Metal‐Ion Capacitors with Anion Intercalation Process

The advancement of the modern world demands high‐performance electrical energy storage devices such as metal‐ion capacitors and dual‐ion batteries, and they receive much attention recently with the merits of cost‐effectiveness, safety, environmental friendliness, and high operating voltage. This work emphasizes the metal‐ion capacitors (Li+, Na+, and K+) based on the dual‐carbon combination in which anion intercalation endorses the Faradaic reaction and cation involves in the non‐Faradaic process, promising for greater energy density. The role of graphite, anion graphite intercalation compounds, and the information about the megalo‐capacitance capacitor are first discussed. Subsequently, various influencing factors such as the effect of solvent, electrolyte, conducting salt, cations, and anions affecting the intercalation process are debated in detail. In addition, recently emerging various metal‐ion capacitors based on the anion intercalation process are also reviewed. The major challenges present in the development of the anion‐based hybrid capacitor are finally evaluated and an assessment to fulfill the goals for efficient energy storage is provided