Boosting lithium storage performance of Si nanoparticles via thin carbon and nitrogen/phosphorus co-doped two-dimensional carbon sheet dual encapsulation

Silicon (Si) is a promising anode candidate for next-generation lithium-ion batteries (LIBs), but it suffers from poor electronic conductivity and dramatic volume variation during cycling, which poses a critical challenge for stable battery operation. To mitigate these issues simultaneously, we propose a “double carbon synergistic encapsulation” strategy, namely thin carbon shell and nitrogen/phosphorus co-doped two-dimensional (2D) carbon sheet dual encapsulate Si nanoparticles (denoted as 2D NPC/C@Si). This double carbon structure can serve as a conductive medium and buffer matrix to accommodate the volume expansion of Si nanoparticles and enable fast electron/ion transport, which promotes the formation of a stable solid electrolyte interphase film during cycling. Through structural advantages, the resulting 2D NPC/C@Si electrode demonstrates a high reversible capacity of 592 mAh·g⁻¹ at 0.2 A·g⁻¹ with 90.5% excellent capacity retention after 100 cycles, outstanding rate capability (148 mAh·g⁻¹ at 8 A·g⁻¹), and superior long-term cycling stability (326 mAh·g⁻¹ at 1 A·g⁻¹ for 500 cycles, 86% capacity retention). Our findings elucidate the development of high-performance Si@C composite anodes for advanced LIBs.