Building sandwich-like carbon coated Si@CNTs composites as high-performance anode materials for lithium-ion batteries

Abstract

The naturally abundant and environmentally friendly silicon (Si) with a high theoretical capacity has emerged as a promising anode material for lithium-ion batteries. However, its huge volume change upon lithiation/delithiation has destructed the structural integrity and stability, while the poor electronic/ionic conductivities have severely diminished the reaction kinetics, leading to a poor electrochemical performance of Si anode. To circumvent these challenges, the Si nanoparticles have been initially grown on CNTs through a magnesiothermic reduction of SiO2 and rationally coated by amorphous carbon via a carbonization of phenolic resin. Specifically, the carbon coating, which would not only suppress the structural collapse of Si in large volumetric variation upon cycling, but also facilitate the migrations of electrons and ions, was found to determine the electrochemical reversibility and durability of C@Si@CNTs composites. Benefitted from the significantly improved structural stability and reaction kinetics, the sandwich-like coaxial C@Si@CNTs with a desirable carbon coating would exhibit a highly stable reversible capacity of 496 mAh g−1 with a 76.8% capacity retention over 800 cycles at a current density of 500 mA g−1 and maintain a large reversible capacity of 551 mAh g−1 at a current density of 2000 mA g−1. This novel construction of C@Si@CNTs sandwich nanostructure would contribute to the research development of highly stable and durable silicon anode materials for high-energy and long-life lithium-ion batteries.