Boron quantum dot powered anthracite-derived carbon anode achieving enhanced reaction kinetics and superior sodium storage capability†

Abstract

Low-cost and mass-produced anthracite is used herein as a carbon precursor to prepare a carbon anode for sodium-ion batteries (SIBs) through NaOH activation and a one-step carbonization process. To enhance the reaction kinetics and boost the sodium storage capability of anthracite-derived carbon (AC), boron quantum dots (BQDs) were fabricated and incorporated into the AC framework through simple freeze-drying of the mixtures with BQDs and AC and an annealing process. The electron-deficient properties of quantum-sized boron endow the AC framework with outstanding electrochemical performance. The ordered and disordered mixed structure of the AC framework provides more active sites for ion insertion and extraction, thus increasing capacity and improving the diffusion and transfer of both ions and charges. The boron solid-solution phases, such as BC₃, BC₂O and BCO₂, formed within the AC framework make it easier to store and release sodium ions, thereby achieving efficient sodium-ion adsorption and desorption during the charge–discharge process. Thus, the as-prepared BQDs/AC-1300 anode exhibits a high initial discharge capacity of 568.2 mA h g⁻¹ at 25 mA g⁻¹, a large reversible capacity of 287.5 mA h g⁻¹ at 50 mA g⁻¹, and superior long-term cycling stability of 89.8 mA h g⁻¹ at 1000 mA g⁻¹ over 1000 cycles. Galvanostatic intermittent titration analysis indicates that boron electron deficiencies create more ion adsorption sites and boost the pseudocapacitive charge storage capability, exhibiting remarkable charge transfer kinetics between sodium and active materials. The protocol for powering an anthracite-based anode by embedding BQDs should inspire far-ranging investigations into boron-based advanced battery systems.