Crack growth in the heat-sealed seam of aluminum - polymer laminates for pouch-type battery cells.

Abstract

An analytical-numerical model is proposed for the slow subcritical growth of a crack in the heat-sealed seam of an aluminum-polymer laminate used in pouch-type battery cells under internal pressure. The internal pressure develops during battery charging and operation as a result of gas evolution. The enclosure of such cells should be treated not as a homogeneous metallic or polymeric plate, but as a thin asymmetric aluminum-polymer laminate consisting of an outer polyamide layer, an aluminum-foil barrier layer, an inner polypropylene layer, and adhesive interlayers. Particular attention is paid to the anisotropic, elastic-plastic, and viscoelastic behavior of the enclosure. Generalized stress–strain curves, a schematic assessment of creep, and an idealized bulging profile of the enclosure are presented.The crack-growth model combines a modified Leonov-Panasyuk-Dugdale scheme with a constant prefracture-zone length, a critical crack-opening-displacement criterion, hereditary viscoelasticity of the polymer layers, an exponential cohesive law for the seam, and degradation of the fracture energy under a sustained opening force.