Energy efficiency of neptunium redox battery in comparison with vanadium battery

T. Yamamura, N. Watanabe, Y. Shiokawa

Research output: Contribution to journalConference articlepeer-review

27 Citations (Scopus)


A neptunium ion possesses two isostructural and reversible redox couples (Np3+/Np4+ and NpO2+/NpO 22+) and is therefore suitable as an active material for a redox-flow battery. Since the plastic formed carbon (PFC) is known to show the largest k0 values for Np(IV)/Np(III) and Np(V)/Np(VI) reactions among various carbon electrodes, a cell was constructed by using the PFC, with the circulation induced by bubbling gas through the electrolyte. In discharge experiments with a neptunium and a vanadium battery using the cell, the former showed a lower voltage loss which suggests a smaller reaction overvoltage. Because of the high radioactivity of the neptunium, it was difficult to obtain sufficient circulation required for the redox-flow battery, therefore a model for evaluating the energy efficiency of the redox-flow battery was developed. By using the known k0 values for neptunium and vanadium electrode reactions at PFC electrodes, the energy efficiency of the neptunium battery was calculated to be 99.1% at 70 mA cm-2, which exceeds that of the vanadium battery by ca. 16%.

Original languageEnglish
Pages (from-to)1260-1266
Number of pages7
JournalJournal of Alloys and Compounds
Publication statusPublished - 2006 Feb 9
EventProceedings of the Rare Earths'04 in Nara, Japan -
Duration: 2004 Nov 72004 Nov 12


  • Energy efficiency
  • Neptunium battery
  • Redox-flow battery
  • Vanadium battery

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry


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