Batteries still a challenge to electric dream

Electricity is the key to sustainable mobility, says Toyota, but batteries are still the must-improve technology. That's the key tenet behind a large slice of the world's largest car company's research and development programs, according to Toyota's Project General Manager R&D Management Division, Yukata Matsumoto.

Matsumoto delivered an overview of Toyota's Research and Development Activities for Realising Sustainable Mobility to Australian and assembled overseas media in Tokyo yesterday, on the eve of the Japanese megapolis' biennial motor show.

Though he outlined in very general terms the company's desire to pursue parallel development of existing combustion technologies (see separate story) as well as fuel cell, electric, hybrid and plug-in hybrid vehicles, one of the key points was the need to improve battery technology. Specifically the 'energy density' of existing and future battery systems... Put simply, increasing how much power can be squeezed into the storage units.

Matsumoto's presentation included the energy density targets proposed by METI, Japan's Ministry of Economy, Trade and Industry for automotive EV batteries for 2010, 2015 and 2020. The targets set an increase of almost threefold to the energy density of the very best batteries currently in production.

In the case of Toyota's iQ-based EV (pictured) set for US introduction in 2012, the increase would equate to a boost in range from 80 to 200km. While Matsumoto believes such a range would be acceptable to most consumers, he is honest about the likelihood of Toyota meeting the 2020 target density.

"It is very challenging," he said through an interpreter. "We don't know whether it will be done."

Currently, Toyota uses nickel metal hydride batteries in its various hybrid models -- including the third generation Prius. A new plug-in version of the Prius to be launched at the Tokyo show this week features an upgraded lithium ion pack. Toyota's EV concept vehicles also use LiOn cells

Matsumoto's team defines the peak energy density of existing battery systems (including lithium-ion) at around six times the value of the nickel metal hydride cells used in vehicles like the current Prius. This equates to a range in the region of 600-700km.

But the ultimate target towards which Toyota's advanced engineering teams strive is a theoretical battery energy density level defined as a 'Sakichi Battery'.

Named after Sakichi Toyoda, the founder of Toyota and the inventor of Japan's first power loom, the Sakichi Battery is the term given to breakthrough technology that will deliver a battery that has a theoretical range in orders of magnitude above current cells.

"Think of it as a 'dream' battery," said Matsumoto. "On the basis that one charge would give you enough energy to drive around the world."

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