Surface functional group-tailored B and N co-doped carbon quantum dot anode for lithium-ion batteries

Recently, carbon quantum dots (CQDs) have emerged as new surface modification agents for the anode materials of lithium-ion batteries (LIBs) owing to their various advantages, including high surface area, low toxicity, low cost, and chemical stability. However, CQDs intrinsically possess large amounts of nonessential oxygen-containing groups (C-O and C-OH) at the surface, which can inhibit Li⁺ accessibility and lower electrical conductivity. Owing to these limitations, CQDs have been widely studied as composite agents and not as independent active materials. Therefore, to enhance the electrical conductivity and increase the Li⁺ diffusivity of CQDs, we suggest surface functional group-tailored boron and nitrogen co-doped carbon quantum dots (BN-CQDs) for self-reliant LIB anode applications. The 0.5BN-CQD electrodes showed superior electrochemical performance, including outstanding ultrafast energy storage capability (130.4 mAh g⁻¹ at 3000 mA g⁻¹ with capacity retention of 88% up to 1000 cycles). This is contributed by the enhanced electrical conductivity of the boron and nitrogen co-doped structure and high Li⁺ acceptability, which facilitated the formation of C═O surface functional groups due to the boron dopant. In this regard, we believe that the fabrication of self-reliant 0.5BN-CQD electrodes could be a promising research strategy for carbon-based anode materials.