SCHEDULED MAINTENANCE
Gradient valence-distributed vanadium oxygen hydrate hybrid induces high performance aqueous zinc-ion batteries†
*ab
Xing
Li
*ab
Abstract
Gradient valence-distributed vanadium oxygen hydrate hybrid (G-VOH) nanowires are designed by one-step hydrothermal synthesis for aqueous zinc-ion batteries. It is mainly constructed by superficial NH4+-intercalated VOH ((NH4)2V10O25·8H2O, named as NVOH) and inner deeper vanadium reduction VOH (V3O7·H2O, named as VOH). In the unique nanostructure, both NVOH and VOH are active matrices involved in the Zn2+ electrochemical reaction. Moreover, the outer NVOH functions as a Zn2+ transport framework to provide fast Zn2+ transport capability for the inner VOH. Additionally, the gradient vanadium valence distribution in hybrids enhances the vanadium multi-valence redox kinetics, resulting in significant improvement for the Zn2+ storage capacity. Meanwhile, NVOH also functions as a framework support to suppress the inner VOH crystal structure conversion during the charge/discharge process, facilitating its electrochemical stability. Thus, the G-VOH nanowires obtain a high specific capacity of 434 mA h g−1 at 0.1 A g−1, as well as long cycling stability with 86% capacity retention at 2 A g−1 after 1500 cycles. Moreover, the assembled quasi-solid-state G-VOH||Zn batteries achieve a superior specific capacity of 241 mA h g−1 at 1 A g−1 with a capacity retention of 74% after 500 cycles. The strategy of the preparation of gradient valence-distributed vanadium oxygen hydrate provides a new idea for the development of cathode materials for aqueous zinc-ion batteries.
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