Meaning
Electrochemical expansion of active materials occurs reversibly during the insertion and extraction of lithium ions within the electrode lattice. This prismatic cell breathing is the cyclic volume change and surface displacement that happens over a single charge and discharge run. Sourcing engineers must account for this phenomenon when dimensioning the compression pads that sit between cells in a battery module.
Dynamic Pressure
Anode expansion reaches its maximum at a high state of charge, exerting pressure against neighboring cells. This prismatic cell breathing generates dynamic forces that must be absorbed by compliant foam inserts. Squeezing these cells too tightly raises internal pressure and accelerates degradation.
Cell Aging
Permanent structural changes add to the reversible volume changes as the cell ages. While prismatic cell breathing is transient, solid electrolyte interphase growth contributes to a continuous, irreversible thickness increase over hundreds of cycles. The design of the pack housing must accommodate both the dynamic breathing and this long-term expansion to prevent structural bracket failure, ensuring that high-voltage seals and electrical joints are never subjected to excessive mechanical tension.
Module Design
Testing the compression profile of cell blocks under simulated service conditions reveals the peak loads on the module straps. Sourcing specifications mandate that the chosen compression pads maintain a constant pressure window despite these shifts in cell size. This pressure control ensures that the electrode stack remains under optimal compression, which extends overall cycle life.
