Synergetic effect of double-layer coating on silicon nanoparticles for high-performance lithium-ion battery anodes

Abstract

Silicon has emerged as a potential candidate for next-generation lithium-ion battery (LIB) anodes owing to its exceptionally high theoretical capacity (3580 mAh g−1) and environmental abundance. However, the practical application of Si anodes is severely hindered by low electrical conductivity and a substantial volume expansion rate of over 300 % during the lithiation–delithiation process, leading to rapid capacity degradation. To address these challenges, a double-layer coating strategy was developed and successfully applied to simultaneously enhance the electrical conductivity and mechanical integrity of Si nanoparticles (Si). The double coating layer was designed with an inside conductive pathway and outside robust coverage, which was achieved by encapsulating silicon with a conductive amorphous carbon layer on the silicon surface and coating it with a TiO2 layer (Si@C@TiO₂). These features improved the interfacial and structural stability of the electrodes during repeated cycling. Compared with its respective uncoated and single-coated analogous anodes, the Si, carbon-coated Si (Si@C), and TiO2-coated Si (Si@TiO2) anodes, the Si@C@TiO₂ anode demonstrates exceptional cycling stability and power capability. We believe that this study offers a breakthrough in the design of high-performance Si-based anodes for LIBs.