Insight into the Camel‐to‐Bell Transition of Differential Capacitance in Ionic Liquid‐Based Supercapacitors

Abstract Understanding ionic liquid (IL)‐electrode interface is of great significance to the design of electrochemical systems. Herein, the electrical double layer (EDL) structure and charging process of the supercapacitor with ILs were investigated by engineering the cation‐anion and IL‐electrode interaction through molecular dynamics simulations coupled with the constant potential method. A camel‐to‐bell shape transition of differential capacitance was identified when the cation‐anion or IL‐electrode interaction decreased, manifesting the sensitive responses of EDL structure and charging mechanism to the varying interactions. Moreover, the identified camel‐to‐bell transition could lead to the rise of differential capacitance and energy density in the low working voltage. These findings can help guide the molecular design for high‐performance IL‐based supercapacitors and other electrochemical devices where the IL‐electrode interfaces are crucial.