Abstract

During high-speed stacking in commercial lithium-ion battery (LIB) manufacturing, electrode sheets can fracture, generating electrode fragments (hereafter referred to as scrap) that may remain inside the cell as latent defects. Despite their practical relevance, the electrochemical and safety implications of such scrap have not been systematically elucidated. Here, we fabricate pouch-type LIBs containing cathode scrap of controlled sizes and investigate their electrochemical behavior. While scrap-containing cells exhibit discharge capacities comparable to those of scrap-free cells during initial cycling, cathode scrap locally inverts the negative-to-positive electrode capacity ratio (N/P ratio), thereby promoting dendritic Li growth near the scrap edges. At moderate C-rates, the impact of cathode scrap on capacity retention is negligible. However, under fast-charging conditions, the presence of scrap leads to a pronounced increase in overpotential, which scales with scrap size and accelerates capacity fading. Electrochemical modeling reveals that cathode scrap elevates local resistance, creating hotspots that promote dendrite growth. Our findings demonstrate that high-power cycling yields quantitative indicators of scrap-induced degradation, and that rapid, non-destructive X-ray radiography enables reliable identification of scrap-containing cells, thereby ensuring the safety of commercial LIBs.