Enhanced energy storage performance of Cu₂SnS₃@rGO electrode in pouch-type asymmetric supercapacitors

Abstract

Copper tin sulfides are extensively investigated as an electroactive material for energy storage applications due to their higher theoretical pseudocapacitance. The combination of pseudocapacitance behavior of Cu₂SnS₃ and double layer capacitance behavior of rGO is expected to boost the electrochemical property of the electrode. Here, the rGO supported Cu₂SnS₃ nanocomposite was prepared by using the hydrothermal method. The pure and rGO loaded samples were found to have a tetragonal structure from the XRD analysis and the Raman spectra confirm the formation of rGO supported Cu₂SnS₃ from the D and G bands arising along with Cu₂SnS₃ vibrational modes. Moreover, the flower-shaped Cu₂SnS₃ was covered by rGO nanosheet and is illustrated in the SEM and HRTEM analysis. Also, the Cu₂SnS₃@rGO-2 electrode delivers a higher capacitance value of 630 F/g at 1 A/g, which is much higher than Cu₂SnS₃, Cu₂SnS₃@rGO-1, Cu₂SnS₃@rGO-3 and Cu₂SnS₃@rGO-5 electrodes. The cyclic efficiency of the Cu₂SnS₃@rGO-2 showed 98.38% which is higher than the Cu₂SnS₃ (92.59%), Cu₂SnS₃@rGO-1 (96.61%), Cu₂SnS₃@rGO-3 (98.5%) and Cu₂SnS₃@rGO-5 (97.17%) electrodes over 2000 cycles. Further, the fabrication of asymmetric supercapacitor device, the positive electrode is Cu₂SnS₃@rGO-2 electrode and the activated carbon (AC) as the negative electrode for asymmetric type supercapacitor devices using 1 M KOH electrolyte dipped filter paper is the separator. The Cu₂SnS₃@rGO-2//AC device showed the maximum capacity value of 71.33 mAh/g. Also, the energy and power densities were 47.55 Wh/kg and 1600 W/kg, respectively, at a current density of 1 A/g. In addition, the Cu₂SnS₃@rGO-2//AC device has higher capacitance retention of 73.26% for 10,000 cycles. The addition of rGO is used to improve electrical conductivity and elevate the volume charge of the Cu₂SnS₃ electrode.