Mechanical Restraint

Expansion Control

Rigid plates made of aluminum or steel apply a constant counterforce to the face of the battery. Without this mechanical restraint, the electrodes would move apart as ions intercalate into the host lattice.

Cycle Performance

Long term stability of the lithium ion chemistry depends on keeping the active materials in close proximity. Effective mechanical restraint slows the rate of capacity fade by preventing the formation of cracks in the electrode structure and maintaining the integrity of the solid electrolyte interphase.

Safety Margin

Compression systems must account for the increasing thickness of the cell over its entire operating life. Designers calculate the stiffness of the mechanical restraint to balance the need for high pressure against the risk of crushing the internal components during a high temperature excursion. Excessive force can squeeze the electrolyte out of the separator or cause plastic deformation of the current collectors.