High yield and low-cost ball milling synthesis of nano-flake Si@SiO₂ with small crystalline grains and abundant grain boundaries as a superior anode for Li-ion batteries

A high yield and low-cost high-energy wet ball milling method is used for producing nano-flake Si@SiO₂ as an anode material for Li-ion batteries. After a two-step ball milling (coarse milling and fine milling) process, the irregular plate-like micrometric Si (average particle size is 27.4 μm) is fractured into nano-flake Si@SiO₂ (average particle size is 154.8 nm) with small crystalline grains and abundant grain boundaries. Due to the significant changes of the prepared nano-flake Si@SiO₂ in the surface composition, particle size and crystal structure, the ball milled Si shows better electrochemical performance compared with the as-received micrometric Si. And the fine milled Si shows the best electrochemical properties with a high initial coulombic efficiency of 84.6% and a specific capacity of 1920.4 mA h g^-1 at a current density of 100 mA g^-1 after 100 cycles.