An in-situ structural self-optimization strategy toward Ca1-xV3O7 cathode for aqueous zinc-ion batteries with ultra-high capacity and lifespan

Exploring excellent electrode material with high structural stability and rapid ions dynamics is the key challenge for achieving high capacity and long-term cycling stability aqueous zinc-ion batteries (AZIBs). Herein, we design a layered Ca1-xV3O7 cathode via an electrochemical in-situ structural self-optimization method. Removing a large amount of calcium ions from the parent phase structure not only provides effective space for the storage of zinc ions, but also significantly improves the ions transfer dynamics. At the same time, the residual Ca ions acts as 'pillar' to stabilize the layered structure and effectively avoid the structural collapse phenomenon of the layered vanadium oxide cathode during cycling. As a result, the self-optimized Ca1-xV3O7 (x = 0.84) cathode exhibits a high reversible capacity of 512 mA h g-1 at 0.1 A/g and impressing long lifespan in different current density condition. Furtherly, with the aid of the in-situ characterization technology, the reversible zinc ions storage mechanism of the Ca1-xV3O7 is revealed in detail. More importantly, by adjusting the x value of Ca1-xV3O7, we provide a new microcosmic perspective on the Ca2+- Zn2+ buffering mechanism in the host of Ca1-xV3O7 by DFT calculations and experimental evidence, which provides a guideline for rational design of the high-performance layered vanadium oxide cathodes for ZIBs.