a) Experimental setup showing rotation stage and in-built electrical slip ring connection. b) Stitched reconstruction of a full commercial Duracell CR2 battery showing the casing (orange), current collector mesh connected via a tab to the terminal (green), and MnO2 electrode (gray). The black square represents the region which was scanned during continuous X-ray CT. c) Reconstructed tomogram of the section captured during continuous X-ray CT with orthoslices in the X, YZ, and XZ planes. d) Isolated XY slice showing battery casing and current collecting mesh (white) and MnO2 electrode (gray). e) Isolated XZ slice. (Image Credit: University College London)
Paul Shearing: We want to understand as much as we possibly can about degradation and ultimately failure of these cells, so that we can begin to understand what safety devices can either prevent those failures from occurring, or worstcase scenario: how we can mitigate against the worst possible effects of those failure events. That could be the shutting down of a single cell level, or preventing the propagation of failure from one cell to another if we’re looking at much larger packs.

In the rare event when they do fail in response to these very demanding applications — whether that’s because of high-rate discharge or high pressure, low pressure, or higher temperatures — we want to understand how these failure events happen so we can design next-generation batteries where we can mitigate against these failures.

P&IT: What is most exciting about this kind of technology?

Paul Shearing: This is completely new. Only relatively recently have people been able to image using video cameras at tens of thousands of frames per second. All of a sudden, now we can image using Xrays at tens of thousands of frames a second. This is a really exciting and enabling technology. The limits are your imagination in terms of what you want to look at. You’re now slowing down time into this wonderful capability to be able to see subsurface.

There’s a huge challenge in understanding not just the changes in cell architecture but also the change in electric microstructure, the changes in the electrochemistry, the changes in the materials chemistry. It’s a very, very rich problem to be able to tackle using a range of imaging and spectroscopy tools, and one that we expect to keep us busy for some years to come.

For more information about UCL’s 3D imaging and battery testing efforts, visit https://www.ucl.ac.uk/electrochemicalinnovation-lab/research/imagingdiagnostics/battery_safety .

Photonics & Imaging Technology Magazine

This article first appeared in the May, 2016 issue of Photonics & Imaging Technology Magazine.

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