Silicon Nanoparticles Wrapped in a Double-Layer Coating of Chitin-Derived Nitrogen-Doped Carbon Nanosheet and Pitch-Based Carbon Enabling Efficient Lithium Storage

Silicon anode is considered to be the next-generation anode material due to its high specific capacity. However, its commercial application has been hindered by the significant volume expansion during charging and discharging as well as its low conductivity. In this study, we successfully synthesized carbon-silicon composites by double-layer coating silicon nanoparticles with pitch-based carbon and N-doped carbon nanosheets. The conductive network formed by N-doped carbon nanosheets enhances the e(-)/Li+ transport capacity of the material, and the pitch-based carbon can enhance the bonding of Si and CNSs while avoiding the direct contact of Si with the electrolyte. Thus, the double-layer coating structure not only alleviates the mechanical stress caused by the volume expansion of the active material but also enhances the transport capacity of electrons and lithium ions within the composite. This leads to the creation of additional active sites for lithium storage and an overall enhancement of the electrochemical properties of the composite material. Particularly, the anode (CNSs-Si-TS) demonstrates a high initial specific capacity of 2069.3 mAh g(-1) and a reversible capacity of 1441.8 mAh g(-1) after 100 cycles at 0.2 A g(-1). Even at 1 A g(-1), its specific capacity maintains 708.07 mAh g(-1) after 300 cycles. The design of a double-layer coating structure provides a promising approach for the preparation of carbon-silicon anode materials.