Fg -1 at 1 A g -1 in 6 M KOH solution by three-electrode system justifying that the electrochemical oxidation of copper ions to metallic copper is more pronounced at higher temperature. Therefore, both the oxidation of copper ions to cu metal and the interaction of boron and oxygen functionalities with ions in the electrolyte enhance the pseudocapacitance behaviour of the composite that would be attributed to the substantial increase in the performance towards energy storage. The fabricated asymmetric solid-state supercapacitor (ASSC) device in which RGO as the positive electrode and CuBG as the negative electrode delivered an energy density of 132.5 W h kg -1 at a power density of 1000 W kg -1 with H2SO4/PVA as the solid electrolyte at a operating voltage 2.0 V and a current density of 1 A g -1 , respectively. From Fig. and, it was clearly seen that both capacitance and energy density rise with operating voltage and hence the optimized cell voltage is found to about 2 V.