Sodium- and Potassium-Hydrate Melts Containing Asymmetric Imide Anions for High-Voltage Aqueous Batteries

Qifeng Zheng, Shota Miura, Kasumi Miyazaki, Seongjae Ko, Eriko Watanabe, Masaki Okoshi, Chien Pin Chou, Yoshifumi Nishimura, Hiromi Nakai, Takeshi Kamiya, Tsunetoshi Honda, Jun Akikusa, Yuki Yamada, Atsuo Yamada*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

75 Citations (Scopus)


Aqueous Na- or K-ion batteries could virtually eliminate the safety and cost concerns raised from Li-ion batteries, but their widespread applications have generally suffered from narrow electrochemical potential window (ca. 1.23 V) of aqueous electrolytes that leads to low energy density. Herein, by exploring optimized eutectic systems of Na and K salts with asymmetric imide anions, we discovered, for the first time, room-temperature hydrate melts for Na and K systems, which are the second and third alkali metal hydrate melts reported since the first discovery of Li hydrate melt by our group in 2016. The newly discovered Na- and K- hydrate melts could significantly extend the potential window up to 2.7 and 2.5 V (at Pt electrode), respectively, owing to the merit that almost all water molecules participate in the Na+ or K+ hydration shells. As a proof-of-concept, a prototype Na3V2(PO4)2F3|NaTi2(PO4)3 aqueous Na-ion full-cell with the Na-hydrate-melt electrolyte delivers an average discharge voltage of 1.75 V, that is among the highest value ever reported for all aqueous Na-ion batteries.

Original languageEnglish
Pages (from-to)14202-14207
Number of pages6
JournalAngewandte Chemie - International Edition
Issue number40
Publication statusPublished - 2019 Oct 1


  • aqueous batteries
  • asymmetric imide anion
  • electrochemistry
  • hydrates
  • potential window expansion

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)


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