Hot-Pressed SnS/rGO Electrodes for High-Power Asymmetric Supercapacitors

Herein, we present the rational engineering of SnS/reduced graphene oxide (rGO) composites to enhance pseudocapacitance through carrier concentration optimization. The orthorhombic pnma-based SnS showed transitions from p- to n-type transport with the addition of rGO. This leads to changes in the bandgap, Fermi levels, conductivity, and diffusion coefficient to achieve the desired properties. The SnS/rGO 5% composite illustrates a specific capacitance of 200 F/g at 1 A/g, three times higher than that of pure SnS owing to its extrinsic pseudocapacitive nature and diffusion-controlled kinetics. The half-cell demonstrates exceptional capacitance retention of 93% over 1200 cycles, attributed to the conducting framework provided by rGO. In a full-cell configuration, using SnS/rGO 5% as the anode and activated carbon as the cathode, an operational voltage of 1.2 V is obtained. This configuration delivers a specific capacitance of 100 F/g at 1 A/g and maintains a capacity retention of 88% at 40 A/g for 5000 cycles. The energy density is 20.081 Wh/kg, and the power density is 22,454 W/kg for the asymmetric SnS/rGO||activated carbon (AC) device. Furthermore, two identical full cells can power a red LED for 128 s, an orange LED for 83 s, and a green LED for 61 s, demonstrating their practical potential in energy storage applications.