Toyota has developed a new method for observing the behavior of lithium ions in an electrolyte during battery charging and discharging, making it possible to observe in real time the deviation of ions, which is one of the causes of deterioration in the performance of Li-ion batteries.

It is already known that lithium ion deviation occurs both in electrodes and electrolyte as a result of charging and discharging, and such deviation is believed to reduce the area in which the maximum performance of a battery can be achieved. However, confirming the behavior of ions in the electrolyte under actual use conditions was not possible using previous methods.

Toyota scientists used an apparatus called Beamline2, which generates X-rays a billion times more powerful than those of a medical X-ray machine. This makes it possible to create video images with a resolution of 0.65 micron/pixel and 100 ms/frame. The researchers replaced the usual phosphorous in the electrolyte with heavy elements, which transmit less of the X-rays, yielding a sharper image. By observing the behavior of the heavy elements, the researchers were able to observe the deviation behavior of the lithium ions which are bound to them in the electrolyte.

Toyota now plans to observe the behavior of ions in batteries with different cathodes, anodes, separators, and electrolytes, as well as differences in battery control. Analyzing the mechanisms that cause deterioration of battery performance should lead to insights that can improve battery life and vehicle range.

Condition While Discharging

Newly-Developed Observation Method

Li-ion Deviation in Electrolyte During Battery Discharge

Source: Toyota