Silicon-carbon anode with high interfacial stability by a facile thermal reaction involving alkaline nitrogenous carbon source for lithium ion batteries

Silicon‑carbon composites are considered one of the most promising anodes for high-energy lithium-ion batteries. In this work, NC@Si nanospheres were prepared as silicon‑carbon anode materials for lithium-ion batteries by using an alkaline nitrogenous carbon source (polydopamine, PDA) to induce the anchoring of ultra-fine and high-purity SiO2 quantum dots onto a carbon matrix, followed by a magnesium thermal reduction treatment. The small volume expansion of silicon quantum dots (<10 nm) in NC@Si nanospheres and the thin Si3N4 outerwear formed on Si quantum dots due to the diffusion of N atoms and the local high temperature of magnesium heat synergistically ensure the structural integrity of NC@Si nanospheres and inhibit the excessive formation of SEI. The multi-point solid electrical contact between the silicon quantum dots and the nitrogen-doped carbon matrix provides sufficient conductive channels for fast Li+ diffusion and charge transfer. The as-prepared NC@Si anode exhibits a specific capacity of 497.2 mAh g−1 at 0.1 A g−1 with a capacity retention of 75.4% after 100 cycles, demonstrating a stable cycling performance. In the NC@Si||LFP full cell, the anode maintains a reversible capacity of 260.8 mAh g−1 after 80 cycles. The investigation of NC@Si composite anode proves that the silicon‑carbon anode by a facile thermal reaction involving alkaline nitrogenous carbon source can effectively improve the defects of silicon, offering the possibility of commercial application of silicon-based anode.