Multilayered PCL@PEG/Al₂O₃-ADP phase change composite film with foldability, leakage-proof and flame retardancy for lithium-ion battery thermal management

The quest for ever-growing energy density of lithium-ion batteries dictates urgent concerns about their thermal safety. Phase change materials (PCMs) are considered promising for battery thermal management, yet their extensive application is restricted by inherent limitations such as leakage risk, low thermal conductivity, and flammability. Here, we fabricate a multilayered PCL@PEG/Al₂O₃-ADP (CEAD) composite film through strategy of coaxial electrospinning and dip-coating. Benefiting from the effective PEG encapsulation, thermally conductive Al₂O₃ fillers, and an ADP coating for flame retardancy, the composite film demonstrates excellent shape stability with no leakage even after 12 h of continuous exposure at 50 °C, high phase change enthalpy, improved thermal conductivity, and self-extinguishing behavior. Its notable foldability also ensures facile installation. When wrapped around a lithium-ion battery, the film maintains the battery temperature below 45 °C under a 5C discharge rate, which is 13 °C lower compared to the bare one. Thus, the composite film provides simultaneous efficient thermal management and flame retardancy, meeting critical safety requirements for high energy density lithium-ion batteries. This work offers a viable pathway for developing multifunctional thermal management materials suitable for advanced battery systems and other electronics.