Enhanced ion conductivity and electrode–electrolyte interphase stability of porous Si anodes enabled by silicon nitride nanocoating for high-performance Li-ion batteries

Abstract

Silicon (Si) is a promising anode material for next-generation high-energy lithium-ion batteries (LIBs) due to its high capacity. However, the large volumetric expansion, poor ion conductivity and unstable solid electrolyte interface (SEI) lead to rapid capacity fading and low rate performance. Herein, we report Si nitride (SiN) comprising stoichiometric Si3N4 and Li-active anazotic SiNx coated porous Si (p-Si@SiN) for high-performance anodes in LIBs. The ant-nest-like porous Si consisting of 3D interconnected Si nanoligaments and bicontinuous nanopores prevents pulverization and accommodates volume expansion during cycling. The Si3N4 offers mechanically protective coating to endow highly structural integrity and inhibit superfluous formation of SEI. The fast ion conducting Li3N generated in situ from lithiation of active SiNx facilitates Li ion transport. Consequently, the p-Si@SiN anode has appealing electrochemical properties such as a high capacity of 2180 mAh g−1 at 0.5 A g−1 with 84% capacity retention after 200 cycles and excellent rate capacity with discharge capacity of 721 mAh g−1 after 500 cycles at 5.0 A g−1. This work provides insights into the rational design of active/inactive nanocoating on Si-based anode materials for fast-charging and highly stable LIBs.