A comprehensive review of metal oxides (RuO2, Co3O4, MnO2 and NiO) for supercapacitor applications and global market trends

Development of reliable and sustainable energy storage options is becoming increasingly important as we continue to consume more non-renewable fossil fuels. Supercapacitors are a promising solution to this issue due to their high-power density, fast charge/discharge process, and excellent cycle stability. However, while they have many advantages, their energy density is still lower than traditional batteries, and their performance depends on the electrode materials used. Recent advancements in metal oxide-based electrodes have attracted significant attention due to their high specific capacitance and good cycling stability. This review provides an overview of these advancements, specifically focusing on RuO2, MnO2, Co3O4, NiO, and their nanocomposites. These oxide materials are selected as they have excellent reversibility and superior performance in terms of high specific capacitance among the metal oxide community. The review begins by discussing the working principles, types, and factors affecting the performance of these metal oxide-based electrodes. It then highlights the advantages and limitations of metal oxide-based electrodes, compares their performance with other electrode materials, and discusses current challenges and prospects for the development of four metal oxide-based supercapacitors. Lastly, the review explores the effectiveness of metal oxide-based, solid-state, and flexible supercapacitors and discusses the global market for supercapacitors.