Tohoku Univ Takes MRI Images of Li-ion Battery

Jul 9, 2009 16:53 Yukiko Kanou, Nikkei Electronics

A Japanese research group announced that it has succeeded in taking cross-sectional images of a Li-ion secondary battery for the first time in the world by using MRI (magnetic resonance imaging).

The research group was led by Jyunichi Kawamura and Yoshiki Iwai, professors of the Institute of Multidisciplinary Research for Advanced Materials at Tohoku University. This study was conducted as part of a research contracted by the New Energy and Industrial Technology Organization (NEDO).

To create images, MRI emits electric waves to an object in a strong magnetic field and detects weak electric waves reflected by the spin of atomic nuclei. However, electric waves do not pass through Li-ion secondary batteries because they have a metallic chassis and contain a large amount of metal inside. Therefore, it has been regarded as difficult to use MRI to take images of the inside of a Li-ion secondary battery.

This time, the research group succeeded in taking the MRI images by using glass and plastic for the chassis, rearranging the electrodes and making other improvements to the Li-ion secondary battery.

Specifically, it took MRI images of not only hydrogen nuclei (protons) but also Li ions themselves, which are said to be very difficult to detect because of their low sensitivity. The images of protons have a pixel count of 65,000 and a resolution of 16μm, and those of Li ions have a pixel count of 16,000 and a resolution of 32μm.

With the new method developed by the group, it is possible to observe the distribution of Li ions inside a Li-ion secondary battery and such phenomena as generation of gas and decomposition of battery electrolyte when the battery is repeatedly charged and discharged. As a result, it will help understand how heat generation and ignition occur when a battery is mishandled, and develop technologies to improve safety and prevent degradation of a battery.

For the future, the research group aims to observe the movement of Li ions inside a Li-ion secondary battery and the degradation of battery electrolyte in three-dimensional movies.

The group will announce the results of the study at a debriefing session held by NEDO at Tokyo International Exchange Center July 10, 2009.

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