Toyota Says Lithium Ion Batteries Now Safe To Use

Until now, Toyota has been cool to the idea of using lithium ion batteries. Instead, it has preferred nickel metal hydride batteries in its hybrid cars. The problem, Toyota says, is that traditional lithium ion batteries can explode or burst into flame. That’s what is happening with the batteries in the new Samsung Galaxy 7 smartphones. Until recently, Toyota has been content to develop hydrogen fuel cell technology for its zero emissions cars of the future.

Now Toyota says it will use a lithium ion battery developed in cooperation with Panasonic in its new Prius Prime plug-in hybrid. “It’s a tall order to develop a lithium ion car battery which can perform reliably and safely for 10 years, or over hundreds of thousands of kilometers,” said Koji Toyoshima, the chief engineer for the Prius. “We have double braced and triple braced our battery pack to make sure they’re fail-safe … It’s all about safety, safety, safety,” he says. The Prius Prime will have an 8.8 kWh lithium ion battery, which should give the driver more than 30 miles of all electric range before the onboard gasoline engine kicks in.

Vastly improved control technology is what gives Toyota the confidence to use lithium ion batteries in the Prius Prime. The new system precisely monitors the temperature and condition of each of the 95 cells in its new battery pack. “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.

Panasonic has used its expertise in manufacturing lithium ion cells to increase the precision of battery cell assembly. Even microscopic metal particles or other impurities can trigger a short-circuit, overheating and potential explosion. “The environment where our lithium ion batteries are produced is not quite like the clean rooms where semiconductors are made, but very close,” Takeuchi said.

Battery experts say increasingly sophisticated systems that can track individual cell conditions are becoming closely guarded trade secrets. “State of charge management, safety management, and algorithm development is becoming one of the higher tiers of proprietary internal development,” said Eric Rask, principal research engineer at Argonne National Laboratory. “It’s very internal, very strategic, and companies are seeing management algorithms as a competitive advantage.”

“Developing lithium-ion batteries for both hybrids and plug-ins will enable us to also produce all-electric cars in the future,” said Toyoshima said. “It makes sense to have a range of batteries to suit different powertrains.” The use of the word “will” is important. It marks a possible turning point for Toyota, which needs to compete with battery electric cars coming from most of the world’s major manufacturers.

With hydrogen refueling infrastructure virtually non-existent in most of the world, fuel cell cars are not going to be competitive any time soon.  Hyundai will introduced a battery powered Ioniq in 2017. Toyota can’t afford to get too far behind in the zero emissions market segment.

Source: Reuters  Photo credit: Toyota