Scan your battery with MRI: Charging up an insider view

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  • Published: Apr 1, 2012
  • Author: David Bradley
  • Channels: MRI Spectroscopy
thumbnail image: Scan your battery with MRI: Charging up an insider view

All charged up

See through battery.

A UK-US collaboration has exploited the power of magnetic resonance imaging to take a diagnostic look at one of the perennial problems of modern technology: the chemistry of rechargeable batteries.

Anyone who has owned a portable electronic gadget during the last decade or so will have relied on the almost ubiquitous lithium-ion battery. They precluded the need to use noxious cadmium and purportedly side-step the memory charge problem of so-called Ni-cad batteries. But, they are far from perfect, they rarely last as long in use as the manufacturers of said gadgets often claim and they do wear out, usually within about 18 months of purchase and usually on the day when their use is most likely to be most problematic for the user. Moore's Law may apply to silicon chips, but Sod's Law is the more common legal mandate of lithium batteries.

As such, there is much room for improvement in terms of reducing charging times, extending discharge times and increasing the lifespan of the battery by boosting the number of times it can be charged and discharged. There is also an urgent need to increasing the electrical power that might be harvested from a single charge for more demanding applications such as powering motors, whether in low-local-polluting vehicles, machinery or other equipment and not just for smart phones, tablet PCs and portable media players and digital cameras.

Room for improvement

Improvements could be made if scientists could see inside batteries before use, in use and at end of life without destroying them in the process. Now, a team led by Clare Grey from Cambridge University and Alexej Jerschow from Stony Brook University, and New York University have turned to lithium-7 magnetic resonance imaging (MRI) to allow them to image the internals of a battery in a non-invasive manner and to focus on the microstructural lithium within. Writing in the journal Nature Materials, the team suggests that their approach could become a useful diagnostic tool in the development of improved battery performance and safety.

MRI, of course, is most commonly used in medicine, but engineers and materials scientists have turned to this powerful technique with great success. Usually, it works best if there is not a large quantity of metal present in the object being imaged, whether living being or engineering component. Unfortunately, as the name would suggest, there is rather a lot of metal in a lithium battery.

The collaborators have turned this limitation on its head. Given that the radio frequency electromagnetic field essential for MRI does not penetrate metal, they can in fact perform rather sensitive measurements on the surface of a conductor. To examine a lithium-ion battery, for example, the team could visualize directly the build-up of lithium metal deposits on the electrodes after the battery has been charged. These unwanted deposits are notorious for causing battery failure, overheating and, in extreme cases that have been well publicised by the media, can cause the battery to combust or even explode.

MRI allows the team to look at how such lithium deposits might change and practically be reduced by changes in the configuration of the battery's electrodes and internal structure. In principle, MRI could be used to test many different battery designs and materials under normal operating conditions.

Internal insights

"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," explains Jerschow. "Both electrolyte and electrode surfaces can be visualized with this technique, thus providing a comprehensive picture of the batteries' performance-limiting processes."

Grey adds that MRI is an exciting technique to use because it allows the team to see precisely where different chemical species within the battery reside without having to dismantle the battery. "The work clearly shows how we can use the method to identify where lithium deposits form on metal electrodes," she says. "The resolution is not yet where we want it to be and we would like to extend the method to much larger batteries, but the information that we were able to get from these measurements is unprecedented."

"The team, which includes Srinivasan Chandrashekar, Nicole Trease, and Hee-Jung Chan, also envisions that one could study irregularities and cracks on conducting surfaces in the materials sciences field," Jerschow told SpectroscopyNOW, "The methods developed here will be highly valuable in the quest for enhanced battery performance and in the evaluation of other electrochemical devices, such as fuel cells."

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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