Three-Dimensional Polypyrrole-Decorated CuCo2S4 Nanowires Anchored on Nickel Foam: A Promising Electrode for High-Performance Supercapacitors

The exploitation of high-performance supercapacitors is crucial to promote energy storage technologies. Benefiting from the three-dimensional conductive micronanostructures and high specific capacity of the PPy@CuCo₂S₄@NF (polypyrrole/copper cobalt sulfide/nickel foam) composite electrode, this electrode exhibits a high specific capacity of 1403.21 C g^-1 at 1 A g^-1 and a capacitance retention of 85.79% after 10,000 cycles at 10 A g^-1. The assembled PPy@CuCo₂S₄@NF//AC aqueous hybrid supercapacitor (AHSC) reveals a wide operating potential window of 1.5 V and achieves a high specific capacity of 322.52 C g^-1 at 1 A g^-1 and a capacitance retention of 86.84% after 15,000 cycles at 10 A g^-1. The AHSC also exhibits a high power density of 733.69 W kg^-1 at an energy density of 67.19 W h kg^-1, surpassing those of previously reported spinel-based supercapacitors. Ex situ X-ray diffraction and X-ray photoelectron spectroscopy results show that the CuCo₂S₄ spinel structure changes to CuS₂ and CoS₂ cube structures, and the oxidation states of Cu and Co increase during charging and discharging processes. Density functional theory calculations suggest a superior conductivity for CuCo₂S₄ compared to that for CuCo₂O₄, demonstrating that CuCo₂S₄ has superior electrochemical performance. These findings attest to the considerable potential of the spinel materials for advanced energy storage applications.