Study On Preparation Of Alkaline Battery Separator By Wet-laid Process

The main cause for developing various types of clean cars such as fuel-cell vehicles and electric ones is an environmental issue. Among clean cars, a hybrid electric vehicle(HEV) with a rechargeable battery is considered to be the most promising and, therefore,has been receiving much attention. However, the battery of a HEV must have an excellent output power, high capacity, and long life and so on. Alkaline battery is one of the power supplies of a HEV with its excellent performance. Therefore, the high-performance alkaline battery is paid more and more attention. The separator is one of the important factors that affect the performance of the battery. Thus, the research and production of high-performance separator are particularly important.In this paper, the polypropylene (PP) fibers and polyethylene/polypropylene bicomponent sheath-core structure (i.e., ethylene-propylene side by side, ES) fibers were used as raw materials, and the high uniformity and high-quality alkaline battery separators were prepared by using the wet-laid process. First of all, the morphological characteristic of PP and ES fibers were analyzed. Then, the effect of the adding amount of the ES fibers on both the sheets making using the PP fibers and ES fibers and the ES fibers content on the properties of the obtained separator was explore. To improve the tensile strength and alkali absorption rate of the separators, the temperature and pressure in the hot-pressing were optimized. In addition, the disintegration revolutions, different types of additives and the furnish of fibers were investigated to get the high tensile strength and high-quality separators. Finally, using concentrated sulfuric acid as sulfonation agent to treat the battery separator in order to improve its hydrophilicity of the separatorsThe results showed that the average diameters of the ES and PP fibers were 14.1 μm.and 2.06 μm, respectively. Thus, adding the ES fibers affected the pore size and porosity and other performance of the separators. The wet-laid handsheets with a better formation could be found when the addition amount of the ES fibers exceeded 20%. The optimum hot-pressing pressure and hot-pressing temperature were 0.5 MPa and 135 ℃, respectively.Because the effective bonding between fibers of the handsheet was improved, the tensile strength of the handsheet was increased.In addition, the sedimentation volume of fibers and the tensile index of the resulted separators increased with the increase of the disintegration revolutions, and then maintained stable gradually as the disintegration revolutions exceeded 45000 r. Moreover, the addition of water-soluble polymer PEO, CMC and PAM improved the fiber dispersion and enhanced the strength of the separators, and finally the PEO of 1.5% (on oven-dry fibers) was selected and added into the fiber suspension. The strength, pore size, alkali absorption rate,and air permeability of the resulted separators showed an upward trend when the ES fibers were added in the separators. When the content of the ES fibers was 45%, the resulted separators still met the requirement of an alkaline battery separator. When the separators were treated using concentrated sulfuric acid to improve the hydrophilic property, the optimum sulfonated time was about 15 min.