Meaning
Structural deformation in cylindrical and wound prismatic cells often develops as a distortion of the spiral-wound electrode assembly. This jelly-roll buckling occurs when radial compression stresses exceed the mechanical stability of the electrode layers.
Deformation Force
Mechanical forces during lithiation drive the expansion of the silicon or graphite anode, which exerts pressure against the outer steel casing. If the wound core cannot expand outward, it forces the inner layers to deform inward. This jelly-roll buckling creates irregular ripples in the separator, which can disrupt the uniform flow of lithium ions.
Safety Hazard
Separator damage is the most critical consequence of these distorted winding layers. When the local stress concentrated by jelly-roll buckling breaches the thin polymeric membrane, direct electrical contact between the anode and cathode is established. This contact triggers localized heating, which can progress to thermal runaway under high-state-of-charge conditions.
Standard safety audits use computed tomography scanning to detect these hidden deformities prior to cycling.
Manufacturing Tolerance
Precise control during the cell assembly process minimizes the risk of structural failure under cycling stress. Sourcing specifications must define the winding tension profiles and the core mandrel diameter to prevent loose inner turns. These strict parameters ensure that the cells survive both high-current testing and long-term usage.
