The development of Vanadium rechargeable batteries

By Yamato Energy Laboratory for Yamato Energy

The development of Vanadium rechargeable batteries

Introduction

 Yamato Energy Laboratory has studied extensively for the development of vanadium rechargeable batteries. The purpose is to develop a secure and high energy density battery for hybrid automobiles, to develop an eco-battery replacing the lead battery and to develop a large scale battery for smart grid. We are willing to supply these technologies in the world.

Since vanadium possesses four different oxidation states, rechargeable batteries can be made using the oxidation-reduction reactions between these oxidation states. The redox flow battery in sulfuric acid solutions has been long known. However, this battery has a merit of using vanadium metal only, but has also a demerit of the decrease in functional activity due to the precipitations of vanadium salts. The development of vanadium battery, particularly for a complete solid battery, is fundamentally difficult until sulfuric acid is used.

Under the present circumstances, we have studied vanadium batteries based on a new concept and achieved the following development:

  1. Development of a secure solid battery for hybrid automobiles
  2. Development of an echo and light battery replacing the lead battery
  3. Development of a large scale battery for smart grid

Vanadium Complex Solid-State Rechargeable Battery

 Yamato Energy Laboratory has studied on vanadium batteries based on a new concept and found that a complete solid battery can be made using some vanadium complexes, where the complexes are pressed to form pellets. This is the first vanadium solid battery in the world, and we call vanadium complex solid-state rechargeable battery hereafter. Like as the lithium ion battery, the pellets should be moistened by electro conductive solvents. It is most characteristic that both water and non-aqueous solvents can be used for moistening. The electromotive force of vanadium complex solid battery is higher than 2V, which is smaller than that of the lithium ion battery. However, unlike the lithium ion battery, the security can be guaranteed under severe conditions in the vanadium complex solid-state battery. As compared with the electro motive force of the nickel hydrogen battery of 1.2 V, the vanadium complex solid battery has a feasible possibility for the use of hybrid automobiles

.Vanadium (III) complex (left) and Vanadium (IV)complex (right)

Vanadium Complex Liquid-State Rechargeable Battery

In order to solve the problem that vanadium salts precipitate in the conventional vanadium redox flow battery in sulfuric acid solutions, we have applied the vanadium complex battery to solutions and succeeded to make a new battery, called as a vanadium complex liquid-state rechargeable battery. The solutions used are non-aqueous solvents instead of sulfuric acid. It should be noted that the solutions in both a cathode and an anode are stable after charged under atmospheric conditions indicating the stable storage of electricity for long time. The electromotive force is about 1.5V, which is considerably smaller than that of the solid vanadium battery. This can be explained reasonably as considered that the whole vanadium complexes involving a ligand contribute to the redox reactions.

FTP Battery

In the vanadium complex rechargeable battery, the same vanadium(IV) complex can be used in both a cathode and an anode. We call this battery as a FTP Battery hereafter. This is attributed to the fact that the reduction rate from vanadium (IV) to vanadium(III) complex is extremely fast as compared with that of the same reaction in sulfuric acid solutions. The use of only one active material has a merit of simplifying the manufacturing processes.

Conclusion

The vanadium complex solid battery should be made economically considering the costs of materials and the simple structure as compared with the lithium ion battery and the nickel hydrogen battery. The energy density of vanadium complex battery will be lower than that of lithium ion battery, but be higher than that of nickel hydrogen battery considering its larger electromotive force. Since the safety is always secured under severe conditions, the vanadium complex solid battery is expected to be used in hybrid automobiles in the future. At moment, a complete method of storing a large amount of electricity does not exist. Since vanadium complexes are very stable after charged under atmospheric conditions, the vanadium complex liquid-state rechargeable battery gives a feasible possibility in the storage of a large amount of electricity.

In view of the global environment, the use of lead battery should be altered in the future. The vanadium complex liquid-state rechargeable battery will be one of the the alternative of the lead battery, because of its simple structure like as the lead battery.

Research Group

Yamato Energy Laboratory.
CEO FUJIMOTO, Yoshihisa
Director TOMIYASU, Hiroshi Dr.
(Emeritus Professor of Tokyo Institute of Technology)
Senior Researcher PARK, Yoon-Yul Dr.
Invited Researcher KIMURA,, Mototetsu Dr.
Coworkers
Naraken Goudou Saiseki Co.Ltd
President FUJIMOTO, Yoshito
Managing Director FUJIMOTO, Takeya
Tokyo Institute of Technology, Research laboratory for Nuclear Reactors
Associate Professor TSUKAHARA, Takehiko, Dr.
Tokai University, Faculty of Engineering
Associate Professor ASANUMA, Noriko, Dr.

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