Unlocking High‐Performance Supercapacitor Behavior and Sustained Chemical Stability of 2D Metallic CrSe2 by Optimal Electrolyte Selection

Supercapacitors are energy storage devices with the ability to rapidly charge and discharge, making them a valuable complement to battery systems. To maximize their fast‐charging capabilities, identifying materials and methods to enhance their energy density is crucial. In this work, we carried out a comprehensive study of an emerging 2D dichalcogenide, CrSe2, as a supercapacitor material. We demonstrate that CrSe2 can be obtained at ambient temperature through deintercalation of a relevant KCrSe2 precursor using a 0.5 M solution of I2 in acetonitrile. Although CrSe2 decomposed in 1 M KOH, it was found to be chemically stable in common electrolytes such as H2SO4, Li2SO4, and Na2SO4. Despite low surface area CrSe2 reached a specific capacitance of 27 F g−1 in 1 M H2SO4 and, thus consistently outperformed high surface carbon black. Computational studies suggested that the metallic conductivity of CrSe2 was likely the primary factor contributing to the superior performance of this 2D chalcogenide over high surface carbon analogues.