The news of several new Toyota battery plants under construction was thought to presage the push for a 100% hybrid lineup, but the latest comments by a senior executive indicate the new plants are necessary just to keep up with current demand levels. Adding even more capacity and moving toward higher-capacity lithium-ion batteries are the next steps for the world's biggest hybrid producer.

Hybrids have a green image that is also increasingly popular, but batteries are among the dirtier aspects of modern auto production. Toyota has been working to improve the ecological soundness of its production process, but hasn't yet been able to make battery production greener because of the high demand. Once the company has enough capacity to comfortably produce the number of batteries it needs, however, attention will shift to making their production more environmentally friendly, reports The Detroit News.

The move toward the next-generation of batteries, lithium-ion units for hybrids, will be made in conjunction with Matsushita. That will mark the beginning of Toyota's transition away from nickel-metal hydride batteries, considered 'last-generation' technology by many in the industry, but still at the heart of the Prius and Toyota's other hybrids.

The two plants currently being built in Japan are expected to build more nickel-metal hydride batteries, although a new research department is working on a battery that will supposedly beat lithium-ion batteries, which could explain why Toyota hasn't been quick to adopt the newer type of battery.