Abstract
Mixed transition metal sulfides are promising materials for positive electrodes of asymmetric supercapacitors because they have a large potential for increasing the electrical characteristics of these devices. The paper presents the results of a study of a material based on spinel CuCoNiSxO4−x with both sulfide and oxide sublattices, prepared by a one-step hydrothermal method directly on nickel foam, forming an array of whiskers. Electrochemical studies showed that a positive electrode, CuCoNiS2O2, exhibited a high specific capacitance of 3612 F g−1 at a current density of 1 A g−1. The assembled asymmetric supercapacitor with activated carbon as a negative electrode achieved a specific capacitance of 133.5 F g−1 at 1 A g−1 and a potential window of 1.7 V. Its energy density was 53.6 Wh kg−1 at a power density of 805 W kg−1 and the power density reached 17,000 W kg−1 at an energy density of 18.9 W h kg−1. The assembled device exhibits 52% of capacitance retention after the 20,000 cycles at a current density of 10 A g−1 with 97% coulombic efficiency. These results demonstrate that the CuCoNiSxO4−x system is competitive with other quaternary transition metal sulfides, and this type of spinel is a perspective electrode material for high-performance supercapacitors.