Abstract
This method for virtually unrolling the jelly roll of a lithium ion cell using X-ray CT highlights the predictability of macro deformations formed while cycling. The failure is shown to propagate from nucleation points present since production.
Highlights
Lithium-ion batteries have become ubiquitous in modern life due to their high energy and power densities, relatively long cycle life and portability
X-ray computed tomography (CT) was used to image and examine an 18650 Li-ion cell as it aged and its capacity faded beyond primary use
The location of the eventual failure and delamination in the electrode was near an obvious imperfection in the jelly-roll that was visible before the battery was cycled
Summary
Lithium-ion batteries have become ubiquitous in modern life due to their high energy and power densities, relatively long cycle life and portability. This widespread deployment has generated a huge market and increased the need for improved performance, longevity and reliability of cells. X-ray CT has been shown to be a powerful, non-destructive technique to investigate batteries with studies highlighting its efficacy in identifying microstructural evolution[9,10] and cell failure.[11,12]. Virtual unrolling of the jelly-roll structure provides a radially resolved deformation map of a battery electrode revealing, for the rst time, that initial defects in the jelly-roll are nucleation points for electrode deformation which can be correlated to ageing and cell failure. The rapid nature of the X-ray CT scans, coupled with fast analysis, provides a pathway to an in-line quality assurance process, which currently rely on optical assessments[15] of the electrodes prior to assembly, which could have a signi cant impact on safety, durability and recyclability of Li-ion batteries
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