Carbon quantum dot-assisted VO2(D) welding on holey graphene for zinc-ion battery cathode materials

Abstract

Superior-quality zinc-ion batteries utilizing nanopseudocapacitor materials and flexible, three-dimensional, highly conductive porous carbon materials are current research hotspots. But the inadequate dispersion between the system components and the dissolution of the pseudocapacitive materials severely limit the further application of VO2-watery zinc-ion battery components (ZIBs). In this work, we create a novel type of independent VO2(D) covered with carbon quantum dots and assist in its welding on holey graphene (CVH). Composite structures of graphene-supported VO2(D) were designed by a simple solvothermal reaction and ultrasonic self-assembly. The CQD coating acts as a conductive medium, facilitating charge transfer to the surface and also mechanically stabilizing the cathode during volume changes, while the CQD acts as a “bridge” to form an intimate interfacial relationship with the HG. The introduction of HG not only provides more sites of activity and longitudinal transport pathways for electron and ion diffusion, but also makes the overall structure more stable and effective in eliminating the effect of volume change and realizing large pseudocapacitance. The electrochemical results show that CVH has an ultra-strong specific capacity of 443 mA h g−1 at 0.1 A/g, and a capacity retention of 332 mAh g−1 after 1000 cycles at 0.5 A/g. Excellent electrochemical performance for Zn2+ ion storage is found in CVH. This unusual structure may help us understand developing ZIB cathodes better while also offering fresh perspectives on high-performance batteries.