Limitations and Recent Advances in High Mass Loading Asymmetric Supercapacitors Based on Pseudocapacitive Materials

Abstract

Supercapacitors (SCs) have many advantages such as high power density, long cycle life, and low maintenance cost. However, the limited energy density has been a key barrier that critically hinders the practical applications of SCs. Asymmetric supercapacitors (ASCs) based on different positive and negative electrodes offer the possibility of increasing the energy density, but they are still not good enough. One way of further increasing their energy density is to increase the mass loading of the electrodes. However, it is still challenging to achieve high mass loadings without sacrificing power density. This review provides the current state of the art regarding high mass loading transition metal oxides-based ASCs and their electrochemical properties. Emphasis is given to the recent progress in manganese and nickel-based high mass loading ASCs. Their electrochemical performances are comprehensively discussed and the observations are summarized in an attempt to accelerate the development of next-generation energy storage devices.