Toyota Research Aims for Longer-Range EV Battery

Toyota is claiming a world first in extending the potential range and service life of batteries used in hybrid and electric vehicles.

A new battery-monitoring system can recover much of the energy lost during the charging and discharging process in lithium-ion batteries, the automaker says.

The system observes how lithium ions behave in an electrolyte in batteries used in vehicles such as the Toyota Prius+ and Prius Plug-in Hybrid, both when the battery is being charged and discharging power. It allows real-time observation of the deviation of lithium ions – one of the causes of deterioration in battery performance.

Toyota believes the data can be the basis for forming guidelines to help in the research and development of batteries with improved performance and durability, leading to longer battery life and driving ranges for PHEVs and EVs.

It has been known that lithium-ion deviation occurs in the electrodes and electrolyte as a result of charging and discharging and is believed to restrict the usage area of batteries, reducing their maximum performance.

The system can observe deviation by the beamline in Toyota’s Super Photon ring-8 synchrotron radiation facility. The automaker says the facility generates the world’s highest-performance synchrotron radiation, produces high-intensity X-rays about 1 billion times more powerful than those generated by X-ray equipment. This makes it possible to create 0.65 micron/pixel high-resolution and 100-ms/frame high-speed measurements.

The system also replaces the electrolyte with phosphorous used in many Li-ion batteries with a new electrolyte with heavy elements, replacing the phosphorous-containing ions to which the lithium ions bind as they move in the electrolyte with heavy-element-containing ions. Heavy elements transmit fewer of the X-rays than phosphorous and the shadows on the images taken after the X-rays pass through are darker. By observing the heavy elements’ behavior, it is possible to observe the deviation behavior of the li-ions that are bound to them in the electrolyte.

This observational technique was jointly developed by Toyota Central R&D Labs, Nippon Soken and four Japanese universities.

Toyota now will observe the behavior of lithium ions caused by differences in the materials and structures of cathodes, anodes, separators and electrolytes, as well as the differences in battery control. Analyzing the mechanisms that cause deterioration of battery performance will lead to R&D that can help improve battery efficiency and durability, extending both battery life and driving range.

A Toyota U.K. spokesman tells WardsAuto, “This is an ongoing experiment and, as such, Toyota would not release figures on how much more performance and longevity the observation system can harvest from the batteries until it has some definitive data to draw on.”