Reversible Nano Crystalline-Phase Transformation in Si-Based Anode Enables Stable All-Solid-State Batteries

Sulfide-based all-solid-state batteries employing Si anodes hold great promise for achieving high safety and energy density. However, the severe structural degradation of Si during cycling and its sluggish reaction kinetics lead to rapid capacity decay, significantly limiting battery lifespan. Herein, we propose a reversible nanocrystalline-phase transformation strategy by incorporating phosphate (P) and zinc (Zn) into a Si matrix to develop a high-capacity and stable Si-based anode. The anodes are electrochemically driven and converted <i>in situ</i> into Li₁₅Si₄, LiZn, and Li₃P nanocrystalline phases during cycling, which mitigated the expansion stress of the electrode, maintaining its structural stability. Meanwhile, Zn and P reduced the Li-ion diffusion energy barrier and band gap of Si, improving the ion/electron transport ability within the electrode. The NCM90-based full cell incorporating this anode demonstrates stable operation for over 3,000 cycles at 2C rate. This alloy-based anode design offers an effective pathway for developing long-cycle-life all-solid-state batteries.