Cell defects - Glimpse

Using CT Scanning to Detect Battery Defects

Author: Glimpse

Battery defects are a major scourge on the industry. In fact, battery defects have been deemed responsible for major billion-dollar electric vehicle recalls.1 Furthermore, dozens of battery safety incidents have been attributed to poor-quality and/or counterfeit batteries, which often have poor performance, reliability, and safety.2–6 In short, battery defects directly threaten both the financial success of cell makers and cell buyers and, more importantly, human life.

Historically, efficient evaluation of battery quality has been a challenge. Previous works studying battery quality primarily resort to visual inspection and simple electrochemical measurements (which provide limited insight) and/or cell teardowns (which are slow, expensive, and sometimes dangerous).2–4 A few studies have used computed tomography (CT) scanning, the same technology as CAT scans, to study the internal structure of suspected low-quality batteries.2–5 However, this technique remains underutilized for battery quality control to its (historically) long acquisition times and long analysis times.

To study this issue further, Glimpse identified nine types of 18650 batteries sold on Amazon.com and purchased a few batteries of each type:

a number of cells lined up for analysis
Figure 1. Images of the nine battery types investigated in this study. 

Each of these cells was scanned using Glimpse’s high-quality, 2-minute CT scanning recipe. The CT scans revealed that some of the cells appeared to have high quality:

Cell defects - Glimpse
Figure 2. CT scan images of high-quality cells.

However, many of the cells had critical defects, or defects that will very likely lead to internal shorting and/or a safety event:

Cell defects - Glimpse
Figure 3. CT scan images of critical cell defects and their potential impact.

Other cells had “marginal” defects, or defects that may or may not have electrochemical impact. The impact of these defects will depend on the aggressiveness of the use case, although many of these issues could very well cause internal shorting and/or a safety event:

Cell defects - Glimpse
Figure 4. CT scan images of marginal cell defects.

Lastly, some cells had “design defects”, or poor design characteristics that threaten cell safety and reliability. Some examples include missing cell safety devices and very large cores (which have low cell energy and also are a buckling risk):

Cell defects - Glimpse
Figure 5. CT scan images of design defects.

Note that CT scanning can be used to detect quality issues in pouch and prismatic cells as well:

Cell defects - Glimpse
Figure 6. CT scan images of a prismatic cell. The “waviness” of the electrode layers could lead to lithium plating and/or internal shorting.

Overall, these results clearly indicate that low-quality batteries are widespread and that CT scanning is an effective way to detect them.

Glimpse is a Boston-based startup pioneering high-throughput CT scanning for battery quality control by solving CT scanning’s two major bottlenecks: scan time and analysis time. First, most high-quality battery CT scans today take an hour or two, which is much too slow for battery quality control. Glimpse has reduced scan time to two minutes using a combination of hardware and software innovations, unlocking industry-leading throughput and image quality. Second, CT scanners produce massive quantities of data; each high-resolution CT scan can be dozens of gigabytes each, which makes data analysis slow and labor-intensive. To reduce the analysis time of CT scanning, Glimpse has developed a cutting-edge compute, computer vision, and visualization platform that we call the “Glimpse Portal” (see our free demo here). The Glimpse Portal allows battery engineers to understand the quality of their batteries in seconds instead of hours. To learn more, visit https://glimp.se or contact us here.

References

  1. Global Safety Field Investigations. DCS5937: Chevrolet Bolt Battery Safety Recall Update. https://static.nhtsa.gov/odi/rcl/2021/RCMN-21V650-0383.pdf (2021).
  2. Saxena, S., Kong, L. & Pecht, M. G. Exploding E-Cigarettes: A Battery Safety Issue. IEEE Access 6, 21442–21466 (2018).
  3. Kong, L., Das, D. & Pecht, M. G. The Distribution and Detection Issues of Counterfeit Lithium-Ion Batteries. Energies 15, 3798 (2022).
  4. Joshi, T., Azam, S., Juarez-Robles, D. & Jeevarajan, J. A. Safety and Quality Issues of Counterfeit Lithium-Ion Cells. ACS Energy Lett. 8, 2831–2839 (2023).
  5. Wu, Y. et al. Analysis of Manufacturing-Induced Defects and Structural Deformations in Lithium-Ion Batteries Using Computed Tomography. Energies 11, 925 (2018).
  6. Attia, P. M., Moch, E. & Herring, P. K. Perspective: Challenges and opportunities for high-quality battery production at scale. Preprint at https://doi.org/10.48550/arXiv.2403.01065 (2024).

See also: Computed Tomography Scanning of Battery Cells, Quality, Manufacturing

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