Synthesis of rod-like ternary Cu(Cd)-In-S and quaternary Cu-Cd-In-S by controlled ion exchange of MIL-68(In) derived indium sulfide for high energy-storage capacitor

Abstract A facial solvothermal method is developed to prepare rod-like MIL-68(In) derived In2S3. By partially ion exchange procedure, as prepared In2S3 (IS) is being used for the fabrication of copper doped indium sulfide (CIS), cadmium doped indium sulfide (CdIS), and finally Cd, Cu co-doped indium sulfide (CdCIS). These composites used as electrode materials for the cathode of supercapacitors (SCs). It is found that the IS, CIS, CdIS, and CdCIS exhibit capacitive performance with a specific capacitance and specific capacity as high as 162, 250.8, 286, and 402.4 F g-1 (22.5, 34.8, 39.7 and 55.8 mAh g-1), respectively at current density of 2 A g-1 in the three-electrode measurement. The CdCIS electrode material experiences a significant growth in its specific capacitance because of the synergistic effect of co-doping of Cd, Cu in the composite, which can decrease the electrical resistivity of the composite and facilitate the movement of electrons among the active components. Also, the asymmetric supercapacitor (ASC) was successfully assembled with CdCIS as cathode and activated carbon (AC) as anode electrodes which shows excellent capacitance for usable energy storage applications. The CdCIS//AC ASC device exhibited a power density of 400 W kg-1 and an energy density of 5.2 Wh kg-1. Even within an ultra-short charging time of 0.35 s, the CdCIS//AC ASC device shows a high-power density of 11.63 kW kg-1 at an energy density of 1 Wh kg-1 and has long-term cycling performance with preservation of 90.2% after 2000 recharge cycles, suggesting their potential for use in high-performance electrochemical capacitors.