Local pH regulation at zinc vanadate cathode by a hierarchical structure for long-life aqueous zinc batteries.

[Display omitted] • Prepare a novel hierarchical structured cathode for aqueous zinc batteries. • The hierarchical cathode shows ultra-long cycle life. • Nanorod arrays on the hierarchical cathode regulate the local electric field. • Tip effect accumulates protons near the surface to inhibit the side reaction. Vanadium-based oxides are promising cathode candidates for aqueous zinc batteries, but their cycling stability is unsatisfactory. Herein, a unique hierarchical structured zinc vanadate material, with amorphous nanorod arrays standing on crystalline lamellar plates, is produced by the in-situ electrochemical conditioning from a H 0.39 V 2 O 5 precursor. The hierarchical cathode achieves a high capacity of 536 mAh/g at 0.1 A/g and 344 mAh/g at 5 A/g. Importantly, a long life of 10,000 cycles with 88% capacity retention is realized at 5 A/g. Finite-element analysis shows that the tip effect of the nanorod arrays accumulates protons near the surface of the hierarchical cathode. The resulting locally low-pH environment prevents vanadium dissolution and formation of inactive Zn 3 V 2 O 7 (OH) 2 ·nH 2 O during cycling, which ensures the high cycling stability. This work presents insights into local pH regulation to optimize the cycling stability of cathode materials in aqueous zinc batteries. [ABSTRACT FROM AUTHOR]