Electrochemically Induced Structural and Morphological Evolutions in Nickel Vanadium Oxide Hydrate Nanobelts Enabling...

Suitable intercalation cathodes and fundamental insights into the Zn-ion storage mechanism are the crucial factors for the booming development of aqueous zinc-ion batteries. Herein, a novel nickel vanadium oxide hydrate (Ni_0.25V₂O₅·0.88H₂O) is synthesized and investigated as a high-performance electrode material, which delivers a reversible capacity of 418 mA h g^-1 with 155 mA h g^-1 retained at 20 A g^-1 and a high capacity of 293 mA h g^-1 in long-term cycling at 10 A g^-1 with 77% retention after 10,000 cycles. More importantly, multistep phase transition and chemical-state change during intercalation/deintercalation of hydrated Zn²⁺ are illustrated in detail via in situ/ex situ analytical techniques to unveil the Zn²⁺ storage mechanism of the hydrated and layered vanadium oxide bronze. Furthermore, morphological development from nanobelts to hierarchical structures during rapid ion insertion and extraction is demonstrated and a self-hierarchical process is correspondingly proposed. The unique evolutions of structure and morphology, together with consequent fast Zn²⁺ transport kinetics, are of significance to the outstanding zinc storage capacity, which would enlighten the mechanism exploration of the aqueous rechargeable batteries and push development of vanadium-based cathode materials.