Study of RuO2- and MnO2-based electrode materials and their performance review in conjunction with PANi for supercapacitor applications

Supercapacitors have emerged today as a compelling choice in the realm of renewable and clean energy storage. They possess several outstanding features such as high-power density, quick charging/discharging, long-cycle life, safety, and environment friendliness. These features make them an attractive option for a wide range of applications, including renewable energy systems, transportation, consumer electronics, energy harvesting, medical, aerospace, and defense. However, supercapacitors suffer from some limitations, such as low-energy density compared to alternative energy storage technologies like lithium-ion batteries. Through meticulous selection and optimization of electrode materials, it is possible to tackle this challenge while simultaneously enhancing the energy storage capacity and preserving their other favorable characteristics. Thus, the choice of electrode materials plays a decisive role in determining the overall performance of supercapacitors. In this review paper, an elaborate description of the technologies, operational principles, and recent progress behind the two significant transition metal oxides, namely RuO₂ and MnO₂, along with their integration with PANi, a crucial conducting polymer, employed as electrode materials in supercapacitors, are presented. The performance of these nanocomposite electrode materials with a primary consideration on their binary forms has been analyzed and reviewed by the parameters like energy density, power density, specific capacitance, cyclic performance, and rate capability. Detailed discussion is made regarding the structure of the materials prepared using varied synthesis processes with special focus on the morphology and capacitance values, future prospects, and how do they align with the desired performance attributes.