Li-Ion Battery Electrode Contact Resistance Estimation by Mechanical Peel Test

Abstract

Li-ion battery electrode electronic properties, including bulk conductivity and contact resistance, are critical parameters affecting cell performance and fast-charge capability. Contact resistance between the coating and current collector is often the largest electronic resistance in an electrode and is affected by chemical, microstructural, and interfacial variations. Direct measurements of contact resistance and bulk conductivity have proven to be challenging. In their absence, a mechanical electrode peel test is often used to compare adhesion and electrical contact resistance. However, using a micro-flexible-surface probe, contact resistance can be directly determined. This work compares contact resistance and mechanical peel strength of multiple commercial-grade HE5050 and NCM523 cathodes and graphite and silicon anodes. It was found that peel strength correlates well with contact resistance in a carefully curated data set (p < 0.05) and in some situations may be a good metric to estimate electrical properties. However, there were distinct outliers in the data set, indicating that peel strength may not accurately reflect electrical properties when there is significant variation in electrode composition. These results illustrate the value of the micro-flexible-surface probe in quantifying contact resistance and bulk conductivity to better understand how battery composition and processing steps affect microstructure and resulting cell performance.

The Effects of Lithium Ions and pH on the Function of Polyacrylic Acid Binder for Silicon Anodes

“…The electrode portion underneath the adhesive tape was removed from its current collector by pulling the tape at constant displacement rate of 500 mm min −1 as described more fully in Ref. 15. The applied force was measured, and load/displacement plots were generated to analyze the results.…”

Comparison of Electronic Resistance Measurement Methods and Influencing Parameters for LMFP and High-Nickel NCM Cathodes

“…With higher degrees of particle anchoring, the peel strength is increasing. Therefore, it is possible, under certain limitations (same formulation, similar CAM), to use the peel strength as a rough proxy for the electronic resistance of a cathode [38]. Even though there were significant differences in peel strength, all coatings had sufficient adhesion on the CC.…”