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

Seungyeon Choi, Barsa Chang, Seoni Kim, Jiho Lee, Jeyong Yoon, Jang Wook Choi

Research output: Contribution to journalArticlepeer-review

118 Scopus citations


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 divalent cations, thus achieving omnivalent cation removal. Moreover, cations are intercalated in the hydrated forms without a discrete phase transition of the host structure, facilitating rapid desalination by reducing the desolvation energy penalty, which results in a high ion removal rate of 0.24 mg g−1 s−1. This study offers a new design principle in CDI: the integration of a crystal structure with large ionic channels that enable hydrated intercalation of multivalent ions in a fast and exclusive manner.

Original languageEnglish
Article number1802665
JournalAdvanced Functional Materials
Issue number35
StatePublished - 29 Aug 2018

Bibliographical note

Funding Information:
S.C. and B.C. contributed equally to this work. J.W.C. acknowledges financial support from a National Research Foundation of Korea grant (NRF-2018R1A2A1A19023146 and 2017M1A2A2044477).

Publisher Copyright:
© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim


  • asymmetric capacitive deionization
  • desalination
  • ion removal efficiency
  • ion-exchange membranes
  • metal organic frameworks


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