Abstract: Performance improvers and formulations for energy storage devices are disclosed. The performance improvers include halogenated aromatic heterocycle compounds that may be utilized to improve the performance of energy storage devices (e.g., capacitors) operating at voltage above 3 V (e.g., 3.2 V).

Abstract: Disclosed is a capacitor that is not easily degraded to stably maintain the performance for a long time. The electrochemical capacitor includes a first electrode provided in a rolled sheet form and having active material layers coated on both surfaces thereof; a second electrode provided in a rolled sheet form at an outer side of the first electrode to face the first electrode and having active material layers coated on both surfaces thereof; and a separator interposed and rolled between the first electrode and the second electrode, wherein at least a portion of an outermost layer of the first electrode is exposed to the outside.