Prismatic Cell Enclosure Mechanical Stress Distribution under Solid-State Anode Expansion
Prismatic solid-state cell enclosures demand module preloads between 2 and 8 MPa with flexible interlayers to control wall deflection and dendrites.
Microcellular Polyurethane Shims
Meaning
Foamed elastomeric spacers featuring a high density of microscopic cells provide the compliant force necessary to control cell expansion in lithium-ion battery modules. Utilizing microcellular polyurethane shims ensures that the expansion of the pouch or prismatic cells does not damage the surrounding module frame. These components are selected for their excellent energy absorption and compression recovery.
Physical Performance
Stress-strain behavior of these open-cell or closed-cell foams allows them to compress to a fraction of their original thickness without a massive spike in counterforce. When microcellular polyurethane shims are inserted, they maintain a relatively constant pressure even as the cells swell during charging. The material is designed to operate over a wide temperature range.
Functional Consequence
Inadequate cell containment occurs if the selected spacers are too soft or lose their thickness over time due to continuous mechanical stress. If the microcellular polyurethane shims fail to exert sufficient counterpressure, the active material within the cells can delaminate from the current collectors, which leads to a loss of ionic pathway continuity and a drop in overall round-trip efficiency. Furthermore, the absence of uniform support can lead to the formation of localized lithium dendrites, which can pierce the separator and cause an internal short circuit.
Material Specification
Density and compression force deflection curves are the main parameters used to choose the correct foam grade. Engineers select microcellular polyurethane shims based on these performance metrics.