Frontiers in transition metal oxide-based composites for high-performance supercapacitors: A comprehensive review

The demand for affordable and eco-friendly energy storage solutions is essential to meeting the challenges of integrating next-generation energy sources. Supercapacitors (SCs) have the potential to be a key electrochemical storage technology for intermittent renewable energy sources due to their long cycle life, rapid charging/discharging rates, and high power density. However, their relatively low energy density remains a challenge. Extensive research has been conducted on electrode materials, particularly transition metal oxide (TMO) composites, to assess their value in the SC field. However, TMOs face significant challenges, such as limited electron and ion transport and poor electronic conductivity, which hinder their electrochemical performance in energy storage applications. Therefore, integrating carbon-based materials or conductive polymers presents a promising strategy for achieving higher energy density, enhanced specific power, and faster charging/discharging rates, thereby improving the overall efficiency of SCs. This review provides recent advancements in TMOs and their binary and ternary composites, emphasizing synthesis methods and their effects on electrochemical performance, while highlighting the potential of flexible and sustainable supercapacitors to meet increasing energy demands. Finally, the discussion on the current challenges and future outlook for these materials in supercapacitors as energy storage solutions will open avenues for further research and exploration.