Thermal treatment modification of copper–silicon alloy anode material with carbon coating on the surface

In this paper, copper (Cu) nanoparticles is deposited on the surface of silicon (Si) particles by electroless deposition. Then the electrode is prepared by mixing the modified Si/C particles with conductive agents and adhesives. Finally, rapid thermal process (RTP) is used to treat the electrode, so that interfacial Cu–Si alloyed and uniform carbon-coated Si anode materials (Si/Cu₃Si/Cu@C) are obtained by one step. The reversible specific capacity remains 1362 mAh g⁻¹ after 100 cycles at 0.2 C (1 C = 4.2 A g⁻¹), which is 997 mAh g⁻¹ higher than that of Si electrode. Through the multiplier test, the specific capacity of Si/Cu₃Si/Cu@C holds on 604 mAh g⁻¹ at 2 C. The excellent electrochemical performance of Si/Cu₃Si/Cu@C composite materials is mainly attributed to the dual buffering media of nano-copper particles and carbon layers. Firstly, the presence of copper particles on the silicon surface can improve the overall conductivity and the volume expansion coefficient of silicon, thereby overcoming the rapid capacity decay of the electrode caused by excessive resistance. Secondly, the surface carbon layer can further alleviate the mechanical stress during the lithium intercalation and deintercalation process, effectively isolate the active material from the current collector, and ensure good electrical contact of the active particles and the stability of the surface SEI film.