Review on Current Progress of MnO2-Based Ternary Nanocomposites for Supercapacitor Applications

Manganese dioxide (MnO2) has proved itself as a popular pseudocapacitive material with low fabrication cost, high availability, low toxicity, and improved handling safety compared to many other inorganics or carbon-based systems existing in the market. However, the specific capacitance reported to date has been far inferior to that of the theoretically predicted value (ca. 1370 Fg(-1)), which is mainly attributed to the issues associated with poor conductivity, nanostructure agglomeration, low porosity, rapid electrolyte-mediated dissolution, and so forth, which have considerably limited its commercial effectiveness. Thus, to bring about improvement in the electrochemical performance of MnO2-based supercapacitors, novel designs of MnO2 nanomaterials through composite formations with other substances, such as nanocarbons, conducting polymers or inorganic materials, namely metal oxides and sulfides, have been comprehensively explored. Extensive studies on these MnO2 binary nanocomposites revealed significant improvement in the electrochemical features compared to pristine phases; nevertheless, the achieved state is still far below practicability. Hence, scientists have opted for MnO2-based ternary nanocomposites achieved by blending appropriate proportions the three components (MnO2 nanostructures being one of the constant components) that would promote synergism to attain suitable dimensions, crystallinity, crystal structure, conductivity, mass loading, and electrolyte selectivity so as to confer superior capacitance, charge transfer kinetics, better utilization of electroactive materials, energy and power densities, as well as improved mechanical stability and environmental adaptability. Herein, recent developments and advancements in the research of various MnO2-based ternary nanocomposites employed for supercapacitor applications have been discussed and are compared with binary analogs with special emphasis on correlating their composition, morphology, and the electrochemical properties that are noticeably modified upon introduction of the third component. The associated challenges encountered in their progress toward commercialization and the probable ideas of persuading better strategic designs of these ternary systems for high-performance supercapacitor applications have also been delineated.

Automated summary

Manganese dioxide (MnO2) has shown potential as a pseudocapacitive material, with efforts to improve its electrochemical performance through novel designs of nanomaterials and ternary nanocomposites. However, the achieved state is still below practicality, leading to further exploration in blending different components for synergistic effects in achieving superior capacitance and charge transfer kinetics. Recent research focuses on overcoming challenges in commercializing these MnO2-based ternary systems for high-performance supercapacitor applications.