Optimizing synergistic effects: creating oxygen vacancies in NiCoWO4via a solid-state grinding method for improved energy storage performance†

To address the escalating demand for electrical energy, developing high-performance electrochemical energy storage materials is crucial. Metal oxides represent promising materials for high-energy-density supercapacitors. Among these materials, transition metal-based tungstates exhibit significantly enhanced electrical conductivity compared to pure oxides. However, their low inherent conductivity, restricted electrochemically active sites, significant volume expansion, lower capacity, and deprived cycling stability undermine their electrochemical properties. Herein, we synthesised an oxygen vacancy-enriched NiCoWO₄ electrode by a simple solid-state, solvent-free grinding process using NaBH₄. The Ov-NiCoWO₄ electrode displays an impressive capacitance of 703.66 F g⁻¹ at 1 A g⁻¹ and exceptional cycling stability with 87% retention over 2000 cycles at 7 A g⁻¹. This excellent performance is attributed to the oxygen vacancy in the Ov-NiCoWO₄ material, which increases the electron carrier density, accelerates electron transportation, enhances the active surface area, and boosts the redox reactivity of the material. In the as-prepared real-life supercapacitor configuration of Ov-NiCoWO₄//AC, a determined capacitance of 129.10 F g⁻¹ at 1 A g⁻¹ is achieved. Additionally, it exhibits an energy density of 37.699 W h kg⁻¹ with a power density of 724.98 W kg⁻¹, signifying exceptional performance. Furthermore, it maintains an impressive cycle life, retaining approximately 88.5% over 1000 cycles.