Industry-Scalable Interfacial Design for Stabilizing PET-Cu Current Collectors

Metallized plastic copper (Cu) current collectors (CCs), featuring a sandwich structure with polymer film-typically polyethylene terephthalate (PET)-as substrate and conductive Cu layers on both sides, offer a lighter and cheaper alternative to conventional Cu CC for lithium-ion batteries (LIBs). However, the instability of PET substrate in commercial carbonate electrolytes leads to Cu||PET interfacial degradation and capacity fading, particularly under high-temperature operation. Here, we report an industry-scalable interfacial engineering strategy to stabilize PET substrate by depositing an Al₂O₃ layer onto the PET substrate surface via roll-to-roll physical evaporation (winding speed: 720 m min^-1, substrate width: 2.5 m). The conformal Al₂O₃ coating acts as a robust physical barrier that effectively suppresses electrolyte-induced PET substrate decomposition and maintains Cu||PET interfacial integrity during long-term cycling. The as-resulting Al₂O₃-coated PET-Cu CC (PET@Al₂O₃-Cu CC) enables 3-Ah graphite//LiNi_0.5Co_0.2Mn_0.3O₂ pouch cells an 86% capacity retention after 1000 cycles at 45°C-comparable with the cells with commercial Cu CC (86%) and markedly superior to those using PET-Cu CC (58%). This work establishes a low-cost and industry-scalable solution for stabilizing metallized plastic CCs, paving the way toward cost-efficient and high-energy LIBs.