A fundamental understanding of the charge storage mechanism of electrochemical double-layer capacitors (EDLCs) requires an in-depth storage behavior investigation of independent ions (individual cations or anions) on the electrode surface. The direct in-situ observation for energy storage behavior of individual ions under realistic conditions remains challenge. Herein, in-situ monitoring the energy storage behavior of independent ions is realized with assistance of polymeric ionic liquids skillfully. Triangle cyclic voltammogram (CV) curves indicate that polymeric imidazole cations PVBIm⁺ with huge size cannot enter the active carbon pores upon charging, whereas only free anions can. The CV and electrochemical quartz crystal microbalance (EQCM) simultaneously detect ion adsorption/desorption during charging. It’s proposed that ion adsorption/desorption is governed by electrostatic attraction and repulsion of charged particles. PVBIm⁺ are adsorbed on the electrode surface due to ion adsorption mechanism during the negative polarization and have a small capacity contribution. Free anions contribute capacitance, their number entering the pore is determined by the interaction between polycaions and anions. Moreover, PVBIm(0.1)⁺ with higher polymerization degree may promote desorption of polycations and prevent further adsorption of anions at higher potential in positive polarization. This work not only observes the charging behavior of independent ions, but also reveals the relevant charging mechanism through EQCM, paving the way for panorama of EDLC.

对电化学双层电容器 (EDLC) 的电荷存储机制的基本了解需要对电极表面上的独立离子（单个阳离子或阴离子）进行深入的存储行为研究。在现实条件下对单个离子的储能行为进行直接原位观察仍然具有挑战性。在此，巧妙地借助聚合物离子液体实现了对独立离子储能行为的原位监测。三角形循环伏安 (CV) 曲线表明聚合咪唑阳离子 PVBIm ⁺具有巨大尺寸的离子在充电时不能进入活性炭孔，而只有游离阴离子可以。CV 和电化学石英晶体微天平 (EQCM) 在充电过程中同时检测离子吸附/解吸。有人提出离子吸附/解吸受带电粒子的静电吸引和排斥力控制。PVBIm ⁺在负极化过程中由于离子吸附机制吸附在电极表面，对容量的贡献很小。游离阴离子贡献电容，它们进入孔隙的数量由聚钙离子和阴离子之间的相互作用决定。此外，PVBIm(0.1) ⁺具有较高聚合度的可以促进聚阳离子的解吸并防止在正极化的较高电位下进一步吸附阴离子。这项工作不仅观察了独立离子的充电行为，还通过 EQCM 揭示了相关的充电机制，为 EDLC 的全景铺平了道路。