Abstract Lithium batteries represent a pivotal technology in modern energy storage and have attracted significant attention. Copper foil is frequently employed as the current collector for the negative electrode; however, the presence of micro-defects can severely impair the electrochemical performance of lithium batteries. Therefore, developing a method that can accurately detect micro-defects during high-speed production processes and subsequently achieve precise quantification of defect sizes is of paramount importance. Motion-Induced Eddy Current (MIEC) techniques, characterized by relative motion, can detect defects in conductive materials during high-speed movement. However, no research has been conducted on defect size quantification based on motion-induced eddy current signals. Consequently, this study proposes a quantification method for micro-defect size in copper foil based on motion-induced eddy current signal characteristics. By combining wavelet soft-thresholding and morphological filtering, high-frequency noise and signal fluctuations caused by variations in lift-off distance are effectively removed from the measured signals. Additionally, eight different features are defined for the micro-defect motion-induced eddy current signals, and a feature dataset for various sizes of copper foil micro-defects is established under different motor speeds. The proposed IVY-CNN-BiLSTM-Attention model is then utilized for the quantification of micro-defect sizes, yielding excellent results.
Read full abstract