In ionic liquid based electrical double layer, crowding state is used to explain the unique shape of the differential capacitance curve. However, the differential capacitance values are still significantly underestimated and an impractically high electrode potential is required to observe the crowding state in simulations. In this study, based on the electrode charge distribution obtained from joint density functional theory calculations, we successfully predict the differential capacitance curve with both shape and magnitude correct. At the same time, we find a new type of ionic liquid crowding state at low potentials within the electrochemical window, which is induced by adsorption state transition of organic ions. These results provide new insights in understanding ionic liquid at electrified interfaces.

在基于离子液体的双电层中，拥挤状态被用来解释微分电容曲线的独特形状。然而，差分电容值仍然被严重低估，并且需要不切实际的高电极电位来观察模拟中的拥挤状态。在这项研究中，基于联合密度泛函理论计算得到的电极电荷分布，我们成功地预测了形状和大小都正确的微分电容曲线。同时，我们在电化学窗口内发现了一种新型的离子液体在低电位下的拥挤态，这是由有机离子的吸附态转变引起的。这些结果为理解带电界面的离子液体提供了新的见解。