Image courtesy of NYU's Jerschow lab

It is now possible to peer inside batteries, in real time, to study how their power is degrading.

A team of chemists from New York University has developed a way to yield highly detailed, three-dimensional images of the insides of batteries using a technique based on magnetic resonance imaging (MRI).


As well as learning more about why batteries lose power and performance over time, the findings could help develop the next-generation technology desperately needed to power future phones and wearables.

The work, described in the Proceedings of the National Academy of Sciences journal, focuses on rechargeable Lithium-ion (Li-ion) batteries. These batteries are used in phones, electric cars, laptops, and most other electronics.

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Many see lithium metal as a promising, highly efficient electrode material, which could boost performance and reduce battery weight. However, during recharging, it builds up deposits – or "dendrites" – that cause performance loss and safety concerns, including fires and explosions.

As a result, monitoring the growth of dendrites is crucial to producing high-performance batteries with this material.


Modelo

Click the image above to explore a 3D, interactive model of a battery with dendrites

"One particular challenge we wanted to solve was to make the measurements 3D and sufficiently fast, so that they could be done during the battery-charging cycle," explained NYU Chemistry Professor Alexej Jerschow.

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"This was made possible by using intrinsic amplification processes, which allow one to measure small features within the cell to diagnose common battery failure mechanisms. We believe these methods could become important techniques for the development of better batteries."

Current methods for doing so, developed previously by the same team, used MRI technology to look at lithium dendrites directly. However, this technique resulted in lower sensitivity and limited resolution images, making it difficult to see dendrites in 3D and to understand the conditions under which they build up.

With this in mind, the researchers concentrated on the lithium's surrounding electrolytes – substances used to move charges between the electrodes. Specifically, they found that MRI images of the electrolyte became strongly distorted near dendrites, offering a highly sensitive way to measure when and where they grow.


What's more, by capturing these distortions, the scientists could construct a 3D image of the dendrites. Alternative methods require the batteries to be opened up which ultimately destroys the dendrite structure and changes the chemistry of the cell.

"The method examines the space and materials around dendrites, rather than the dendrites themselves," added Andrew Ilott, an NYU postdoctoral fellow and the paper's lead author.

"As a result, the method is more universal. Moreover, we can examine structures formed by other metals, such as, for example, sodium or magnesium–materials that are currently considered as alternatives to lithium. The 3D images give us particular insights into the morphology and extent of the dendrites that can grow under different battery operating conditions."