Polyborosilazane derived ceramics - Nitrogen sulfur dual doped graphene nanocomposite anode for enhanced lithium ion batteries

Silicon boron carbon nitride ceramic nanocomposites filled with nitrogen sulfur dual-doped graphene sheets (SiBCN/NSGs) were designed and synthesized by inserting pyrolyzed NSGs into the polymer derived SiBCN via ball ball milling technique and their feasibility to serve as lithium ion battery anode was tested. The insertion of NSGs in SiBCN caused extrinsic defects and more active sites, both increased the lithiation and anode stability. The resulting material significantly improved the Li-ion loading capacity and gave a higher rate ability. The high cycling performances were attributed to the stacked graphene sheets of NSGs and increased disordered carbon sites (amorphous structure), such as rearrangement of -sp² carbon chains and formation of B(C)N domains of polymer derived ceramic (PDC). The NSGs generated extrinsic defects and more active sites, hence promoted the electrode performance. The nanocomposites exhibited a reversible capacity of 785 mAh g⁻¹ even at a high current density of 450 mA g⁻¹ over 800 cycles, representing a high retained capacity of ∼780 mAh g⁻¹ with an average decay of 0.006% per cycle. Furthermore, the SiBCN anode revealed a charge capacity of 365 mAh g⁻¹ at 450 mA g⁻¹ after 500 cycles, indicating that both the assembled anodes have potential practical applications in lithium-ion batteries.