Wednesday, March 21, 2012

No. 465: A new material for the positive electrode of lithium-ion battery with eight times higher charge and discharge efficiency (March 21, 2012)

Professor Yutaka Moritomo of Tsukuba University developed a material for the positive electrode of lithium-ion battery that can discharge in about one second. He applied the Prussian blue analog that allows many electrons at one time to the positive electrode. The new material can charge and discharge at eight times higher efficiency as compared with the existing material. Because the new material is inexpensive and hard to deteriorate, it opened up the way for an inexpensive lithium-ion battery. If optimal negative electrode and device are developed, a high-speed and large-volume charging will be available for mobile phones and electric vehicles.

The new material is a Prussian blue compound made up of iron, manganese, carbon, and nitrogen. It has a jungle gym structure with a grid interval of 0.5 nanometers. Because this grid interval has a width of about five lithium ions, it allows lithium ions goes in and out at high speed. In the experiment, a nanoparticle (with a particle diameter of 50 nanometers) is processed to a one-centimeter-square film and attached firmly to an electrode. After 0.01 milliampere was charged in eight minutes, it was discharged at a time. This generated current of 85 milliampere per gram, and the discharge time was merely 1.1 seconds. Because the new material is not an oxide, it did not deteriorate even after 30 times of charge and discharge. The professor told that the new material has huge potential, though it is necessary to solve the problem with heat generation in discharge to use it for battery.

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