Facile Synthesis of Double-Layer-Constrained Micron-Sized Porous Si/SiO₂/C Composites for Lithium-Ion Battery Anodes

Advanced Si-based anode materials with nano-sized porous structures and constrained coating layers present attractive prospects for lithium-ion batteries. A brand-new design of double-layer-constrained micron-sized (>20 μm) porous Si/SiO₂/C is proposed through facile synthesis processes using cheap Al-Si alloy as feedstock. The three-dimensional spherical coral-like porous Si structure is composed of primary Si (as a supporting framework), eutectic Si rods, and uniformly distributed conductive element Al, which is beneficial for providing void space and uniformly conductive sites. A 4 nm SiO₂ thin layer is introduced on the surface of porous Si structure using preoxidation treatment, which has the effect to constrain the volume expansion of Si. The outer C layer can further improve the electrical conductivity and structural stability. The discharge and charge capacities of the porous Si1/SiO₂/C composite are 933.3 and 929.2 mAh/g at 0.1 A/g after 100 cycles, respectively. The charge attenuation rate of porous Si1/SiO₂/C in each loop is only 0.08%, and the lithium-ion diffusion coefficient of this composite is 4.20 × 10^-12 cm²·s^-1/2.