Layered Potassium Vanadate K0.5V2O5 as a Robust Cathode Material for Aqueous Zinc-Ion Batteries.

Layered vanadates are promising cathode materials for aqueous zinc-ion batteries (AZIBs). Herein, a layered potassium vanadate K0.5V2O5 is reported as a promising cathode material for AZIBs. It provides a high reversible capacity of 471.1 mAh g-1 with unprecedent cycle life at a harsh low rate of 0.21 C (90.2% capacity retention after 400 cycles, running time 150 days), remarkable rate capability and decent long-term cycling stability (no capacity decay after 1700 cycles). According to a series of tests, it is revealed that the energy storage mechanism of K0.5V2O5 involves initial extraction of K+ followed by subsequent (de)intercalation of Zn2+/H+, in which the concomitant structure change and chemical state transition of vanadium possess high reversibility. Moreover, K0.5V2O5 exhibits rapid Zn2+/H+ ion diffusion, favoring its rate capability. Additionally, K0.5V2O5 also demonstrates excellent low-temperature adaptability, which can operate stably at -30 °C. The excellent electrochemical performance, facile preparation, and low cost of K0.5V2O5 promise it as an attractive cathode candidate for practical AZIBs.