Synergy of Si, Sn, and SWCNT Enables a Superior Mixed-Conductive Slurry-Coated Anode for All-Solid-State Lithium Batteries

All-solid-state lithium batteries (ASSLBs) with sulfide electrolytes and high-capacity alloy anodes are among the most promising technologies for achieving high safety and energy density. Herein, we demonstrate a slurry-coated sheet-type electrode consisting of a 99.8 wt % Si–Sn hybrid active material and a 0.2 wt % single-walled carbon nanotube (SWCNT) binder, which could be used as a superior anode in ASSLBs. Compared to the typical composite powder electrode, the sheet-type Si–Sn electrode is free of electrolytes and extra carbon additives, enabling higher energy density at the electrode level but dominantly depending on Li⁺ diffusion and electron transport within the Si–Sn active material. It is identified that the lithiated Si–Sn hybrid is an excellent mixed ion-electron conductor that overcomes insufficient electronic or ionic conductivities of lithiated Si and Sn individuals. In addition, using SWCNT instead of ordinary polymer binders can improve electrode integrity and preserve electrical connections during cycling. When paired with a LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode (a mass loading of 11.3 mg cm^–2), the Si–Sn–SWCNT||NCM811 full cell shows stable cycling for more than 200 cycles at 0.5C with a capacity retention of 85.9%. Even at a high NCM811 loading of 36.4 mg cm^–2, the full cell exhibits a considerable capacity retention of 85.0% (50 cycles, 0.1C) and a maximum areal capacity of 5.8 mAh cm^–2. This work provides an industry-compatible method to produce high-performance alloy anodes for ASSLBs.