Toyota doesn’t really have much of a penchant for Li-ion battery technology, instead trusting its NiMH battery technology developed in-house.
True, the Toyota RAV4 EV uses Li-ion, but the entire drive system was developed by Tesla Motors. The Toyota Prius Plug-In, to date, is the only other model to use sourced Li-ion battery technology.
Li-ion is more energy-dense than NiMH, but Toyota has been developing their own NiMH replacement, and the next-generation solid state and lithium-air [LiO2] battery technology being developed by Toyota looks to take Toyota further than all the others.
Other battery technologies have their advantages, but companies developing lithium-iron phosphate [LiFePO4] and others have gone under trying to bring them to market. At least Toyota has the rest of their business to keep them afloat while they develop new battery technology. Toyota’s next-generation solid state battery technology could be commercialized by 2020, realizing an increase in energy density two or three times that of Li-ion with liquid electrolyte.
Toyota’s other pet project in battery technology, LiO2, could be commercially available around 2025. LiO2 batteries interact with the oxygen in the air and are perhaps four or five times as energy-dense as Li-ion. Energy density is slowly approaching that of gasoline, which means that electric vehicle range, when powered by solid state or LiO2, could rival conventional vehicles for range as well as upfront costs.