Doping of rare earth elements: Towards enhancing the electrochemical performance of pseudocapacitive materials

The emerging challenges of global warming have instigated people to produce and store renewable energy. Among various energy storage devices, the supercapacitor is an advanced energy storage device that has been used in many crucial applications to provide the necessary power. As a result, in the last couple of decades, pseudocapacitive materials such as metal oxides and conducting polymer-based electrode materials have shown remarkable electrochemical performance. However, the performance of bare pseudocapacitive materials is hindered due to their limitations, such as low conductivity, low surface area, poor electrochemical activity, etc. These limitations can be addressed by doping as it is an effective way of altering various physicochemical properties, such as crystal structure, surface morphology, specific surface area, electronic conductivity, and chemical stability of the host material, which ultimately enhances the electrochemical performance of the doped material. Therefore, in this review, we have discussed the effect of rare earth element doping in pseudocapacitive material. The doping strategy altered the crystallographic parameters, surface morphology, specific capacitance, and cyclability. In addition, various methods employed for doping rare earth elements in pseudocapacitive materials are summarized. Finally, the prospects of rare earth element doped electrode materials in current supercapacitor development are discussed.