Quantifying Micro Leak Thresholds for Lithium Ion Envelope Integrity Assurance
Micro leak rates above 1.0e-6 mbar L/s drive moisture ingress and hydrofluoric acid formation, degrading lithium ion cell capacity and triggering transport failure.
High-Voltage Spark Testing
Meaning
Quality control procedure that applies a brief electrical potential across a barrier material to detect microscopic physical defects or thin spots. This test determines the insulation integrity of pouch foils, plastic casings, or separator materials before cell filling. Standard operating procedures rely on high-voltage spark testing to prevent short circuits during the service life of a battery.
Dielectric Breakdown
The principle of the test relies on the electrical resistance of the insulating material being tested. Under normal conditions, the polymer layer resists the applied voltage, preventing current flow. If a pinhole or microscopic crack exists, the high voltage overcomes the air gap or thin polymer, creating a localized electric arc.
This spark causes a detectable current surge that triggers the automated rejection mechanism.
Inline Inspection
High-speed automated production lines incorporate this test directly into the winding or pouch forming stage. The material passes between a conductive roller and a high-voltage brush electrode, enabling rapid continuous screening of the moving web. Implementing high-voltage spark testing at this point prevents defective packaging from moving to the electrolyte filling station, which saves chemical materials and reduces manufacturing scrap costs.
Reject Threshold
The applied test voltage must be calibrated to ensure it is high enough to find defects without damaging the healthy polymer substrate. Too high a voltage causes dielectric breakdown of flawless material, whereas too low a voltage misses critical pinholes. Sourcing specifications define the maximum allowed leakage current during high-voltage spark testing to ensure that only pouch materials with uniform dielectric strength are accepted.