Ternary-metal-sulfide 2MnS/Cu2S/xZnS/C (x = 0, 0.5, 1, 2, 3) electrodes for high performance supercapacitors

With the development of the consumer society, low cost and high performance supercapacitors are being pursued. To realize the practical supercapacitors, developing the cheap and highly capacitive electrode is the most essential. However, it is a harsh challenge to achieve this target based on single-component electrode. Herein, a series of inexpensive ternary-metal-sulfides, 2MnS/Cu₂S/xZnS/C (x = 0, 0.5, 1, 2, 3) are synthesized by hydrothermal reaction and the subsequent calcination with expired manganese/copper gluconates as the raw materials for the electrode in the pseudocapacitors. Furthermore, the effect of ZnS's content on the electrochemical properties of the ternary composites is also investigated. Specially, the optimal 2MnS/Cu₂S/xZnS/C(x = 1) can output a specific capacitance of 1608 F/g at 1 A/g in the three-electrode system, while the 2MnS/Cu₂S/xZnS/C||AC(x = 1) asymmetric supercapacitor can deliver a specific capacitance of 194 F/g at 1 A/g with the desirable energy density (800 W/kg) and power density (70.9 Wh/kg), higher than those of other samples. Especially, even after 2000 cycles at 5.0 A/g, the 2MnS/Cu₂S/xZnS/C||AC(x = 1) asymmetric supercapacitor also delivers the reversible specific capacitance of 103 F/g with high capacitance retention of 97.0 %, indicating high cycling stability. The outstanding performances of the optimal 2MnS/Cu₂S/xZnS/C(x = 1) may be attributed to the bridge-effect of ZnS component, which makes up for the low conductivity of MnS component and the low capacitance of Cu₂S component, thus achieving the best synergistic effect of ternary metal sulfide 2MnS/Cu₂S/xZnS/C(x = 1) .