Incorporating quantum-sized boron dots into 3D cross-linked rGO skeleton to enable the activity of boron anode for favorable lithium storage

Abstract Boron has drawn intensive attention as a competitive anode candidate for next-generation high-energy rechargeable batteries. However, the large-scale application of boron anodes for practical batteries is still hindered by their electrochemical inertness caused mainly by the strong covalent bond in the aggregate boron backbone. Herein, quantum-sized boron dots (BQDs) were synthesized by the low-temperature liquid-phase exfoliation of boron nanosheets and incorporated into the conductive graphene matrix, consequently forming a 3D cross-linked BQDs/reduced graphene oxide (B@rGO) skeleton as high-performance anodes for lithium-ion batteries. Decreasing the size of boron to the quantum-sized scale vastly enables the electrochemical activity of boron as well as provides more active sites for ion insertion and extraction, thus increasing capacity and improving ion/charge diffusion and transfer. The 3D cross-linked conductive structure activates BQDs to store/release lithium reversibly, and endows the interrelated macroporous/mesopores, where the electrolyte can effortlessly access the conveying pathways and active sites for efficient Li+ adsorption and desorption. The developed anodes thus harvest remarkable electrochemical properties in terms of ultrahigh capacity of 2651 mAh g−1 at a current density of 0.05 A g−1, outstanding long-term cycling stability of 836 mAh g−1 at 0.1 A g−1 over 500 cycles, and excellent rate performance (even after enduring five consecutive current rates changing from 0.1 to 10 A g−1, it still delivers a capacity of 202 mAh g−1 at 10 A g−1). The protocol to boost the electrochemical performance by introducing BQDs could inspire wider explorations on other advanced anode materials.