Phase-Stabilized Crystal Etching to Unlock An Oxygen-Vacancy-Rich Potassium Vanadate For Ultra-Fast Zn Storage

Despite holding the advantages of high theoretical capacity and low cost, the practical application of layered-structured potassium vanadates in zinc ion batteries (ZIBs) has been staggered by the sluggish ion diffusion, low intrinsic electronic conductivity, and unstable crystal structure. Herein, for the first time, a phase stabilized crystal etching strategy is proposed to innovate an oxygen-vacancy-rich K0.486V2O5 nanorod composite (Ov-KVO@rGO) as a high-performance ZIB cathode. The in situ ascorbic acid assisted crystal etching process introduces abundant oxygen-vacancies into the K0.486V2O5 lattices, not only elaborately expanding the lattice spacing for faster ion diffusion and more active sites due to the weakened interlayer electrostatic interaction, but also enhancing the electronic conductivity by accumulating electrons around the vacancies, which is also evidenced by density functional theory calculations. Meanwhile, the encapsulating rGO layer ably stabilizes the K0.486V2O5 crystal phase otherwise is hard to endure subject to such a harsh chemical etching. As a result, the optimized Ov-KVO@rGO electrode delivers record-high rate capabilities with 462 and 272.39 mAh g-1 at 0.2 and 10 A g-1, respectively, outperforming all previously reported potassium vanadate cathodes and most other vanadium-based materials. This work highlights a significant advancement of layer-structured vanadium based-materials towards practical application in ZIBs. Sluggish kinetics, low conductivity, and unstable structure are the major obstacles that restrict the layered-structured potassium vanadates applied for zinc ion storage. A phase stabilized crystal etching strategy is reported to constructing Ov-KVO@rGO composite cathode that deliver remarkable rate capability (462 and 272.39 mAh g-1 at 0.2 and 10 A g-1), outperforming all potassium vanadate and most vanadium-based materials.image