Meaning
Physical displacement occurring within an electrochemical cell as it expands and contracts during charge and discharge cycles. The phenomenon of cell breathing strain arises from the insertion and extraction of ions within the active electrode materials, particularly silicon or graphite. Designers must accommodate this transient volume change to prevent mechanical failure within the pack enclosure.
Mechanical Response
Cyclic mechanical stress occurs as the internal layers push against the constraints of the module housing. This behavior differs from long-term swelling, which accumulates over the lifetime of the battery due to chemical degradation and solid electrolyte interphase growth. The temporary displacement repeats with every charge event, creating a dynamic mechanical environment.
Pressure Measurement
Monitoring the localized force requires placing compression pads or load cells between individual pouches. A typical cell breathing strain profile shows a rise in compression force at high states of charge, which then relaxes as the energy drains. Engineers use these data points to size the springs and foam cushions that stabilize the cell stack.
If the structural restraint is too rigid, the resulting localized force can damage the separator, leading to an internal short circuit.
Degradation Risk
Acceleration of lithium plating is a common consequence of excessive pressure spikes. The mechanical constraint alters the transport of ions through the electrolyte, leading to uneven current distributions. This issue decreases cell lifetime and increases the likelihood of thermal runaway.
