Cu₃Si-doped porous-silicon particles prepared by simplified chemical vapor deposition method as anode material for high-rate and long-cycle lithium-ion batteries

To provide a possible proposal for the large-scale production of a high performance silicon-based anode material in the lithium battery industry, a Cu₃Si nanoparticle doped porous-silicon particles was prepared via a simplified chemical vapor deposition (CVD) process and heat treatment for the first time. In this work, the Cu₃Si doping content was optimized by discharge/charge, transmission electron microscopy and electrochemical impedance spectroscopy tests. The results show that compared with the porous-silicon (PS) particles, the Cu₃Si doping significantly enhanced the discharge capacity, coulombic efficiency, capacity retention, and high-rate performance of the silicon-based anode. The optimum performance with a discharge capacity of 3036.4 mA h g⁻¹and a coulombic efficiency of 90.49% at the first cycle (after the first three formation cycles) and a capacity retention of 58.72% after 100 cycles occurred at a Cu₃Si doping content of 2 wt%. The reasons for this are as follows: the PS particles with a similarly silicon nanorod structure accommodated the volume change to maintain the mechanical stability of the electrode during the cycling process; during the simplified CVD process, the nanostructure of silicon was retained; the high conductivity due to Cu₃Si doping decreased the formation resistance of the solid-electrolyte interphase (SEI) film and enhanced the diffusion coefficient of Li⁺inside the silicon-based material; both fewer Cu₃Si doping and aggregation particles resulting from excessive Cu₃Si doping yielded insufficient electrical conductivity and decreased the formation resistance of the SEI film for the silicon-based material.