Glyoxal-based electrolytes in potassium-ion capacitors

Potassium-based energy storage systems demonstrate promising potential for use in high-power applications, such as potassium-ion capacitors (PICs). In this study, we present the use of an electrolyte containing 1,1,2,2-tetraethoxyethane (TEG) in combination with propylene carbonate (PC) and potassium bis(fluorosulfonyl)imide (KFSI) as electrolyte for PICs. We have shown that using this electrolyte and applying a designed test protocol, it is possible to realize PICs with good capacity and cycling stability. The high performance is possible due to the high-rate capability of the graphite electrodes in the proposed electrolyte. Subsequent analysis of the electrodes reveals both structural changes of the graphite electrode and changes in the chemical composition of the AC and graphite electrode surfaces. • Graphite electrode rate performance enhanced by cell compression and wetting. • Capacity of 182 mAh g −1 at 5 C for K + intercalation into graphite. • Glyoxal-based electrolyte for potassium-ion capacitor. • Change in electrode surface composition after cycling (determined by XPS).