Investigation of Electrochemical Charge Storage Efficiency of NiCo2Se4/RGO Composites Derived at Varied Duration and Its Asymmetric Supercapacitor Device

Morphology and crystalline structure of electrode materials control the capacitive properties of a supercapacitor device. Among the commonly studied electrode materials, Ni–Co-based bimetallic selenides are recognized as a promising supercapacitor electrode. Herein, NiCo2Se4/reduced graphene oxide (NCSRG) composites are synthesized by a two-step facile hydrothermal reaction for high-performance supercapacitor applications. The synthesis process is explored using a time-dependent experiment. The duration of the hydrothermal reaction controls the morphology of the electrode materials, which further affect the electrochemical performance. Specific capacitance of nickel–cobalt carbonate hydroxides (NCRGs) improves remarkably after Se interrogation. It is found that 12 h reaction products exhibit the highest capacitance properties among the intermediate NCRGs and final products (NCSRGs). An asymmetric supercapacitor (ASC) cell is fabricated using positive (NCSRG-12) and negative (TRGO) electrodes (TRGO//NCSRG-12). It is found that the specific capacitance of the ASC device is ∼139 F g–1 at a 2 A g–1 current density with a working potential of ∼1.4 V. The device delivers an energy density of ∼37.83 W h kg–1 and a power density of 1433.55 W kg–1. The loss of specific capacitance is ∼12.73% after 5000 galvanostatic charge–discharge (GCD) cycles.