Meaning
Mechanical deformation process in which microscopic voids within a ductile material expand under localized tensile or gas pressure stresses governs the breakdown of soft solid structures. This action, known as plastic void inflation, occurs when the yield strength of the surrounding metal or polymer matrix is exceeded by internal pressure. It reduces the density and electrical conductivity of the material, leading to premature mechanical failure.
Mechanical Behaviour
During electrochemical cycling of lithium metal anodes, non-uniform metal stripping can leave behind tiny micro-voids in the metal. If localized mechanical stresses or trapped gases exert pressure on these cavities, the surrounding lithium deforms plastically, causing the voids to grow and coalesce. This creates a highly porous, low-density lithium structure that degrades the mechanical contact between the anode and the solid electrolyte.
Sourcing Quality
Sourcing guidelines for separator membranes and polymer-based protective layers require specific tensile strength limits to resist this form of void growth. Separators must maintain structural integrity under the high localized pressures that occur when gases accumulate. Sourcing teams select polymers with high resistance to plastic deformation to ensure that the cells do not suffer from internal short circuits caused by separator tearing.
Stack Pressure
External mechanical force applied to the cell during cycling can suppress the expansion process by counteracting the internal tension. This pressure must be kept below the mechanical yield limit of the active layers to prevent cell crushing.
