Cu₃Si enhanced crystallinity and dopamine derived nitrogen doping into carbon coated micron-sized Si/Cu₃Si as anode material in lithium-ion batteries

A chemical vapor decomposition (CVD) enhanced carbon coated Si/Cu₃Si composite aggregate (C-Si/Cu₃Si@C) is prepared as anode material to alleviate volume expansion and improve the electrochemical performance for lithium-ion batteries (LIBs). In this work, micron-sized C-Si/Cu₃Si@C is fabricated through self-assembling of dopamine as first carbon precursor on irregularly shaped and sub-micron-sized Si/Cu₃Si composite, followed by CVD with ethylene (C₂H₄) as second carbon precursor. Besides, dopamine not only self-assembles on the surface of Si/Cu₃Si composite but also grows into sheet-like film that supports and connects Si/Cu₃Si composite into micron-sized aggregate. In addition to CVD, Cu₃Si induces catalytic chemical vapor deposition (CCVD), which enhances integrality of the carbon shell as well as reinforce nitrogen doping into carbon shell to enhance conductivity. Therefore, the C-Si/Cu₃Si@C composite performs in optimum condition when the cycle is stable, attaining delithiation capacity of 2101 mAh g⁻¹, coulombic efficiency of 84.7% for the 1st cycle and achieves capacity retention of 82.9% after 100 cycles.