Preparation and electrochemical performance of polymer-derived SiBCN-graphene composite as anode material for lithium ion batteries

The siliconboron carbonitride/graphene (SiBCN/GN) composites were designed and synthesized by the insertion of GN sheets into the ceramic network of polymer-derived SiBCN via liquid dispersion (SiBCN/GN-Id) and solid phase blending (SiBCN/GN-sp) at 1100 degrees C. The composites were used as anode materials in lithium-ion batteries, and their electrochemical performances were investigated. Electrochemical measurements showed that the SiBCN/GN-Id exhibited a first cycle discharge capacity of 844.2 mA h g(-1) at a current density of 80 mA g(-1), which was higher than those of SiBCN/GN-sp, SiBCN, and GN anodes. The discharge capacity reduced to 347 mA h g(-1) and remained in this range over 30 cycles. SiBCN/GN-ld anode contained Si3N4, SiC, BNC, and free carbon nanocrystals sites, and GN acted as layered base supporting the SiBCN cluster, thus resulting in improved chemical stability and chemical electronic conductivity. Therefore, the SiBCN/GN-ld showed the improved electrochemical performances that were attributed to the presence of GN. GN layers acted as the supporting layers to stabilize the SiBCN matrix and alleviate the expansion of material structure during charge discharge cycle. Dependence of the electrochemical capacities of the SiBCN/GN composites on their compositions and structures indicated the promising potential to enhance the electrochemical performances of the materials through molecular design and/or the control of the material structure.