First high-nuclearity mixed-valence polyoxometalate with hierarchical interconnected Zn2+ migration channels as an advanced cathode material in aqueous zinc-ion battery

To date, the research on Zn2+ storage properties of nanosized high-nuclearity polyoxometalate clusters (HNPCs) in aqueous zinc-ion batteries is still unexplored. Herein, we for the first time utilized the nanosized mixed-valence K10[VIV16VV18O82] (KVO) cluster as a Zn2+ storage material to exploit novel Zn/HNPC battery with eminent charge–discharge properties because the 3-D orderly packing of nanosized KVO clusters in the microstructure can engineer and construct multidimensional interconnected Zn2+ migration channels, which can endow the KVO host with high electron and Zn2+ conductivities and high-efficiency Zn2+ migration behavior. As expected, the as-fabricated Zn/K10[VIV6VV18O82] battery exhibits a high reversible capacity of 401 mAh g−1, good cyclic stability with capacity retention of 93% over 4000 cycles at 3 A g−1, and favorable energy (285 Wh kg−1) and power density (4.5 kW kg−1). A quantitative Zn2+ storage mechanism has been proposed based on in-depth insight on Zn2+ intercalation/deintercalation behavior and redox reaction process during cycling. This work not only provides a new zinc-ion battery research platform of HNPCs and opens up a new understanding of the Zn2+ storage mechanism in the POM host, but also demonstrates a tremendous and promising application potential of HNPCs in aqueous batteries.