A Novel Approach to Electrode Delamination for Mechanism Analysis and Signal Detection: Fault-Simulated Li-Ion Batteries

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The demand for increasing energy density of lithium-ion batteries (LIBs) continues to drive research into new compositions and designs. Some prominent strategies are to reduce the content of inactive materials, such as binders and conductive materials, and to increase a thickness of electrodes. However, these approaches can lead to uneven binder distribution and delamination of electrode layers due to the continuous volumetric expansion of the active material reducing the capacity and lifespan of the LIBs. Therefore, binder content and distribution analysis plays a critical role in evaluating battery performance. However, most extensive research has focused on improving the properties and distribution of binders, and systematic analysis and non-destructive detection of defects by binders remain largely unexplored. This research also is crucial for evaluating the remaining life of the battery and determining its suitability for reuse. In this study, we fabricated a fault-simulated electrodes which can be easily delaminated during electrochemical reactions. When the morphology and composition of the electrode were analyzed, there were no significant morphological differences compared to a normal electrode, but it was observed that the binder compositions were different. As a result of the adhesive strength measurement of the defected electrode at different thicknesses, it was demonstrated that the adhesive strength at the electrode layers and interfaces decreased compared to normal electrodes. The electrochemical signals such as capacity fading and resistance characteristics by the electrode delamination were confirmed. Through the post-mortem analysis, the composition change in the cathode-electrolyte interphase (CEI) inside the electrode was compared and analyzed in relation to the change in current density distribution based on simulation. Furthermore, in order to nondestructively detect the electrode delamination defects, a magnetic field imaging and simulation analyses were conducted, and it was confirmed that the detection of defect spots was possible through this method. By systematically analyzing the electrode delamination, the main cause of electrode degradation was elucidated.