Meaning
Processing steps during electrolyte infusion and pouch cell vacuum sealing introduce unevacuated pockets of gas within porous electrode matrices and separator layers. In battery production lines, gas entrapment occurs when ambient air or solvent vapors fail to escape before sealing. Undetected gas pockets alter local current density distribution during initial formation cycling.
Proper evacuation procedures reduce void formation to maintain uniform electrochemical activity across entire electrode surfaces.
Ionic Impairment
Trapped void spaces prevent liquid electrolyte contact with active anode and cathode materials. Experiencing gas entrapment creates isolated non-conductive zones where lithium ions cannot intercalate into the host crystal lattice. Localized current density spikes along the perimeter of dry areas accelerate local heating during rapid charge cycles.
Over time, uneven current distribution triggers localized metallic lithium plating on graphite surfaces. Plated lithium increases cell internal impedance and elevates internal short circuit risk during extended operation.
Cell Degassing
Vacuum pressure cycles applied before final pouch sealing extract residual gas bubbles. Pouch cells undergo intermediate degassing steps after formation cycling to remove electrochemical reaction byproducts. Mechanical pressure rollers squeeze mobile gas pockets toward designated pouch headers prior to secondary sealing.
Surface Degradation
Non-uniform wetting causes localized degradation along un-wetted electrode interfaces. Gas pockets alter interfacial resistance across separator surfaces. Incomplete contact accelerates local cathode capacity loss over extended cycling.
