An Overview of Solid-Like Electrolytes for Supercapacitors

Supercapacitors with an electric double-layer design have attracted great attention in the recent years because they are promising energy storage devices for a number of applications, particularly for portable electronics and electric automobiles. They utilize the interface between the electrode and the electrolyte to store energy, resulting in energy storage devices with high power density but low energy density compared to batteries. To improve the performance and reduce the cost, researchers have made significant progress in increasing energy density, electrode voltage, and cycle life. The increase of the energy density is considered to be achieved mainly by increasing the effective specific interface between the electrodes and the electrolyte. Various electrodes with porous structure have been attempted to increase the specific surface area. The increase of electrode voltage is realized primarily via the change of liquid electrolytes to gel, solid and composite ones. In this overview, they are summarized as solid-like electrolytes. This paper reviews the materials adopted and the processing methods developed for solid-like electrolytes, as well as the general characteristics of supercapacitors employing such electrolytes.