Meaning
Mechanical pore compression defines the localized pressure required to collapse the open pore structure of a battery separator membrane. Specifically, pore closure pressure is the compressive stress at which the ionic pathways within the separator are squeezed shut, significantly increasing its electrical resistance. This parameter is measured in megapascals under specific temperature conditions and is determined using electrochemical impedance spectroscopy under load.
It does not apply to non-porous solid electrolytes.
Separator Integrity
High internal pressure generated by swelling active materials can exceed this threshold during charging. When the cell pressure reaches the pore closure pressure, the transport of lithium ions is severely restricted. This restriction leads to localized starvation of the electrolyte and increases the internal cell resistance.
Safety Shutdown
Specialized shutdown separators are designed to utilize this mechanism deliberately during thermal events. At elevated temperatures, the polymer softens, allowing the pore closure pressure to shut down the pore structure and stop the electrochemical reaction. This action prevents the cell from progressing to thermal runaway.
Procurement Factor
Procurement teams evaluate this pressure threshold to match the separator with the mechanical expansion profile of the selected active materials. A separator with a high pore closure pressure is selected for silicon-anode cells that generate high swelling forces. This choice ensures the cell remains ionically active throughout its operating range.
