Tuning vacancy and size of metallic VCx quantum dots for capacitive potassium-ion batteries

Abstract

Potassium-ion batteries (KIBs) are an emerging, promising and low-cost energy storage technology, but the study on KIBs is in the early stage. In this work, we design a unique 3D foam-like composite by encapsulating carbon vacancies assisted VCx quantum dots within ultralarge highly N-doped macroporous carbon microsheets. The composite is synthesized by an ultrafast solution combustion synthesis method (completed within two minutes) and a subsequent carbothermal reduction process, easily amenable to large-scale processing. By tuning the vacancy and size of VCx quantum dots, improved electronic conductivity and highly reversible K+ adsorption are achieved. As an effective support, the foam-like high-level N-doped macroporous carbon microsheets offer significant advantages by enhancing the electronic conductivity and K+ mobility. The optimized sample presents a promising anode for capacitive potassium-ion batteries, which delivers a high capacity and a high cycling stability (345 mAh g−1 at 0.05 A g−1 in 100 cycles tests, and 130 mAh g−1 at 1 A g−1 even after 1500 cycles), among the best anode materials reported for KIBs. Equally importantly, the effective strategy can be easily mass produced and also potentially used for producing other carbides/carbon composites in energy storage.