An electrochemical-mechanical synergistic regulation by constructing a double-layer fully active silicon-based alloy anode in sulfide all-solid-state batteries

Abstract

Silicon anode is one of the most promising anode materials for sulfide all-solid-state batteries (ASSBs) due to its high theoretical specific capacity of up to 4200 mAh g⁻¹. However, raw silicon anodes suffer from their intrinsic limitations, including low ionic and electronic conductivity, as well as significant mechanical stress arising from large volume changes during cycling. These factors contribute to the poor cycle life of silicon-based ASSBs. Herein, a double-layer structure composed of lithium-rich Li_4.4Si alloy layer and nano silicon (nSi) anode layer, is proposed to address these issues. The double-layer structure enriches Li_4.4Si on the current collector side, serving as conductive lithium reservoir that improves the Li⁺ transport and electron conductivity. The low elastic modulus of Li_4.4Si alleviates the mechanical stress induced by volume changes in the silicon upper layer. Finite element analysis indicates that the double-layer design reduces interfacial stress by three times, ensuring effective interfacial contact and providing abundant Li⁺ transport pathways. The ASSBs employing the double layer silicon anode coupled with LiNi_0.8Mn_0.1Co_0.1O₂ (NCM811) cathode exhibit exceptional cycle stability, achieving the capacity retention rate of 86.50 % after 200 cycles at 0.5 C. Furthermore, a remarkable cell-level energy density of 308.04 Wh kg⁻¹ was achieved at a high loading of 3.38 mAh cm⁻². The double-layer Li_4.4Si/nSi anode can be incorporated into pouch cells, demonstrating good cycling stability. This design holds significant potential for the transition of sulfide ASSBs from laboratory-scale development to industrial applications.