Metallurgy of aluminum-inspired formation of aluminosilicate-coated nanosilicon for lithium-ion battery anode

Modification of Si anode with various coating matrixes is a promising strategy to resolve the unstable solid electrolyte interphase issues. However, the complex preparation process and inherently weak interaction between Si and other matrixes impede its practical application. Inspired by the metallurgical process of aluminum, an aluminosilicate matrix was prepared as coating layer on the surface of Si nanoparticles after heat treatment. Si nanoparticles with a uniform native oxide layer were used as seed crystals for the adsorption of aluminum hydroxide. The strong symbiosis and bond between alumina and silica, such as mullite (3Al₂O₃·2SiO₂) or kaolin (Al₂O₃·SiO₂·2H₂O), provide homogeneous and durable contact coating layer. The as-produced Si/SiO₂·Al₂O₃ composite delivers a charge capacity of 1440 mAh·g⁻¹ at 100 mA·g⁻¹ and remains 879 mAh·g⁻¹ at 3 A·g⁻¹. After 200 cycles, the capacity retention remains high at 76%. The enhanced properties were ascribed to SiO₂·Al₂O₃ synergistic composite coating layer, which could hinder the interfacial side chemical reaction and buffer volume change of Si.