Meaning
External compression maintains uniform contact between the internal layers of a pouch or prismatic cell. Engineers apply mechanical stack pressure to prevent the delamination of electrodes and to ensure efficient ion transport across the separator. This physical load counteracts the natural expansion that occurs during charging.
Compression Force
Springs or foam pads exert a constant load on the cell faces within a module. The mechanical stack pressure must be high enough to keep the layers flat but low enough to avoid crushing the porous structure of the separator. Optimal values are determined through electrochemical testing and mechanical modeling.
Contact Resistance
Uniform pressure reduces the electrical and thermal gaps between the active materials and the current collectors. When mechanical stack pressure is insufficient, small voids form, leading to uneven current distribution and localized heating. This degrades the performance and shortens the life of the battery.
Proper distribution of the force across the entire surface area prevents the formation of dead zones where no reaction occurs. Consistent pressure is particularly important for solid state batteries that rely on physical contact for ion conduction.
Cell Life
Longevity increases when the internal structure remains stable throughout thousands of expansion cycles. Maintaining the correct mechanical stack pressure suppresses the growth of lithium dendrites and slows the thickening of the solid electrolyte interface. This leads to more predictable degradation and a longer service life.
