Controlled Electrode Delamination for Degradation Analysis in Fault-Simulated Li-Ion Batteries

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Lithium-ion batteries (LIBs) are widely used in portable electronics, electric vehicles, and energy storage systems due to their high-energy-density. In this context, many researchers have developed high-mass-loading electrodes with reduced binder content to increase the proportion of active material. However, this design introduces mechanical challenges, particularly a reduction in adhesive strength, which is critical for maintaining electrode integrity during cycling. These challenges become more pronounced under extreme conditions, such as fast charging/discharging, elevated temperatures, or prolonged cycling, where weak adhesion can lead to delamination between the electrode layer and the current collector. Delamination is a critical issue in LIBs because it disrupts the electron/ion transport pathways, leading to uneven current density and increased interfacial resistance. Various approaches have been explored, including the use of advanced polymer binders with higher adhesive strength and flexibility. However, Latent delamination defects, which manifest subtly during LIB operation, remain a significant challenge. In this study, we propose a novel fault-simulation method to investigate the effects of latent delamination in LIBs. Paraffin wax, a low melting-point material, was incorporated into electrodes to simulate defects. During high-temperature cycling, the wax melts, creating intentional delamination between the electrode and current collector. These fault-simulated batteries (FSBs) allowed us to study how delamination affects current distribution, interfacial resistance, and overall cell performance. Using non-invasive magnetic field imaging (MFI), we successfully detected areas of uneven current density caused by delamination, providing a reliable diagnostic tool for monitoring defects. Furthermore, we analyzed how the location of defects, whether near the top or bottom of the electrode, affects cell performance. The results showed that interfacial adhesion plays a critical role in maintaining stable cycle performance. By combining fault-simulation techniques with advanced diagnostic tools like MFI, this study provides a comprehensive approach to understanding and mitigating the challenges posed by hidden defects in commercial LIBs.

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