Electrolyte-dependent performance of SnSe nanosheets electrode for supercapacitors

Transition metal chalcogenides (TMC) are widely suggested as electrode materials for electrochemical energy storage devices due to their layered structure. However, the difficult synthesis limits the commercial utilization of these materials. Herein, we report a simple and effective synthesis method to obtain thin films of SnSe electrodes using the solution heating synthesis route. Having an average thickness of 45 nm, the structural and topographical confirmation of the SnSe nanosheets was revealed by XRD, XPS, SEM, and TEM characterizations. The produced SnSe served as electrodes in aqueous three-electrode supercapacitor cells. When tested with KOH electrolyte, it demonstrated a high specific capacitance of 794 F/g and an areal capacitance of 155 mF/cm² at a scan rate of 5 mV/s. The LiClO₄ electrolyte had a specific capacitance of 645 F/g and an areal capacitance of 103 mF/cm² at a scan rate of 2 mV/s. Furthermore, the SnSe nanosheet electrode maintains 97 % of the maximum capacitance in the LiClO₄ electrolyte for 4500 cycles, even at a high scan rate of 100 mV/s. The symmetric solid-state SnSe supercapacitor device fabrication has been carried out by using PVA-KOH and PVA-LiClO₄ gel electrolytes. The highest estimated energy density from a fabricated symmetric solid-state (SSC) device is 8.88 Wh/kg at a power density of 2.7 kW/kg. Even at 3.0 kW/kg higher power density, the SSC device retained a reasonably good energy density of 4.3 Wh/kg. Finally, to check the durability of the fabricated SSC device has been carried out for long 5000 CV cycles and the specific capacitance retention was around 96 %. The easy synthesis technique for SnSe nanosheets and binder-free electrode fabrication has a promising application in the production of high-performance energy storage devices. The findings of this study hold significant implications for the advancement of supercapacitor technology, offering insights into the potential of SnSe as a high-performance electrode material and shedding light on the critical role of electrolyte selection in achieving superior supercapacitor performance.