The value of pre-test CT scanning for battery lifetime testing
Why pre-test CT scanning for cell evaluation?
Whether you’re making batteries, buying batteries, or both, lifetime testing is likely the slowest part of your product development cycle. Cycle life and calendar life experiments can take weeks, months, or even years to ensure that your cells can meet your performance requirements and warranty specifications. While approaches such as accelerated testing (e.g., high temperature testing) and data-driven battery lifetime prediction can help shorten these iteration cycles, most battery testing labs are inevitably bottlenecked by lifetime testing.
Beyond accelerated testing and lifetime prediction, there’s a third approach that we believe is underappreciated today: pre-test inspection. In other words, taking a quick, high-resolution look inside your cells via CT scanning before they cycle for months or years is almost always a worthwhile investment. Here's why:
Test the correct batch: Pre-test inspection can provide confirmation that you’re testing the cells that you think you are testing. Given the rise of counterfeit batteries and the simple possibility of shipping & handling mistakes, pre-test inspection offers peace of mind that your cell testing is proceeding as planned.
Deconvolute defect-driven signal from true electrochemical signal: Pre-test CT scanning can identify cells with latent defects. As we’ve discussed in our article on battery quality, latent defects do not initially have an electrochemical signature. However, over time, these defects can lead to battery failure. Removing cells with latent defects (unless they are of specific interest) will deconvolute the cell’s electrochemical behavior from that introduced by defects—and ensure that the cells you are interested in run to completion.
Quantify your cells’ build variability: As Dechent et al. discuss, cell-to-cell variability impacts the recommended number of cells to test per condition. Pre-test inspection can quantify cell-to-cell variability. Without this information, your cell testing may be inefficient (i.e., testing too many cells per condition) or, worse, provide insufficient statistical power to draw conclusions from your data.
Find and leverage limit samples: Pre-test inspection can enable test plan creation to study “worst-case” cell behavior. As the industry pushes to improve energy density and fast charging capability, some aggressive lab tests might pose a safety risk. This risk that will be exacerbated in certain cells, such as a cell with low n:p ratio tested with an aggressive fast charge profile (which is a lithium plating risk). Pre-test CT can enable both quantification and selection of these “worst-case” cells.
Prevent safety events in the lab: A cell that unexpectedly goes into thermal runaway can cause a lab shutdown or, worse, human harm. Pre-test inspection can help you steer clear of safety events, especially when using accelerated testing.
Interpret unexpected electrochemical results: Pre-test CT can help diagnose anomalous behavior observed in lifetime testing. When these events occur, pre-test data will enable analysts to draw the correct interpretations and conclusions — in short, if this issue has product-level implications or is an artifact of the cell or test.
Unlock new insights: Pre-test inspection can unlock additional levels of insight into cell behavior over life by comparing during-test or post-test inspection results (which we also recommend 🙂). Today, many battery engineers add periodic reference performance tests (RPTs) to their cycling/storage tests to obtain standardized measurements of capacity, energy and rate capability over life. Adding additional inspection techniques such as CT scanning to these periodic checks allows for a rich, multidimensional understanding into battery behavior.
In short, pre-test CT scanning almost always provides more value than it costs and enables faster, more informed decisions around changes to cell materials, design, and use.
Pre-test CT in practice
Depending on your needs, you may want to add pre-test CT scanning for every cell that you put on test—or just a sample of cells from every batch. For instance, a cell qualification lab working with a pilot line developing a new battery chemistry will probably want to inspect a higher fraction of cells than a consumer electronics OEM sourcing cells from top-tier suppliers.
The importance of pre-test inspection is most pronounced when using electrochemical cycling/storage data for data-driven battery lifetime prediction using ML/AI. Battery engineers often develop these models to compare how different cell types or cycling profiles will perform, but the success of these models is dependent on collecting clean data that captures the intended signal—and not the noise. If some cells in your training or inference sets are convoluted by electrochemically-significant defects and/or high build variability, the model may produce inaccurate or imprecise predictions and thus produce incorrect conclusions.
How can I access low-cost, high-resolution, high-throughput cell CT scanning?
If these conclusions resonate with you, consider Glimpse for your battery CT needs. Glimpse offers two products. The first (“Scan on Demand”) is very simple: Send your cells to us in Boston and we’ll scan them quickly and at an extremely competitive price. We'll host the data on the Glimpse Portal™ and then send your cells back. This model is most suitable for smaller customers who don’t need a scanner on-site. The second model is On-Premise Scanning, where we deploy a tailored hardware and software solution to meet your battery inspection needs. If we might be able to help you, let us know here!
