Meaning
Physical retreat of the liquid electrolyte from the pores of a polymer membrane creates inactive regions within a battery cell. Occurrence of separator de wetting leads to non-uniform current distribution and localized hotspots during charging. This phenomenon is often driven by gas evolution or a lack of surface compatibility between the liquid and the porous plastic.
Surface Tension
Mismatch between the surface energy of the polyolefin material and the electrolyte prevents the fluid from maintaining a stable interface. If the internal pressure rises due to gas generation, separator de wetting can occur as the gas displaces the liquid from the smallest capillaries. High temperatures further reduce the wetting stability by altering the chemical properties of the solvent.
Impedance Rise
Electrical resistance increases markedly in areas where the ionic pathway is broken. Because separator de wetting removes the conductive medium, the ions must take a longer path through the remaining wet areas. This congestion causes the local current density to spike, which may accelerate the growth of lithium dendrites in those regions.
Thermal Impact
Non-uniform heat generation across the electrode surface shortens the overall lifespan of the battery. Preventing separator de wetting requires the use of surfactants or ceramic coatings that enhance the hydrophilicity of the membrane.
