Fig 1: The prototype Li-ion rechargeable battery for hybrid vehicles that was exhibited. On the lower left is a 3.8Ah cell measuring 251 x 144 x 3.4mm and weighing 211g. On the lower right is a module composed of eight cells stacked on top of each other. Above is a battery pack composed of 10 modules.
Fig 1: The prototype Li-ion rechargeable battery for hybrid vehicles that was exhibited. On the lower left is a 3.8Ah cell measuring 251 x 144 x 3.4mm and weighing 211g. On the lower right is a module composed of eight cells stacked on top of each other. Above is a battery pack composed of 10 modules.
[Click to enlarge image]
Fig 2: Crystal structure diagrams of positive electrode materials in Li-ion rechargeable batteries. On the left is the layered structure of an existing positive electrode material such as cobalt. On the right is the spinel structure of a manganese-based material.
Fig 2: Crystal structure diagrams of positive electrode materials in Li-ion rechargeable batteries. On the left is the layered structure of an existing positive electrode material such as cobalt. On the right is the spinel structure of a manganese-based material.
[Click to enlarge image]

Nissan Motor Co Ltd, NEC Corp and NEC Tokin Corp announced the automotive Li-ion rechargeable battery production plan for their joint-venture company, Automotive Energy Supply Corp (AESC), May 19, 2008.

AESC will invest ¥12 billion (US$116 million) over the next three years and set up the production line at Nissan's Zama facility. The company aims to manufacture 13,000 batteries (1,600,000 cells) annually for hybrid and electric vehicles by fiscal 2009. It also plans to expand the production capacity to 65,000 units by fiscal 2011.

AESC was established as a fifty-fifty joint venture company between Nissan and the NEC Group in April 2007. In line with the launch of AESC's full operations for the automotive business, Nissan decided to hold the majority of the shares at 51%, while NEC and NEC Tokin will hold shares of 42% and 7% respectively. The capital was also significantly expanded from ¥245 million to ¥1.495 billion (total capital: ¥2.99 billion).

AESC's Li-ion rechargeable batteries will be first employed in Nissan's small forklift slated for release in 2009 to replace the existing zinc batteries. This will be followed by Nissan's electric and hybrid vehicles, which will be introduced in the US and Japan in fiscal 2010 (Fig 1).

Asked whether the company is planning to supply the battery to other manufacturers, Masahiko Otsuka, president of AESC replied to the reporter as follows, implying the possible sales channel.

"We have a diversity of customers although we cannot detail the proportion."

In fact, the company announced that it will provide the battery to the projects currently being contemplated by Project Better Place to construct the electric vehicle infrastructure in Denmark and Israel.

At a press conference, Otsuka also cited the following as three strong points of AESC's Li-ion rechargeable batteries: (1) Greater safety resulting from manganese used for the positive electrode, (2) possibility of lower cost due to the laminated structure and (3) higher reliability based on the automotive compatibility already confirmed through Nissan's experiences.

With regard to the point (1), the Mn-based positive electrode material has a robust structure called "spinel structure" (Fig 2), in contrast to the existing materials using cobalt, etc, which have a layered structure, Otsuka said. Therefore, the manganese-based material is free from thermal runaway* because the crystal structure is stable even in the state of overcharge, he said.

*Thermal runaway is a phenomenon to cause fire or smoke due to the reaction between the organic electrolyte and hydrogen, which is generated by the deformation of crystal structure occurring when the material is heated to a temperature higher than one hundred and several tens degrees Centigrade due to overcharge.)

Asked how the AESC confirmed the safety of the battery, Otsuka said, "Our battery passed various kinds of safety tests and we also confirmed the battery's safety through the field tests conducted for seven to eight years from 2000."

One of the problems of manganese-based Li-ion rechargeable batteries is the energy density, which is lower than that of batteries with other positive electrode materials. But the company announced that the present energy density of its battery for electric vehicles is 160Wh/kg.

AESC seems to be making progress in improving performance, considering the fact that the density announced at a last year's press meeting was only "90Wh/kg." But the company did not unveil the target performance.

"We plan to reduce the cost through the economies of volume production and technical improvements though I cannot discuss our strategy in detail because a dozen companies are competing fiercely against each other," Otsuka said, revealing the company's views on cost reduction.

"It is a tough time with rising material prices, but we hope to offer products at a competitive price," he said.