Steering in-situ low-voltage phase transition from spinel to layered cathode for high-performance zinc-ion batteries

ZnV2O4, as a ternary transition metal oxides (TOMs), has garnered significant attention as a high-performance cathode for zinc-ion batteries (ZIBs) primarily due to its high theoretical capacity and abundance. However, its densely-packed lattice structure and strong coulomb interactions with the guest Zn2+ severely restrict the exposure of active sites and impede the diffusion kinetics. Herein, we propose an innovative in-situ low-voltage phase transition strategy and successfully trigger thorough phase transition of spinel-structured ZnV2O4 to layered-structured Zn3(OH)2V2O7⋅2H2O (ZnVOHNSs). In-depth mechanism analysis reveals that a thorough and efficient transition reaction necessitates meticulous control of the external driving force, reaction kinetics, and the reactant. The activated ZnVOHNSs with large lattice spacing and abundant oxygen vacancies provides an unobstructed pathway for accelerated ion diffusion and abundant exposed active sites for ions storage. Moreover, the inherent structure stability of ZnVOHNSs ensures exceptional reaction stability and reversibility during the Zn2+ intercalation/deintercalation process. Benefiting from these merits, the activated ZnVOHNSs cathode exhibits high reversible capacity and extraordinary rate capability (achieving 369 and 233 mAh g−1 at 0.1 and 20 A g−1, respectively), which exceeds most reported cathode materials in ZIBs. This work unveils the critical phase transition mechanism and offers insight into electrode design for advanced batteries.