Magnetic resonance imaging shows batteries' inner workings

The technique, described in Nature Materials and developed by researchers at Cambridge University, Stony Brook University and New York University, also creates the possibility of improving battery performance and safety by serving as a diagnostic of its internal workings.

According to a statement, MRI has been successful in the medical field for visualising disorders and assessing the body’s response to therapy. However, MRI is not typically used in the presence of a lot of metal — a primary component in many batteries. This is because conducting surfaces block the radio-frequency fields that are used in MRI to see beneath surfaces or inside the human body.

The researchers are said to have turned this limitation into a virtue. Because radio-frequency fields do not penetrate metals, it is possible to perform very sensitive measurements on the surfaces of the conductors. In the case of lithium-ion batteries, for example, the team was able to directly visualise the build-up of lithium metal deposits on the electrodes after charging the battery. Such deposits can also detach from the surface, eventually leading to overheating, battery failure, and — in some cases — to fire or explosion.

Visualising small changes on the surface of the batteries’ electrodes allows, in principle, for the testing of many different battery designs and materials under normal operating conditions.

The work is the result of a collaboration between Clare Grey, associate director of the Northeastern Center for Chemical Energy Storage and a professor at Cambridge and Stony Brook universities, and Alexej Jerschow, a professor in the Department of Chemistry at New York University who heads a multi-disciplinary MRI research laboratory.

‘New electrode and electrolyte materials are constantly being developed and this non-invasive MRI technology could provide insights into the microscopic processes inside batteries, which hold the key to eventually making batteries lighter, safer, and more versatile,’ said Jerschow. ‘Both electrolyte and electrode surfaces can be visualised with this technique, thus providing a comprehensive picture of the batteries’ performance-limiting processes.’