Dynamic Mechanics of Micro-Crack Growth in Electrolyte-Swollen Polyolefin Separators
Electrolyte solvent plasticization lowers polyolefin yield stress, driving sub-critical micro-crack propagation under cyclic stack pressure.
Gurley Permeance
Meaning
Porous membrane characterization determines the rate of gas flow through a porous material under a specific pressure differential. Specifically, Gurley permeance measures the time in seconds required for one hundred cubic centimetres of air to pass through a square inch of separator membrane. This metric is a primary indicator of the pore structure, tortuosity and total porosity of the battery separator.
It is not used to evaluate non-porous films or dense barrier layers.
Electrochemical Resistance
Low values of this parameter indicate a more open pore structure that facilitates faster lithium-ion transport. Conversely, a high Gurley permeance suggests a restrictive pore network that increases the internal resistance of the cell. This relationship directly influences the rate capability of the battery.
Process Stability
Web coating and calendering operations can compress the pores and increase this measured value. Monitoring Gurley permeance across the production run ensures that the manufacturing process does not over-calender the separator web. This control maintains the uniformity of the active material.
Supplier Quality
Purchasing contracts for separator rolls specify acceptable ranges for this parameter to guarantee consistent cell performance. If a batch exhibits a Gurley permeance outside the limits, it is rejected to prevent imbalance between cells in a series string. This specification is crucial for high-power cell design.