Meaning
Permanent, irreversible increase in the physical dimensions of an electrochemical cell over thousands of charge and discharge cycles. The occurrence of volumetric creep is caused by the accumulation of chemical decomposition products, such as the solid electrolyte interphase, and the mechanical restructuring of the electrodes. Pack designers must calculate this long-term growth to ensure the enclosure does not burst or squeeze the cells excessively.
Material Degradation
Deformation occurs as particles within the electrode fracture and detach. This decay is accelerated by high-temperature operation, which increases the internal stresses.
Pack Accommodation
Mechanical constraints must be engineered to absorb this expansion over the operating life of the pack. Compressible materials like foam pads are inserted between cells to distribute the forces evenly as the cells grow. If the design does not account for this expansion, the mechanical pressure can crush the cell internals, leading to premature failure.
Lifetime Impact
Capacity retention is closely linked to the physical state of the cell layers under this pressure. While some compression is necessary to maintain contact between the active materials, excessive force from constrained growth accelerates capacity loss. Sourcing contracts often specify the maximum allowable thickness increase at the end of life to guarantee the battery remains compatible with the housing.
