Dual carbon boosts silicon-based anodes for excellent initial coulombic efficiency and cycling stability of lithium-ion batteries

Abstract

Benefiting from its ultrahigh theoretical capacity and abundant resources, silicon (Si) is considered a prospective anode material. However, Si faces great challenges in practical applications, such as low initial coulombic efficiency (ICE) and rapid capacity decay. Herein, a silicon/graphite/reduced graphene oxide (Si/Gt/RGO) composite was prepared by agitation, freeze-drying, and heat treatment, where Si nanoparticles were embedded in a graphite (Gt) matrix and tightly wrapped by reduced graphene oxide (RGO). Graphite can promote ICE, improve lithium-ion (Li+) transport kinetics, and serve as the matrix to mitigate the swelling of Si. RGO further ensures rapid Li+ diffusion and forms a flexible shell of Si nanoparticles. The flexible shell formed by RGO can relieve internal stress and increase the tolerance of Si swelling. The dual carbon (graphite and RGO) protects Si nanoparticles from pulverization and ensures the electronic contact of Si, thereby rendering superior electrochemical properties. Si/Gt/RGO shows an excellent ICE (81.54 %), a promoted cycling stability (1007.0 mAh g−1 at 0.2 A g−1 after 100 cycles with capacity retentions of 91 % and 686.3 mAh g−1 after 200 cycles at 1 A g−1) and an outstanding rate capability (475.8 mAh g−1 at 3 A g−1). The research provides a methodology for simultaneously enhancing the ICE and cycling properties of silicon-based (Si-based) anodes and provides an idea for the rational design of LIB anodes with high- energy- density.