Safe, long life, and high energy density aqueous lithium-ion battery developed by Yokohama National University

The research group of Professor Naoaki Yabuuchi of Yokohama National University Faculty of Engineering collaborated with Technical University of Munich, Germany, the National Institute for Materials Science and Sumitomo Electric Industries. They employed a nonflammable and safe water-based electrolytic solution, and a previously developed rock-salt-type molybdenum-based oxide negative electrode material to develop a safe and secure lithium-ion battery that has the same long life as a conventional lithium-ion battery that uses a flammable organic solvent.

Fire accidents caused by the ignition of a lithium-ion storage battery have become a major problem. Due to this issue, it is crucial that an aqueous lithium-ion battery using nonflammable water as an electrolytic solution be put into practice as a safe next-generation battery. However, since water is decomposed during charging, it is not possible to achieve both high energy density and long life, which are the requirements of a practical battery.

The research group is working on the development of rock-salt type molybdenum oxide material; they showed that by using this material, it possible to suppress the decomposition of water and achieve a life equivalent to that of a conventional lithium-ion battery. Despite being a water-based battery, it achieved 100 Wh/Kg at a high energy density, and proved that it can maintain 70% or more of the initial capacity even after 2000 cycles. Professor Yabuuchi reported that the energy density and service life of the developed lithium-ion battery can be increased if the electrode surface can be further stabilized and decomposition of water can be suppressed. These results are expected to be applied to ultra-large battery storage systems that enable the storage of natural energy."

■ Electrolytic solution: A solution that facilitates transport of ions between the positive and negative electrodes during the charging and discharging of the battery.