Most Modern Supercapacitor Designs Advanced Electrolyte and Interface

Electrolyte plays a key and significant role in supercapacitors. The interaction of an electrode and a chosen electrolyte has a significant effect on the parameters., i.e., ionic conductivity, stable potential range, and charge transfer coefficient, therefore determining the corresponding performance. The captivating interface between electrode and electrolyte is also pushing the intensive research. In this chapter, we focus on two kinds of electrolytes, including water-in-salt electrolytes and redox-ionic liquid. Water-in-salt electrolyte is drawing continuous attention thanks to the formed hydrophobic layer on the positive electrode and solid electrolyte interphase (SEI) on the negative side, preventing water splitting. On the other side, redox-ionic liquid, taking advantage of the broad and stable working window, on the interface, the redox shuttle passes and targets the suitable electrode bulk, leading to redox reactions to highlight capacitance and energy.