Standard Equivalent Air Leak Rate Conversions for Sealed Commercial Pouch Cells
Standard air equivalent leak conversions transform empirical helium mass spectrometer readings into precise air ingress and solvent loss metrics for pouch cells.
Electrolyte Solvent Dryout
Meaning
Vaporization of volatile organic liquids from an electrochemical cell reduces the internal ionic conductivity. This physical degradation is known as electrolyte solvent dryout, and it occurs primarily when cell seals are imperfect or subjected to prolonged thermal stress. The process depletes the carrier fluid necessary for lithium transport between the electrodes.
It represents a permanent degradation mode from which a lithium cell cannot recover.
Primary Cause
High temperatures and seal imperfections accelerate the evaporation of the solvents. When cells operate near their thermal limits, the local pressure increases, driving electrolyte solvent dryout through microscopic openings. Polymeric seals degrade under these conditions and become more permeable over time.
This depletion is also exacerbated by overcharging events.
Failure Mechanism
Loss of solvent increases the concentration of salts and raises the internal resistance. Liquid depletion during electrolyte solvent dryout leads to uneven current density across the electrode surfaces. This uneven flow triggers localized lithium plating during fast charging cycles.
As the active areas dry, the cell experiences a rapid decline in usable capacity and eventually ceases to function because of the high internal resistance. The resulting dry regions can also create localized hotspots that increase the risk of thermal runaway under load.
Commercial Risk
Procurement contracts define strict seal weight loss limits to prevent premature battery death. Sourcing departments utilize thermal chamber aging to predict electrolyte solvent dryout in prospective cell designs. Cells with high solvent retention are selected for heavy-duty industrial applications.
This screening prevents expensive warranty claims from early field failures.