Preparation and improved electrochemical performance of SiCN–graphene composite derived from poly(silylcarbondiimide) as Li-ion battery anode

Abstract

A SiCN–graphene nanocomposite anode material is designed and synthesized by the insertion of graphene sheets into the ceramic network of silicon carbonitride for the development of structurally and electrochemically stable lithium ion batteries. SiCN–graphene composite synthesis was achieved through controlled pyrolysis of poly(silylcarbondiimide)-derived SiCN on graphene surfaces that resulted in formation of a graphene supported ceramic SiCN–graphene architecture, in which graphene works as the layered base supporting the SiCN clusters. SiCN–graphene anode showed a stable charge–discharge capacity of 475.1 mA h g⁻¹ after 100 cycles at a current density of 40 mA g⁻¹, which is 6.2 times that of bare SiCN anode (76.1 mA h g⁻¹). The average coulombic efficiency (excluding the first cycle loss) was 97.93%. Moreover, SiCN–graphene anode showed improved high-rate capability. At 2 C rate (a current density of 800 mA g⁻¹), the capacity of SiCN–graphene was above 260 mA h g⁻¹, while the bare SiCN was observed to be only 2.3 mA h g⁻¹ at the same charge–discharge condition. Improved electrochemical performances of SiCN–graphene are attributed to the presence of graphene which works as the supporting layers to stabilize the SiCN matrix and alleviate the expansion of material structure during charge–discharge cycling.