Defect-engineered vanadium trioxide nanofiber bundle@graphene hybrids for high-performance all-vanadate Na-ion and K-ion full batteries
Sodium- and potassium-ion batteries (SIBs and PIBs) are important for next-generation energy storage. Nevertheless, successful assembly of full-cell SIBs and PIBs is still challenging, notably in the aspect of exploring anode materials with high redox reversibility and stability. It is because ordinary anode materials usually demonstrate slow intercalation/extraction kinetics for the large-radius Na/K-ions. An effective way for addressing this issue is to introduce a high defect density over the entire bulk volume of materials, but it is still a challenge. Here, we report a facile approach to prepare graphene-wrapped vanadium trioxide nanofiber bundles with defects over the entire bulk volume (V2O3−x@rGO). The intercalation pseudocapacitance-dominant V2+/V3+ redox enables the V2O3−x@rGO anodes to demonstrate high-rate Na/K storage and desirable cycling stability. By, respectively, employing graphene-blended V4+/V5+-redox-based sodium vanadate (NaVO@rGO) and potassium vanadate (KVO@rGO) cathodes, new prototypes of all-vanadate full SIBs and PIBs with high capacity and long-term stability over 250 cycles are demonstrated. In particular, the full PIB shows high energy and power densities (157.7 and 96.4 W h kg−1 at 46 and 460 W kg−1, respectively), the best among all reported PIBs.