Meaning
Polymer membrane manufacturing defines the production of porous separator sheets using a phase-inversion or extraction method. Specifically, a wet process polyethylene separator is produced by mixing ultra-high molecular weight polyethylene with a liquid plasticizer, extruding the mixture into a film and extracting the plasticizer with a volatile solvent to create a highly porous, isotropic structure. This process produces a separator with high tensile strength in both directions and a uniform pore distribution.
It does not describe the dry-stretch process which produces highly oriented, anisotropic pores.
Mechanical Strength
High tensile strength in the transverse direction prevents the separator from tearing during high-speed winding and assembly. When a wet process polyethylene separator is used, it exhibits better resistance to puncture from electrode burrs or lithium dendrites. This strength improves the yield of the assembly line.
Electrochemical Performance
Isotropic pore structure provides more uniform ionic conduction across the active area of the cell. This uniform transport minimizes localized current concentration, which reduces the risk of lithium plating during fast-charging operations. The resulting cell exhibits longer cycle life.
Sourcing Advantage
Sourcing managers choose this separator type for high-performance and high-energy-density cells that require thin, reliable insulation. Although more expensive than dry-process alternatives, the wet process polyethylene separator offers superior safety margins. This preference dictates the supplier selection for automotive-grade cells.
