Agency of Industrial Science and Technology

Kashima-Kita, Electric Power Corporation

Ichiro Nakahara

Hiroko Kaneko

Ken Nozaki

Akira Negishi

Kenji Sato

A vanadium electrolytic solution containing highly concentrated and dissolved vanadium is produced by a method wherein a vanadium compound selected from the group consisting of ammonium metavanadate and vanadium pentaoxide is subjected to a reduction operation in the presence of inorganic acids. At this time, by repeating the addition of the concentrated inorganic acids and the vanadium compound, a tetravalent and pentavalent vanadium solution of 3.4 mol/l is obtained. In addition, the resulting vanadium electrolytic solution is electrolyzed, whereby tetravalent vanadium is reduced to be trivalent on the negative electrode and is oxidized into pentavalent vanadium on the positive electrode, and then pentavalent vanadium is reduced into tetravalent vanadium by a reducing agent to form a discharged couple of trivalent and tetravalent vanadium, and an electrolytic solution is obtained which is capable of being charge-discharged. This electrolytic solution can be used as the electrolytic solution for redox batteries using vanadium as the active material in both positive and negative electrodes.

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Kashima, Japan

Ichiro Nakahara