(NaturalNews) The Toyota Corporation intends to develop a plug-in hybrid vehicle for its demonstration fleet by 2010, according to an announcement made by Chief Executive Officer Katsuaki Watanabe.The planned plug-in hybrids are already under development, with two prototypes currently undergoing demonstration tests by researchers at the University of California. But while existing prototypes operate with nickel-metal-hydride battery packs, Toyota aims for its new hybrids to be equipped with lithium-ion batteries.Lithium-ion batteries, already widely used in consumer electronics, provide more energy per unit weight than older nickel-metal-hydride batteries, and can store a charge for longer when not in use.Watanabe cautioned that while successful lithium-ion batteries have already been developed for hybrid electric automobiles, it is premature to assume that such batteries can be mass produced with existing techniques"As of today in the lab, the small volume of lithium-ion we have already developed is closer to the level we are satisfied with, but that is only in small quality," he said. "There is a huge difference between small volume and mass production of lithium-ion."The remarks were interpreted as a response to General Motors' (GM) alliance with battery maker A123, which has so far failed to deliver mass production of lithium-ion batteries.Toyota's other planned efforts in the area of fuel efficiency include the unveiling of new hybrid-only models in 2009, increased investment in the production of ethanol from wood waste, the expansion of a joint Panasonic-Toyota batter factory, the introduction of "clean diesel" V-8 versions of the Tundra pickup and Sequoia SUV and the sale of 1 million hybrid vehicles by 2012. In addition, Watanabe announced the company's intention to meet California's 35 mile per gallon fleet standard "well in advance" of the 2020 deadline.Unlike competitor GM, Toyota is conducting all of its research in-house, rather than in partnership with small or start-up companies. According to Watanabe, this will make technological development "faster and more efficient."