Hydrogen Bond Interaction in the Trade‐Off Between Electrolyte Voltage Window and Supercapacitor Low‐Temperature Performances

Liquid electrolyte determines the voltage window and extreme working temperature of supercapacitors. However, the effect of weak interaction between electrolyte species on voltage window and low-temperature capacitive performance is unclear. Herein, an electrolyte model system with increasing H-bond interaction was constructed to clarify this concern. The results indicated that strong H-bond interaction was positively correlated with the number of hydroxyls, which was beneficial to expand voltage window, but deteriorated rate performance; weak H-bond improved low-temperature performance. Supercapacitors with an optimized electrolyte presented high voltage and good low-temperature performance; even at -40 °C, the maximum energy density could be maintained at 7.0 Wh kg^-1 (>80 % retention relative to at -20 °C). This study revealed the mechanism of the influence of the H-bonds on electrolyte voltage window and anti-freezing capability and provided a new insight for the design of electrolytes with both high working voltage and low-temperature performance.