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Nickel cobalt selenide presents a typical Faraday charge storage mechanism, but its electrochemical performance is limited due to its poor reaction kinetics. As a common defect type, vacancy defects can eliminate the limitations of intrinsic chemical and structural characteristics, thereby improving the reaction kinetics of the electrode. Herein, we report a Va-NiCo2Sex nanomaterial with adjustable Se vacancy concentrations achieved by NaBH4 induction, realizing an enhancement of the performance of the supercapacitor. This adjustment of vacancy concentrations can not only essentially regulate the adsorption site and ion valence state and enhance the adsorption capacity and redox activity of ions, but also reveal the significant improvement of vacancy modification on the surface reaction kinetics of electrode materials through density functional theory (DFT) calculation. The electrochemical results show that the V2-NiCo2Sex electrode material with optimal vacancy concentrations has the highest specific capacity of 310.8 mA h g−1 at 1 A g−1. The assembled hybrid supercapacitor V2-NiCo2Sex//AC-HSC can provide a high energy density of 76.5 W h kg−1 at a power density of 800.1 W kg−1. This work provides an effective strategy for exploring the structure–function relationship between vacancy concentrations and electrochemical performance. [ABSTRACT FROM AUTHOR]

Transition metal selenide is a typical pseudocapacitive material used in supercapacitor electrodes, but its practical application is restricted due to its insufficient utilization rate of active sites and slow kinetics of redox reaction. Defect engineering can effectively adjust the electronic structure, provide additional intercalation sites, and realize the regulation of energy storage mechanism within the lattice. At present, heteroatom doping is an effective strategy that can provide abundant vacancy defects by introducing heterogeneous atoms, thereby achieving significantly improved electrochemical performance. Based on this, NiCo2Se4 electrode materials with Se vacancies were prepared by P doping for supercapacitors. The double-effect synergy of P doping and vacancy engineering can effectively change the electronic structure and improve the adsorption capacity of ions, which are more prone to redox reactions. The assembled hybrid supercapacitor (NiCo2Sex-P1//AC) has 90.2% capacity retention and 100% coulombic efficiency after 10 000 consecutive charge–discharge cycles, and it exhibits a high energy density of 94.6 W h kg−1 at a power density of 799.9 W kg−1. This provides an effective strategy for constructing high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Transition metal selenide is a typical pseudocapacitive material used in supercapacitor electrodes, but its practical application is restricted due to its insufficient utilization rate of active sites and slow kinetics of redox reaction. Defect engineering can effectively adjust the electronic structure, provide additional intercalation sites, and realize the regulation of energy storage mechanism within the lattice. At present, heteroatom doping is an effective strategy that can provide abundant vacancy defects by introducing heterogeneous atoms, thereby achieving significantly improved electrochemical performance. Based on this, NiCo2Se4 electrode materials with Se vacancies were prepared by P doping for supercapacitors. The double-effect synergy of P doping and vacancy engineering can effectively change the electronic structure and improve the adsorption capacity of ions, which are more prone to redox reactions. The assembled hybrid supercapacitor (NiCo2Sex-P1//AC) has 90.2% capacity retention and 100% coulombic efficiency after 10 000 consecutive charge–discharge cycles, and it exhibits a high energy density of 94.6 W h kg−1 at a power density of 799.9 W kg−1. This provides an effective strategy for constructing high-performance supercapacitors. [ABSTRACT FROM AUTHOR]