Electrochemical capacitors（also known as supercapacitors）

as a kind of energy storage device with high power density

long cyclic life and excellent stability

has attracted more and more attentions in recent years. Solid-state or quasi-solid-state supercapacitors can be widely applied in flexible electronics

flexible energy storage devices

wearable devices

and other areas due to their excellent mechanical flexibility

low volatility and flammability

easy assembly and molding. We thus introduce the advantages and configurations of solid-state supercapacitors. The solid-state electrolytes

which include the polymer gel electrolytes and the inorganic solid-state electrolytes

are introduced respectively. According to the different solvents

polymer gel electrolytes can be divided into hydrogel electrolytes

organogel electrolytes

and ionogel electrolytes. Among them

hydrogel electrolytes have been widely investigated due to their superior biocompatibility and good electrochemical performance. The inorganic solid-state electrolytes have relatively poorer electrochemical performance compared to the polymer gel electrolytes

they still play an important role in some specific areas such as satellite electronics because of the bone dry property. Lastly

different types and the characteristics of redox additives in solid-state electrolytes are introduced. It is noticed that the inorganic redox additive is a good option to increase the energy density as well as the power density of solid-state supercapacitors.