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GS Yuasa Developing 25 Ah Li-ion Iron Phosphate Cell

GS Yuasa, the provider of the LEV50 Li-ion cell (earlier post) used in the battery pack for the i-MiEV, is developing a 25 Ah lithium iron phosphate (LFP) prototype, said Dr. Masanori Kitamura from GS Yuasa’s Corporate Strategic Planning group in a presentation at the Advanced Automotive Battery Conference 2009 (AABC).

Dr. Kitamura is also a director of Lithium Energy Japan, GS Yuasa’s joint venture with Mitsubishi.

The LEV50 cell going into the i MiEV pack is a 50 Ah, 3.7V cell using a mixed LMO/NMC cathode material with a hard carbon anode. The combination offers a specific energy of 109 Wh kg-1, and energy density of 218 Wh L-1.

In his presentation at AABC in 2008, Kitamura noted that GS Yuasa was beginning work on a 50 Ah LFP cell; the 25 Ah prototype is an evolution of the work focused on a practical application. The cathode material used is a carbon-loaded LiFePO4 combined with a graphite anode. The carbon loading improves the high-rate discharge capacities by about 25%.

The cell is showing densities greater than 182 Wh L-1 and 81.3 Wh kg-1, with a flat voltage profile.



I suppose we may see this technology with Honda vehicles as well, and not just the Mitsubishi i-MIEV, since they also have a partnership with Yuasa.


A scientist at Yuasa did some of the original work to create NiMH technology. They have been in the battery business a long time, so if they say that they have this, I tend to believe them. Lithium will make progress, but the cost and life span need to be improved to get them in wide spread use for personal transportation.

Raymond Bonnaterre

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Quality in carbon coating is a key point to prevent, inside the electrode, spot local high current density, inhomogeneous cristallization and to get longer battery cycle life and higher discharge voltage. Japanese battery industry subcontractors are surely working a lot on the subject! A very sophisticated positive material is definitively needed to define a long life LiFePO4 battery.

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