Modification of Lithium Ion Battery Separators by Electron Beam Radiation Induced Grafting of Glycidyl Methacrylate onto Porous PP Film

In order to modify porous polypropylene (PP) film which is used as separator of lithium ion battery, monomers glycidyl methacrylate (GMA) with epoxy groups were grafted onto porous PP film by electron beam induced pre-irradiation technology. Firstly, the influences of reaction conditions such as concentration of monomer, absorbed dose and temperature on grafting yield were carried out. Secondly, the prepared graft copolymers PP-g-GMA were assembled to Lithium ion battery to make clear the influence of modification of PP film on the property of Lithium ion batteries. The performance test of Lithium ion battery showed that battery assembled with the grafted PP of grafting yield 68.4% exhibited higher capacity and better cycling performance. Grafted PP with different grafting yield was characterized by FTIR and differential scanning calorimetry technique. All results further confirmed modification of porous PP film. The research provided a facile and effective way for introducing poly glycidyl methacrylate (PGMA) chains onto PP film. Compared to the original PP separators, the grafting of PGMA chains onto PP improved the affinity between the grafted PP and liquid electrolyte, which benefited the increase of separators performances.