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

Abstract

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 {NiMo₆} clusters within a metal-organic framework (MOF), designated as Ni-BTC@{NiMo₆}. 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.

Keywords

Polyoxometalates / Metal-organic framework / {NiMo₆} / Aqueous sodium-ion capacitors / Asymmetric capacitor / Ni-BTC

RIGHTS & PERMISSIONS

2026 SIOC, CAS, Shanghai, & WILEY-VCH GmbH