The Battery & Battery Separator Industry
PMI provides the battery separator industry with testing equipment and analytical services which allow researchers to predict factors such as rates of uptake of cathode/anode components (gas or liquid) by materials used to separate the two cells of a battery. PMI instruments also help researchers to predict the rates of passage and retention of ions of various sizes through separator materials. In addition, PMI instruments are utilized to test raw materials incorporated into battery cells. These materials include solids such as ZnO2 and MnO2, and a variety of common compounds. The testing described above is accomplished by a combination of techniques, the most important of which is Capillary Flow Porometry. Porometry characterizes the transport properties, or through-pores, of a separator material. It thus allows for prediction and correlation of the properties discussed above. Characterization of pore throat - by porometry allows for prediction of retention, and provides data on battery performance.
To gain total porosity information, one must look at all pores, not just the dead-end pores. Moreover, the surface structure and shape of the separator, not measured by porometry, often influence performance properties. The PMI Mercury Intrusion Porosimeter and BET Sorptometer supplement the Porometer by providing total pore characterization and surface area information. Additional information obtained through Porosimetry and BET Sorptometry includes total pore volume, surface area, and chemisorption. (Chemisorption measures the total reactive surface through "direct molecular probes".)
Surface area is also important in areas of the battery outside of the separator - namely, cell components. The reactivity of powdered components is directly correlated to the total reactive surface in the material and the size and shape of the pores. This reactivity is directly tested by the BET Sorptometer and, to a lesser extent, the ESA and the Mercury Intrusion Porosimeter. While the BET Sorptometer provides the most thorough surface area and porosity analysis, the ESA provides quick external surface area information for quality control purposes.
PMI is very active in developing new techniques to more accurately and efficiently characterize surface area and porosity. PMI has on-going research aimed to lower the testable pore size range for through-pores. To date, we have implemented a stepwise improvement from 330 Å to 135 Å - useful for the many separators that have very small pores. Additional research continues for an improved model for lower pore size and flow-based pore volume.
Our APP line of products also offers ways to test your battery casing for burst pressure. Click here for more information.