The Electrochemical Society hosted Peter Attia’s live webinar, “Enabling battery quality at scale,” on September 18, 2024. A live Question and Answer session followed. Dr. Attia’s answers to questions not addressed during the broadcast follow.
NOTE: Registration is required to view the webinar replay.
Q&A
What defect rates are needed to avoid battery pack failure?
The short answer is that it depends on lots of factors such as the magnitude of the failure, pack architecture, BMS system, etc. However, in some cases, even a single defective cell can cause the entire pack to fail. A simple example is an open-circuit failure in a battery pack consisting of cells in series; just like old-school Christmas tree lights, the entire string of cells will fail if only one cell has open-circuit failure.
How can AI help with inspecting battery quality?
Lots of ways! First, AI-based techniques can be used to improve scan time and/or image quality. Second, AI can be used to detect defects in CT images. Last, AI can be used to identify correlations between CT data and production data to root cause quality issues.
Which battery form factors are best suited for CT scanning?
Generally, the smaller the cell, the higher the resolution that we can obtain. Cylindrical cell scans tend to yield the best results both because they’re typically smaller than pouch and prismatic cells and because their geometry is best suited for CT scanning. However, we routinely scan cylindrical, pouch, and prismatic cells for our customers today.
How can CT scanning be complementary to electrochemical testing?
CT scanning and electrochemical testing are highly complementary. Perhaps the most common use case is to CT scan cells periodically over the course of a cycle life test or as a function of SOC. Electrochemical testing can also be used to measure cell energy, which can correlate with cell dimensions. Finally, electrochemical testing and CT scanning can be used complementarily to catch more defects and quality issues. We will publish some work on this in ECS journals soon!
How can high-throughput inspection be used for battery second-life applications?
In principle, we can scan cells disassembled from a battery pack and determine if the cell is suitable for a second-life application or should be recycled. In some cases, we may only need to scan a few cells from a pack to make this determination.
Is there a potential safety role for high-speed x-ray spectroscopy to monitor, for example, electrolyte composition?
I’m not aware of high-speed x-ray spectroscopic techniques capable of penetrating commercially sized cells, but this technology sounds very interesting!
Is there a way to identify the cell ID number on this Glimpse user interface so that you can identify which cell could be damaged or has detect? Do you use any barcoding to input your cell location spatially?
Yes, please visit https://app.glimp.se to see how cell barcodes are present in our interface. We use a barcode scanner to read cell barcodes in our own lab today. For customers using our technology in production environments, we work together to ensure cell handling and barcode reading is smooth.
Is there any relationship between irreversible SoC to a full charge SoC percent ratio for indicating the cell life or cell health condition?
Yes, the irreversible swelling in a cell often correlates with the irreversible capacity loss in the cell.
What type of cell and what chemistry do you see as most reliable?
It’s a bit too early to say since we haven’t scanned enough cells yet. Some defects will occur on a “per-cell” basis (e.g., issues with tabs and terminals), in which case larger form factors like prismatic will be best. Still other defects will occur on a “per-energy basis” (e.g., electrode coating issues), in which case smaller form factors like cylindrical may be more reliable.
What about quantum battery? CT, can be used for future?
While I’m not aware of the specifics of this “quantum battery” design, we have already scanned all sorts of interesting chemistries: LFP, NMC, lithium-metal, sodium-ion, sodium-metal, and more. In general, we can obtain high-quality images as long as the anode and cathode have different elemental compositions—which is almost true by definition in a battery!
What percentage of cell failure has been detected by x-ray CT scans?
While it’s difficult to quantify an exact percentage, x-ray CT can quickly detect many defects that no other technique can catch. Some of these defects include electrode overhang violations, electrode buckling and wrinkling, metallic particle contamination, and many more.
Would spectral photon counting technique help on scan speed?
Photon-counting detectors are indeed an exciting next-generation detector technology that we’re investigating!
Is there a specialized CT scanner needed for this?
No, we can improve the scan time and image quality for any CT scanner. The scanner in our own lab today is “off-the-shelf” but with components specifically selected for the high-throughput battery inspection use case. We are continuously upgrading our image processing pipeline to increase scanning throughput. In parallel, we are co-developing a next-generation scanner with our hardware partners that will reduce the scan time to seconds per (cylindrical) cell.
You mentioned a scan time of two minutes per cell but note the analysis time per cell? In other words, what is the overall total inspection time per cell at current levels of performance?
With the Glimpse Portal, the analysis time is seconds per cell, especially when using our automated inspection dashboards. That said, some customers spend many hours reviewing their scan images to fully understand the quality of the construction of their batteries. You can check it for yourself at https://app.glimp.se.
Can acoustic techniques provide comparable insights; what’s limiting the resolution levels?
The resolution of a characterization technique is fundamentally linked to the wavelength of the probing radiation, particles, or acoustic waves used in the technique. However, acoustic waves typically have wavelengths of ~0.5–1mm. Many battery defects occur on the electrode level, for which <50µm resolution is typically required. That said, acoustic characterization of batteries is especially useful for probing electrolyte wetting, and the capital equipment cost is often lower than CT.
Can you comment on radiation risk to operator?
The radiation dose for an operator is minimal. CT integrators must confirm that their systems emit very low doses of radiation; they typically do this by shielding the system in a thick lead container (lead absorbs a lot of x-rays). The yearly radiation exposure of a full-time CT operator is, at worst, around one third of the dose from a single chest CT scan.
We thank our webinar sponsor who made this complimentary program possible!
