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.
Endplate Deflection Limits
Meaning
Maximum permissible displacement values for the rigid outer plates of a battery module define the boundary for keeping internal cell pressure within the optimal working range. Adhering to endplate deflection limits prevents the module assembly from expanding beyond its allocated volume inside the vehicle pack. These limits are determined by the strength of the structural brackets and the endplates.
Mechanical Constraint
Stiffness requirements for module endplates are calculated to resist the cumulative swelling force of multiple cells connected in series. If endplate deflection limits are exceeded, the decrease in compression allows the cells to expand, which alters their performance and can damage the high-voltage busbars. The design must balance the stiffness of the plates against the need to minimize weight.
Structural Consequence
Plastic deformation of the endplate can occur if the internal swelling force exceeds the structural design limits of the material. When the module surpasses its endplate deflection limits, the physical connection between the cooling plates and the cells is compromised due to the outward bending of the bottom corners. This misalignment creates air gaps that block heat transfer, leading to higher cell temperatures and unequal thermal distribution across the module, which accelerates localized cell aging and reduces pack safety.
Verification Method
Strain gauges and laser displacement sensors measure plate movement during simulated accelerated aging tests. The measured values are compared against the endplate deflection limits under maximum pressure.