Influence of mechanochemical reactions between Si and solid electrolytes in the negative electrode on the performance of all-solid-state lithium-ion batteries

All-solid-state lithium-ion batteries that employ Si negative electrodes are the most promising candidates for next-generation batteries because of their high safety performance and energy density. However, the contact between Si and the solid electrolyte becomes insufficient because of the volume changes of Si associated with charging and discharging, resulting in a significant drop in battery performance. Although mechanical milling forms good interparticle contacts, the reaction between Si and a sulfide solid electrolyte increases the resistance, thereby decreasing battery performance. Therefore, in this study, we investigated the effects of the mechanochemical reactions between several solid electrolytes and Si on battery performance. A decrease in electronic conductivity was observed from the reaction between Si and sulfide or oxide solid electrolytes, whereas no significant decrease was observed with halide solid electrolytes. Consequently, an Si composite electrode constructed with a halide solid electrolyte showed high reversibility, achieving a high area capacity of 4.6 mA h cm−2 and specific energy density of 470 Wh kg−1 (masses of positive and negative composite electrodes) in a full-battery cell with an Li2S positive composite electrode at 0.25 mA cm−2 and 25 °C. The study contributes to understanding the important factors in the advancement of all-solid-state lithium-ion batteries. •The mechanochemical reactivity with Si varies depending on the SE species.•Si is reacted with Sulfide and oxide SE and decreased electronic conductivity.•The halide SE do not react with Si and maintain electrochemical properties.•Excellent initial reversibility by suppressing the reaction between Si and SE.•The Li2S/Si full battery cell exhibits 4.6 mA h cm−2 and 470 Wh kg−1 (electrodes).