Slurry mixing for fabricating silicon-composite electrodes in all-solid-state batteries with high areal capacity and cycling stability

Abstract

All-solid-state batteries comprising sulfide solid electrolytes are promising for energy storage in electric vehicles because of their safety record. There is a high demand for batteries in the form of stackable compact sheets with high cell-based energy density that are mass fabricated in a scalable process. A slurry coating is advantageous for fabricating sheet-type batteries, improves productivity, and allows control of the layer thickness. Here we present a slurry-mixing method for fabricating homogeneously dispersed composite sheets containing micrometer-sized silicon particles. Subsequent removal of the volatile binder from the stacked-sheet cells is demonstrated to reduce their internal resistance. The silicon composite sheets exhibit high initial Coulombic efficiencies of 95%, with practical areal capacities of 2.0–4.4 mAh cm−2 at the 47th cycle under 0.30 mA cm−2, a reversible specific capacity of 2300 mAh g−1 after 100 cycles, and long-term cycling stability (specific capacity above 1700 mAh g−1 after 375 cycles). Cracks that are vertical to the silicon composite layer after cycling buffer the internal strain originating from silicon volume changes, providing excellent cycling stability. These results can assist the rational design of silicon anodes for high-cell-performance all-solid-state batteries.