The plan, the Nikkei says, is for Toyota and production partner Panasonic to build a new production line that will be able to make 200,000 li-ion batteries a year (why does that number sound so familiar?). The companies will spend about 20 billion yen (US $194 million) on the project. There's no way Toyota can put li-ion cells in all of its hybrids from that one line, though, since the company sells over a million hybrids a year.
Lithium-ion batteries are smaller, lighter and more energy dense than NiMH ones, but they're also more expensive. They are in widespread use in plug-in electric vehicles from a variety of auto manufacturers. Toyota is also working on future battery technologies, like solid state packs.