A N-doped carbon-coated porous Si–Cu composite as a high-performance anode for lithium-ion batteries†

The poor cycling stability caused by the volumetric expansion of silicon severely limits its application as an anode material for lithium-ion batteries. To address these challenges, this study developed Si/Cu@NC composites using a high-energy ball milling method combined with thermal treatment. During the thermal process, the generated silicon–copper alloy does not participate in the electrochemical reactions but acts as a supporting structure to ensure the structural integrity of the composite material. More importantly, silicon nanoparticles embedded in the pore structures formed by copper particles effectively mitigate the stress damage caused by the volumetric expansion of silicon. Additionally, the nitrogen-doped carbon layer introduces more active sites on the surface, facilitating lithium-ion insertion and extraction, thereby enhancing electrochemical activity and improving specific capacity. As a result, the Si/Cu@NC composite exhibits a specific capacity of 1045.6 mA h g⁻¹ after 800 cycles at a current density of 1 A g⁻¹, with an initial coulombic efficiency of 92.6%. The excellent performance is attributed to the porous carbon-coated structure supported by the alloy. This simple, green, and environmentally friendly method provides a new approach for fabricating other alloy-type Si–C anodes.