Vacancy and surface modulation engineering of CuxCo3-xO4 nanowires as an advanced cathode for zinc-ion hybrid supercapacitors

Zn-ion hybrid supercapacitors (ZHSCs) with high power and energy density have great potential in energy storage applications such as hybrid vehicles and renewable energy storage. However, the large radius of hydrated Zn2+-ions hampers their efficient storage in micropores with limited pore sizes, resulting in limited weight ratio capacitance and poor rate capability of ZHSCs. In this study, we developed the novel N-doped and oxygen vacancy-rich CCO nanowires (N-Ov-CCO@CC) architecture with the help of Chemical Vapor Deposition (CVD). Due to the guiding synergy of N-doping, defects, and surface engineering, N-Ov-CCO@CC exhibits significantly enhanced electrochemical performance. The N-Ov-CCO@CC single electrode exhibits excellent charge storage properties, including a high capacitance of 1480.7 F/g at 1 A/g, excellent rate-capability (88.4 % at 20 A/g), and excellent cycle stability of up to 90.1 % for 5000 cycles. The charge storage mechanism was analyzed by ex-situ XRD and XPS, and it reveals that the pseudocapacitive charge storage characteristics are dominant. Operating in the potential range of 1.2-2.0 V, the N-Ov-CCO@CC//Zn-ZHSC provides a high capacitance of 308.2 F/g at 1 A/ g, excellent rate capability (86.9 % at 10 A/g), long lifetime (97 % after 10,000 cycles), and high specific energy/ power (134.32 Wh/kg at 9507.6 W/kg). Density function theory (DFT) validations show that the N-Ov-CCO system possesses higher conductivities than Ov-CCO and pristine CCO. This work provides an effective strategy for constructing multifunctional electrochemical energy materials for ZHSCs.