Preparation and properties of porous silicon anode coated with nitrogen-doped carbon for lithium ion battery

Abstract Silicon (Si) anode is a promising anode material for lithium ion batteries as its high theoretical specific capacity. However, the commercial application of Si anode faces significant challenges, primarily stemming from its substantial volume change (> 300) and associated high costs. In this work, porous silicon was prepared by etching low-cost micron-sized aluminum-silicon alloy with hydrochloric acid. Subsequently, carbon-coating the porous silicon through the pyrolysis of phenolic resin, prepare a carbon-coated porous silicon-carbon (Si/C) anode material. This process is not only characterized by its simplicity and cost-effectiveness, but the porous Si/C anode structure relieves the mechanical stress of the material and inhibits the expansion, powdering of silicon and the erosion of the electrolyte. The results show that the Si/C anode sintered at 800°C exhibits optimal performance. Specifically, the Si/C anode material presented a first discharge specific capacity of 1394.4 mAh/g, with a capacity retention rate of 46.1% at 0.5 A/g. Nitrogen-doped silicon carbon composite material (Si/NC) was synthesized to further improve the performance of Si/C anodes. The characterizations confirm good crystallinity, uniform carbon coating on silicon surfaces, and even distribution of Si, C, and N elements. The Si/NC anode achieves a first specific capacity of 1218.3 mAh/g at 0.5 A/g, with a specific capacity of 563.7 mAh/g after 300 cycles, and the cycle retention rate still remains 42.7%, demonstrating stable cycling of the micron-sized silicon anode.