Al-doping stabilized cubic SiP with metallic conductivity toward superior Li-storage performance of Li-ion batteries

Sphalerite SiP exhibits metallic properties, making it more promising than individual silicon and phosphorus for high-performance Li-ion batteries. However, due to its positive formation energy, cubic phase SiP is thermodynamically unstable at room temperature and pressure. We synthesize a cation-disordered AlSiP₂ compound with a zinc blende structure by introducing highly conductive and reactive aluminum into stable layered SiP, triggering a phase transition to form the cubic phase. This is achieved through a high-energy ball milling technique, thoroughly mixing phosphorus, aluminum, and layered SiP. Introducing aluminum turns the formation energy negative, stabilizing metallic SiP through increased structural entropy. Experimental and theoretical results show that AlSiP₂ enhances reaction kinetics and structural flexibility, providing superior lithium storage performance. The AlSiP₂-based electrode demonstrates a reversible capacity of up to 1530 mA h g⁻¹ with an initial Coulombic efficiency of 91 % at 100 mA g⁻¹. After 700 cycles at 4000 mA g⁻¹, the capacity remains at 730 mA h g⁻¹, with a capacity retention of 88.4 %. Additionally, the LiNi_0.5Co_0.2Mn_0.3O₂//AlSiP₂@C full cell cycles over 50 times without significant capacity decay, indicating practical applicability. Doping with a hetero-element to increase configurational entropy presents a promising strategy for advanced energy storage applications.