Monolithic 100% Silicon Wafer Anode for All-Solid-State Batteries Achieving High Areal Capacity at Room Temperature

Silicon is an attractive anode material for all-solid-state batteries (ASSBs) because it has a high energy density and is safer than metallic lithium. Conventional silicon powder composite electrodes have significant internal voids and detrimental interfaces that suppress the lithium transport and lifetime. Here, we demonstrate that surface-treated thin silicon wafers could serve as monolithic additive-free, electrolyte-free, and void-free electrodes that can achieve high areal capacity at room temperature (∼25 °C). A dense solid electrolyte interface could effectively suppress the cracks and pulverization found in the liquid electrolyte. We demonstrated that the grooved <110> wafer exhibited reversible (de)lithiation owing to fast lithium distribution along the <110> thickness direction. The surface groove could effectively penetrate the electrolyte layer, yielding a stable interfacial resistance and homogeneous alloying/dealloying processes during cycling. Our silicon wafer electrode achieved an areal capacity of 10 mAh cm–2 at room temperature, which can be improved by further optimization.