Polyaniline, binary transition metal oxide and their nanocomposites as high-performance electrode materials for supercapacitor applications

Supercapacitors (SCs) have emerged as promising energy storage devices owing to their superior capacitance, greater power density and higher cycling stability. Polyaniline (PANI) is a potential electrode material for SCs applications due to its easy fabrication, excellent specific capacitance and high conductivity. However, its small life cycle limits its application in device fabrication. Therefore, PANI composites have been designed with binary transition metal oxides (BTMOs) which possess admirable structural stability, remarkable electronic conductivity and inherent oxygen vacancies. Moreover, decorating PANI surface with BTMOs depicts a better electrochemical performance which ought to be explored. This review focuses on a detailed description of PANI, BTMOs and PANI/BTMOs nanocomposites including their structures, conduction mechanisms, electronic and electrochemical properties and recent rational design and fabrication processes. Further, a systematic charge storage mechanism for PANI/BTMOs has also been articulated in relation to the SCs. Moreover, the effect of PANI/ BTMOs electrodes' morphology on the supercapacitive performance and process parameters has been elucidated. Finally, we discussed the overlooked challenges and aimed to provide practical solutions for viable PANI/BTMOs based SCs.