Enhancing Polypropylene-Based Separator Efficiency in Lithium-Ion Batteries through Maleic Anhydride Addition and Corona Radiation Modification

Polypropylene-grafted-maleic anhydride (PPMA) as a modifier of polypropylene (PP) at different contents and the corona radiation for surface ionization at various modification times were applied to promote the PP-based separator efficiency. The determined microstructural characteristics showed an improvement in the separator's porosity of 6-139% at the tension amounts of 700-900%, however, more stretching hurts the mechanical properties. The electrostatic interactions formed between the electrolytes and anhydrides increased the electrolyte sorption capacity in the samples and the surface wettability by 740% and 25%, respectively. The electrical test results indicated that the anhydrides led to capturing the electrolytes in the separator and created a resistance against the ion diffusion. This phenomenon reduced the separator resistance from 475 to 165 Ω, and enhanced the charge capacity and ion conductivity from 585 to 871 mAh/g and 0.29 to 0.34 S.cm^-1, respectively, while the PPMA content increased from 20 to 60 wt.%. The achieved FT-IR illustrated that the ionization caused the creation of more polar groups in the LIB separator, which increased the bulk and surface wettability by 420% and 21%, respectively, without any change in the microstructure of the separator. However, raising the exposure time in the radiation process decomposed the sample surface and led to damage in the separator microstructure. This issue reduced the separator porosity as well as the electrolyte absorption amount and ion conductivity.