Pressure-Induced In Situ Lithiation of Si-Based Interlayers for Stable Li-Metal Anodes in All-Solid-State Batteries

Li metal anodes are essential for high-energy-density all-solid-state batteries (ASSBs) but suffer from dendrite growth and interfacial instability. Here, a Si@CNT interlayer is introduced to enhance interfacial contact and Li-ion transport. The Si@CNT composite, prepared via scalable spray drying, undergoes in situ lithiation during cell assembly, forming a conductive and lithiophilic Li x Si phase with an embedded carbon nanotube (CNT) network. This structure suppresses dendrite formation, mitigates electrolyte decomposition, and promotes fast Li transport. Li symmetric cells exhibit high critical current densities of 4.5 mA cm –2 at 45 °C and 8.0 mA cm –2 at 80 °C with stable cycling over 800 h. Full cells show 84% capacity retention after 200 cycles and deliver ∼171 mAh g –1 at 10C, outperforming bare Li- and Si-only references. These results demonstrate a scalable interfacial strategy for high-rate, long-life ASSBs.