Effect of Si content on structure and electrochemical performance of ternary nanohybrids integrating Si nanoparticles, N-doped carbon shell, and nitrogen-doped graphene

Abstract

Hybridizing graphene with silicon (Si) is effective in developing high-performance Si-based anodes. However, the effect of Si content on the structure and electrochemical performance of these nanohybrids has not been extensively studied. Herein, a type of ternary Si/NC/NG nanohybrid with varying Si content was synthesized via a scalable, ecofriendly, and facile solution-mixing and carbonization process. In this nanostructure, Si nanoparticles were sheathed with N-doped carbon (NC) and the NC-wrapped Si nanoparticles were confined by nitrogen (N)-doped graphene (NG). The focus of this work was to determine how the Si content in the ternary nanohybrid affects its structure and electrochemical performance. SEM and TEM observations revealed that all Si nanoparticles were embedded in graphene nanosheets at low Si content while some aggregated and bare Si nanoparticles were observed at high Si content. Despite the simple preparation procedure, the ternary nanohybrid with an optimal Si content (83.9 wt%) delivered a high reversible capacity of 1210 mA h g⁻¹ after 100 cycles at 0.5 A g⁻¹, which outperforms most Si-based anodes in lithium-ion batteries (LIBs) reported so far. The findings presented in this paper represent a new criterion for the design of Si-based anodes with optimized electrochemical performance.