Co/Ni Oxide electrodes for High Performance Supercapacitors

Abstract

The growing demand for efficient and sustainable energy storage systems has stimulated extensive research into advanced supercapacitor electrode materials. Among the various transition metal oxides, those based on cobalt and nickel have emerged as promising candidates due to their rich redox behaviour, multiple oxidation states, and high theoretical capacitance. Notably, mixed Co/Ni oxides have demonstrated superior electrochemical performance compared to individual metal oxides, attributable to the synergistic interaction between cobalt and nickel ions. Recent advancements in nanostructure engineering have significantly enhanced the electrochemical properties of these materials by improving surface area, electrical conductivity, and ion/electron transport pathways. This review offers a comprehensive overview of Co/Ni oxide-based materials for high-performance supercapacitor applications. The fundamental mechanisms of charge storage and key electrochemical parameters are succinctly examined. Various synthesis methods, including hydrothermal, sol–gel, co-precipitation, and electrodeposition techniques, are analysed with a focus on their impact on morphology and electrochemical behaviour. Various nanostructured architectures, such as nanosheets, nanowires, nanoflowers, and hierarchical structures, are analysed with respect to their specific capacitance, rate capability, and cycling stability. Furthermore, the primary challenges related to conductivity, structural degradation, and large-scale fabrication are examined, alongside potential strategies for enhancing performance. Ultimately, future directions for the advancement of durable and efficient Co/Ni oxide supercapacitors are discussed.