Toyota has found a pathway to adopt lithium-ion battery technology and join the plug-in electrified vehicle race.
Toyota said that its soon-to-be-launched Prius Prime plug-in hybrid electric vehicle will use lithium-ion batteries with enough energy to transport the car about 60 kilometers (37.3 miles) on battery alone before the gasoline engine takes over. The Prius Prime’s range is expected to be listed in the U.S. at around 25 miles (40.2 km) per charge on battery alone.
Toyota Motor Corp. had taken a more conservative approach than rivals such as Tesla, Nissan, and General Motors, which led the first launches of PEVs. Toyota has had concern over the cost, size, and safety for the battery packs needed in a PEV that have typically used a chemical combination of nickel, cobalt and manganese. Much of that concern has come from the potential safety hazards, including having the battery pack overheat and catch fire if not properly designed, manufactured, and controlled – something that competitors have experienced.
Toyota said that its confidence in its battery’s safety and stability comes from improved control technology that precisely monitors the temperature and condition of each of the 95 cells in its new battery pack. Toyota has worked with Panasonic Corp., which also produces Li-ion batteries with Tesla, to improve the precision in battery cell assembly with some fine tuning. The introduction of even microscopic metal particles or other impurities can trigger a short-circuit, overheating, and potential explosion, Toyota said.
“Our control system can identify even slight signs of a potential short-circuit in individual cells, and will either prevent it from spreading or shut down the entire battery,” said Hiroaki Takeuchi, a senior Toyota engineer involved in the Li-ion technology.
“We have double braced and triple braced our battery pack to make sure they’re fail-safe … It’s all about safety, safety, safety,” Takeuchi told Reuters.
Toyota has mainly used the more mature nickel-metal hydride batteries in the conventional Prius hybrid. The Japanese automaker did use Li-ion batteries starting in 2012 with the first plug-in hybrid Prius. The Prius Plug-in Hybrid had been put on hold and became the soon-to-be-released Prius Prime plug-in hybrid using the new Li-ion battery pack.
In May 2014, Tesla Motors said that its deal to supply its battery packs and motors to Toyota would conclude that year. Toyota had taken a 2.4 percent stake in Tesla’s startup in 2011, and had made a May 2012 agreement that it would buy Tesla components for 2,600 electric Toyota RAV4 EVs over three years. Toyota would be ending the RAV4 EV model in 2014, according to a Tesla quarterly filing reported by Bloomberg.
Toyota seemed to have left PEVs behind, focusing instead on hybrids and hydrogen fuel-cell vehicles. Finding its own pathway for Li-ion batteries gives the automaker more choices for bringing PEVs to market.
The new battery packs designed by Toyota and Panasonic have shrunk the size of each cell. That’s closed the distance between the anode and cathode, where active ions travel when charging and discharging.
Toyota said that going this route has doubled battery capacity to around 8.8 kilowatt hours, while only increasing the battery pack size by around two-thirds and its weight by a half. The cost of the battery is also falling.
Toyota appears to be influenced by governments in the U.S. and China encouraging automakers to make more all-electric vehicles. Toyota has said that it does make sense to have a range of batteries that can deliver hybrids, plug-in hybrid, and all-electric vehicles to global markets.