrochemical properties of the solid-electrolyte interphase (SEI) layer. In this study, the formation process is applied to the 21700 type (2 Ah), one of the models of actual commercial products, to examine its effect under varying conditions. High SOC conditions during pre-charging (SOC 80 %) promote the formation of LiOH, Li2CO3, and Li2O, which negatively impact ion mobility and reduce C-rate performance, within the SEI layer, leading to excessive consumption of lithium salts and carbonate solvents. In the comparison of cycling performance, there is little difference between the two samples at room temperature. However, at a high temperature of 45 degrees C, the SOC 20 % sample demonstrates significantly better performance. These findings highlight the importance of optimizing pre-charging parameters in the formation process to balance performance, cost, and safety in LIB production.

키워드