Automated Meter Mix Dispensing Dynamics for Thermally Conductive Gap Fillers
Volumetric displacement precision, shear rate thermal control, and wear-resistant fluid metering govern automated thermal gap filler dispensing performance.
Outgassing Micro Voids
Meaning
Electrode imperfections occur when volatile solvents vaporize rapidly during the high-temperature drying phase of the manufacturing process. These tiny, internal cavities, known as outgassing micro voids, form when solvent gas cannot escape before the binder matrix solidifies. They weaken the mechanical adhesion between the active material and the metal current collector, creating zones of high contact resistance.
This defect does not develop when drying temperatures are ramped slowly to allow the solvent to evaporate gently.
Defect Formation
Rapid heating causes the slurry solvent to boil, creating vapor pockets that push the active material particles apart. During this rapid drying, the formation of outgassing micro voids occurs primarily in the deeper layers of the electrode near the foil substrate. High wet-thickness coatings are particularly susceptible because the diffusion path for the vapor is longer and more restricted.
This localized separation reduces the electrical and ionic pathways within the composite electrode.
Inspection Method
High-resolution imaging and density measurements identify these microscopic hollow spaces within the dried electrode structure. While outgassing micro voids are invisible to the naked eye, they can be detected using scanning electron microscopy on cross-sectioned electrode samples. Ultrasonic testing and electromagnetic thickness gauges also reveal localized decreases in coating density and cohesion.
Detecting these anomalies early allows manufacturers to adjust the temperature profiles of the drying ovens. If the drying speed is kept too high without corrective intervention, the overall adhesion of the active material can drop below the minimum quality threshold, forcing the rejection of entire rolls of expensive coated foil.
Performance Impact
Degraded energy density and accelerated aging result from the compromised internal structure of the electrode. The presence of outgassing micro voids reduces the effective contact area between the active materials and the current collector, causing localized hot spots during high-current operation. These hot spots accelerate the degradation of the electrolyte and can lead to localized lithium plating.
Ensuring void-free electrode coatings is therefore essential for achieving long cycle life and high power capability.