A mass-producible polyoxovanadate cathode for ultrafast-kinetics zinc-ion batteries

Abstract

Aqueous zinc-ion batteries (ZIBs) have emerged as a high-safety, cost-effective, and environment-benign energy storage solution for grid-scale applications, however, the lack of high-performance cathode materials that support rapid zinc ion migration and allow scalable synthesis has hindered their commercialization. In this work, we propose a low-cost and mass-producible polyoxovanadate KZnV₅O₁₄·2.5H₂O (KZVO) cathode, demonstrating a high specific capacity of 275 mA h g⁻¹ and an energy density of 201 W h kg⁻¹. Notably, the special crystal structure is rich in large decavanadate complexes connected by weak hydron bonds and coordinated potassium/zinc ions, giving rise to criss-crossed zinc ion transportation channels and thus a relatively low hopping energy barrier (0.58 eV), comparable to that of lithium ion in LiFePO₄. The intrinsic ultrafast ion-diffusion kinetics enables the achievement of an ultrahigh power density (6.8 kW kg⁻¹ at 127 W h kg⁻¹) and the ultrafast charging capability (70% state of charge in one minute) at an extremely high rate of 40 C (10 A g⁻¹). Apart from the high abundance and full availability of both zinc and vanadium, the high capacity, decent cycling stability, and excellent rate capability render the study of KZVO a fresh perspective on advancing the development of cathode materials for ZIBs.