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

Silicon (Si) is a promising anode material for next-generation lithium-ion batteries (LIBs) with its high theoretical specific capacity (4200 mAh/g). However, Si anode has a huge volume change rate (> 300%) and high cost compared to graphite, which limits the commercial application of Si anode. Carbon coating can effectively tackle the volume change and poor conductivity during cycling of Si anode. In this work, aluminum–silicon alloy was firstly etched by hydrochloric acid. Followed by a mixture with pyrolysis of phenolic resin, the carbon layer outside the silicon particles was deposited during heat treatment process. The carbon-coated porous silicon-carbon (Si/C) anode material demonstrates excellent electrochemical performance and porous structure, which relieves mechanical stress and inhibits volume expansion. The results show that Si/C present well electrochemical performance at a sintering temperature of 800 ℃. Specially, the Si/C anode delivers a high specific capacity of 1394.4 mAh/g at the current density of 0.5 A/g with 46.1% retention. 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. Simultaneously, a highly stable reversible capacity of 1218.3 mAh/g with 42.7% retention over 300 cycles at a current density of 0.5 A/g was obtained. This research can provide an alternative approach for high-energy and low-cost silicon-based anodes for LIBs.