Unlocking Redox Activity in Confined Polyoxometalates via Atomic Nickel Activation for Aqueous Sodium‐Ion Capacitors

Comprehensive Summary The development of aqueous sodium‐ion energy‐storage systems that combine high energy density, high power density, and long cycle life is crucial for enabling the large‐scale integration of renewable energy. Herein, we report a high‐performance composite electrode material constructed by encapsulating Anderson‐type polyoxometalate {NiMo 6 } clusters within a metal‐organic framework (MOF), designated as Ni‐BTC@{NiMo 6 }. This confinement architecture effectively suppresses cluster dissolution and, by leveraging the electronic synergy between the Ni center and the Mo‐O structure, significantly enhances charge‐transfer kinetics. The material exhibits predominantly surface‐controlled pseudocapacitive behavior, delivering a high specific capacitance of 956.2 F·g –1 at 1.0 A·g –1 . An asymmetric aqueous sodium‐ion hybrid supercapacitor assembled with this material achieves an energy density of 91.3 Wh·kg –1 along with excellent cycling stability (negligible capacitance decay after 5,000 cycles). This work demonstrates the considerable potential of precise integration between molecular clusters and porous frameworks for designing advanced energy‐storage materials.