Recent advances in hydrothermally and solvothermally grown Co3O4 nanostructures for electrochemical energy storage (EES) applications: a brief review

The increasingly intimate connection between energy generation, energy storage difficulties, and the growing human energy demands necessitates the invention and development of energy storage electrodes/devices. In recent years, spinal structured Co3O4, coupled with several fascinating features such as high redox activity, different oxidation states, and high theoretical capacitance, has found widespread use as a promising material for electrochemical energy storage (EES) applications. This review outlines the progress of pristine Co3O4 electrodes under high-pressure conditions (hydrothermal and solvothermal) over the last three decades for EES applications. Nowadays, developing hybrid nanostructures, doping, and tailoring nanostructure morphology are the most widely used strategies to fabricate highly efficient EES devices. However, so far pristine Co3O4 as an active electrode material with different dimensionalities for EES applications has been prepared using several strategies (such as using surfactants, templates, and various agents or changing the reaction conditions), via hydrothermal/solvothermal techniques, and specific strategies have been substantiated to be highly effective in enhancing its overall performance. Hence, it is essential to analyze it systematically to be beneficial for future studies. Furthermore, this review provides an overview of symmetric and asymmetric energy storage devices based on synthesized Co3O4 electrodes. This report provides statistical data on EES performance metrics of pristine Co3O4 electrodes and Co3O4-based devices, as stated in the published literature. The present study provides the key perspectives on next-generation Co3O4-based EES research.