PP/PE/PP Trilayer Composite (Celgard M825) Disc & Roll (T=16 um) as Battery Separator, CBSTPCM825

Celgard® M825 is an ultra-thin 16 µm dry-process trilayer microporous membrane (PP/PE/PP) designed as a safety separator for high-energy-density lithium-ion and advanced rechargeable battery systems. By sandwiching a polyethylene (PE) core between two outer polypropylene (PP) layers in a slim 16 µm profile, it delivers thermal shutdown safety, high oxidation resistance, and low cell internal impedance. 

The main features of the 16 um PP/PE/PP composite separator are: (1) Thermal Shutdown Safety (PE Core): The internal polyethylene layer melts at approximately ~ 130°C, closing the micropores and blocking ionic transport to interrupt current flow during thermal runaway risks. (2) High Melt Integrity & Oxidation Resistance (PP Outer Shells): The outer polypropylene layers have a higher melting point (~ 165°C) to preserve physical separation between electrodes, while offering high oxidative stability against high-voltage cathode surfaces. (3) Zero TD Shrinkage: Manufactured via Celgard’s dry uniaxial stretching process, the membrane exhibits 0.0% transverse direction shrinkage at elevated temperatures, preventing edge curling and internal short circuits. (4) Volumetric Energy Density: At 16 µm, M825 allows for higher active material loading compared to standard 20 µm (e.g., Celgard 2320) and 25 µm (e.g., Celgard 2325) trilayer separators.

References: 

1. W. D. Hsu, et al. Preferential lattice expansion of polypropylene in a trilayer polypropylene/polyethylene/polypropylene microporous separator in Li-ion batteries, Scientific Reports, 2021, 11, 1929.
2. Y. Li, et al. Polypropylene/polyethylene multilayer separators with enhanced thermal stability for lithium-ion battery via multilayer coextrusion, Electrochimica Acta, 2018, 264, 140-149.