Toyota admits lithium ion battery technology is still too hazardous to use in its production cars despite GM announcing earlier this year that it expects to have a plug-in hybrid vehicle with lithium batteries by the end of the decade. The Japanese giant doesn’t want to rush out products with lithium batteries and then see them fail once they've left the showroom floor.

The biggest factor holding it back is safety fears, revealed Toyota's executive vice president for R&D Kazuo Okamoto during an interview with Automotive News. Instead, engineers will concentrate on improving the efficiency of current nickel-metal hydride technology. Lithium ion batteries are smaller and lighter than nickel-metal hydride but they tend to overheat and can even catch on fire.

Okamoto wasn’t willing to give a timeline for the introduction of the new batteries, explaining that there are still a lot of problems to solve.

Though lithium-ion batteries are the power source of choice for a new generation of plug-in hybrids, Toyota is still focusing on rolling out the new electric vehicles despite the expected delays in battery technology. The carmaker has just announced the formation of a new partnership with power utility Electricite de France SA (EDF) to develop electricity infrastructure for plug-in vehicles.