Unexpected role of the interlayer "dead Zn${}^{2+}$" in strengthening the nanostructures of VS${}_2$ cathodes for high-performance aqueous Zn-ion storage

Layered VS${}_2$ holds great potential as a cathode material for aqueous Zn-ion batteries owing to its large interlayer spacing, high electrical conductivity, and the rich redox chemistry of vanadium. Nevertheless, structural instability during charge/discharge severely hinders the further development of VS${}_2$ cathodes. Herein, distinctive hierarchitectures of 1T-VS${}_2$ nanospheres assembled by nanosheets, which feature abundant active sites, superior electron/ion transport property, and robust structure, are developed. More intriguingly, Zn${}^{2+}$ "pillars" residing in VS${}_2$ interlayers, achieved by controlling the charge cut-off voltage are first proven to reinforce the layered structure of VS${}_2$ upon repeated Zn${}^{2+}$ insertion/extraction, redefining the commonly perceived "dead Zn${}^{2+}$". Hence, exceptional rate performance (212.9 and 102.1 mA h g${}^{-1}$ at 0.1 and 5 A g${}^{-1}$, respectively) and ultralong cycling life (86.7% capacity retention over 2000 cycles at 2 A g${}^{-1}$) are obtained. The rapid and highly reversible Zn-ion (de) intercalation behavior within the VS${}_2$ nanospheres is verified by first-principles computations and multiple ex-situ characterizations. Finally, the flexible quasi-solid-state rechargeable Zn battery employing the tailored VS${}_2$ cathode demonstrates great application prospects in wearable devices. This work provides new perspectives for prolonging the lifespan of layered Zn-storage materials by simply modulating the charge/discharge processes. (© 2022 Wiley-VCH GmbH)