Lithium-ion Battery Electrode Inspection Using Flash Thermography
This thermal image was recorded using a new tool developed at Purdue that detects flaws in lithium-ion batteries as they are being manufactured, a step toward reducing defects and inconsistencies in the thickness of electrodes that affect battery life and reliability. (Purdue University image)
By: Nathan Sharp, Douglas Adams, James Caruthers, Peter O’Regan, Anand David, Mark Suchomel
WEST LAFAYETTE IN, USA. ??? Researchers at Purdue University have created a new tool to detect flaws in lithium-ion batteries as they are being manufactured, a step toward reducing defects and inconsistencies in the thickness of electrodes that affect battery life and reliability.
The electrodes, called anodes and cathodes, are the building blocks of powerful battery arrays like those used in electric and hybrid vehicles. They are copper on one side and coated with a black compound to store lithium on the other. Lithium ions travel from the anode to the cathode while the battery is being charged and in the reverse direction when discharging energy.
Nonuniformity in lithium-ion battery electrode thickness or composition can lead to reduced performance and longevity. Currently battery manufacturers have no way to quickly and accurately assess electrode quality during the manufacturing process. A finite element heat transfer model based on heat conduction equations has been developed to provide theoretical justification and insight. The model shows that a heat pulse to the back of a current collector will conduct through the electrode in such a way that spatial changes in thickness or material properties will have different transient temperature responses and that the response difference will be maximum around 3-10 ms after the flash occurs. Experiments were run to test the effectiveness of the flash thermography method for detecting several different types of defects. Gross defects such as contaminants, scratches and bubbles were shown to be easily detectable. Thickness variation was also tested and shown to have a sensitivity of 1 percent change in temperature for 1 percent change in thickness. Thickness differences were shown to be detectable in at least as small as 4 percent thickness difference. Composition differences were also tested, looking at the difference in relative percentage of active material, carbon black, and PVDF. Not enough data was taken to quantify the sensitivities of composition changes, but testing was shown to be able to detect composition differences. Thermography testing also showed a wavelike thickness pattern occurring, which has not previously been reported on battery electrodes. Comparison with a commercially purchased electrode showed that this phenomenon exists on the commercial electrode as well. Further testing needs to be conducted to determine the cause of this phenomenon, but it is hypothesized that is due either to a vibration in the coater blade or a nonlinear fluid interaction of the electrode slurry. Results and analysis show that flash thermography is a viable method to detect variability and defects in battery electrodes during the manufacturing process.
Purdue has applied for a patent on the technique.
Original Writer: Emil Venere, 765-494-4709, firstname.lastname@example.org
Douglas Adams: https://engineering.purdue.edu/ME/People/ptProfile?id=12366
James Caruthers: https://engineering.purdue.edu/ChE/People/ptProfile?id=24829