Comparison of mercury porosimetry and flow porometry for the testing of battery separator materials

Control of porosity is very important for proper functioning of battery separators. Specifications of mean pore size and percent porosity are commonly an integral part of separator acceptance criteria. To date most testing of these parameters has relied on mercury intrusion porosimetry. A new technique, flow porometry, has been introduced which has the potential of more accurately predicting product performance. This technique categorizes pore structure based on flow rates through the membrane and is specially useful in locating pore structure defects, which can be a chief cause for product failure, and malfunctioning. Data from both mercury intrusion and flow porometry analyses on different types of separator materials are critically examined and discussed. It is proposed that the battery industry could benefit by using information created by flow porometry to augment its reliance on mercury porosimetry data.