Self-healing Si anodes with robust ionic and electronic conducting network by Ga-In-Sn liquid metal alloy in solid-state batteries

Solid state batteries (SSBs) with Si anodes have emerged as a promising battery system due to their high energy density and inherent safety compared to Li-ion batteries (LIBs) employing liquid electrolytes. However, there are critical challenges caused by deficient ionic and electronic conducting pathways and contact losses in Si anodes associated with severe volume changes, resulting in poor electrochemical performances. In this study, Ga-In-Sn liquid metal alloy (GIS-LMA) is introduced to achieve well-networked ionic and electronic conducting pathways within micron-sized Si (μSi) anodes in SSBs. The GIS-LMA easily infiltrates μSi anodes by replenishing the pores and then solidifies by forming alloy phases with Li during the lithiation process. The GIS-LMA in μSi anodes exhibits reversible solid-liquid phase transition and replenishes the cracks generated during cycling, showing the self-healing property of μSi anodes in SSBs. The GIS-LMA provides ionic and electronic conducting pathways and mitigates the volumetric stress associated with μSi during cycling. With those benefits, the μSi anodes with the GIS-LMA effectively heal the cracks caused by μSi volume changes associated with Li and reduce internal resistance up to 72.4 % compared to the benign μSi anodes. We demonstrate the highly reversible electrochemical reaction of μSi anodes in SSBs.