Toyota has achieved a ‘breakthrough’ in battery technology which enhances the battery life and hence driving range. Toyota Motor Corporation through a press release announced that it has developed a method for observing the behavior of lithium ions (Li-ions) in an electrolyte when a Li-ion battery charges and discharges and by using this method, it is possible to observe in real-time, the deviation of Li-ions one of the causes of deterioration in the performance of Li-ion batteries. Toyota believes that this will provide essential guidelines for R&D that aims to improve the performance and durability of batteries, which would lead to longer battery life, as well as longer driving ranges for plug-in hybrid vehicles (PHVs) and electric vehicles (EVs).
The Li-ions play an essential role within the electrolyte during battery charging and discharging.It has been known that Li-ion deviation occurs in the electrodes and electrolyte as a result of charging and discharging, and such deviation has been believed to limit the usage area of batteries, which is one factor that reduces the area in which the maximum performance of the battery can be achieved. When investigating the mechanism of Li-ion deviation, however, confirming the behavior of Li-ions in the electrolyte under the same environment and conditions as when it is being used in related products was not possible using existing methods.
In place of the electrolyte with phosphorous that is used in many Li-ion batteries, a new electrolyte with heavy elements is being utilized instead, thus replacing the phosphorous-containing ions that the Li-ions bind to as they move in the electrolyte with heavy element-containing ions. Heavy elements transmit less of the X-rays than phosphorous, and the shadows on the images taken after the X-rays pass through are darker. By observing the behavior of the heavy elements, it is possible to observe the deviation behavior of the Li-ions which are bound to them in the electrolyte.
By using the method described above, and a battery that is similar to that of related products such as laminated cell under the environment and conditions that resemble those of actual battery use, it is possible to observe in real-time, the process of Li-ion deviation that occurs in electrolytes during the course of battery charging and discharging. This observational method was jointly developed by Toyota Central R&D Labs, Inc., Nippon Soken, Inc., and four universities.
Going forward, Toyota will observe the behavior of Li-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 to improve the performance and durability of batteries, to bring about longer battery life and longer driving ranges.