Green Design of Si/SiO₂/C Composites as High-Performance Anodes for Lithium-Ion Batteries

Si/SiO2@C anode materials have great application in lithium-ion batteries (LIBs). Herein, Si/SiO2 has been prepared by a facile method from abundant natural silica diatomite. The obtained material consists of mixed nanodomains of Si and SiO2. The Si/SiO2 has been further coated with lignin-derived carbon to prepare a Si/SiO2@C material. The as-prepared Si/SiO2@C material shows a homogeneous carbon coating with a thickness of ≈5 nm and improved cycling performance as well as rate capability compared to the Si/SiO2 material. At a commercial level, an areal capacity of ≈2.5 mAh cm–2 and a pressing density of 1.3 g cm–3, the Si/SiO2@C anode exhibits stable cycling performance with 87.1% capacity retention after 150 cycles in a half cell. In full cell configuration paired with a Li[Ni0.8Co0.1Mn0.1]O2 cathode, a prelithiation method based on the electrical shorting of the Si/SiO2@C electrode with lithium foil is introduced. The initial Coulombic efficiency of the full cell is effectively improved and reaches 85.4%, and the excellent reversibility enables robust full cell operations. After 100 cycles at 0.2 C, 91.3% capacity retention is achieved. The exceptional electrochemical performance is due to the synergistic effects of the Si/SiO2 composite nanostructure from the facile synthesis method and carbon coating from lignin. This work presents a green approach for fabricating high-performance Si/SiO2@C anodes from sustainable feedstocks, with significant application potential in LIBs.