Battery Electrode Materials with Omnivalent Cation Storage for Fast and Charge‐Efficient Ion Removal of Asymmetric Capacitive Deionization

Abstract Capacitive deionization (CDI) that engages porous carbon electrodes constitutes one of the well‐established energy‐efficient desalination methods. However, improvement in desalination performance, including ion removal capacity, ion removal rate, and charge efficiency remains requisite for a wide range of applications. Herein, an ion‐exchange membrane‐free asymmetric CDI is introduced by pairing a metal organic framework (MOF), namely, K0.03Cu[Fe(CN)6]0.65·0.43H2O and porous carbon. The exclusive intercalation of cations into the MOF prevents the reverse adsorption of co‐ions (anions), thus significantly improving ion removal capacity (23.2 mg g−1) and charge efficiency (75.8%). Moreover, by utilizing the advantage of the MOF that diverse mono‐ and divalent cations can be stored in the narrow redox potential range, the asymmetric CDI allows simultaneous capture of mono‐ and diva…