The Effect of Silica Addition on the Microstructure and Properties of Polyethylene Separators Prepared by Thermally Induced Phase Separation

摘要

Novel composite polyethylene (PE) separators were prepared via thermally induced phase separation using SiO_2 as the inorganic dopant and dioctyl phthalate as solvent. Through the control of silica content, the microstructure, thermal and crystalline properties, electrolyte uptake, thermal stability, and mechanical properties of the as-prepared separators were investigated. The results showed that the doped silica particles favored the formation of the large pore size. The crystalline degree of PE was enhanced when doping silica in the ternary system below 3 wt %. The liquid electrolyte uptake was increased from 30.2% to 63.2% with doping silica content at 5 wt % in the mixed system, which benefits from the large pore size structure and the hydrophilicity of silica. The thermal decomposition temperature of the composite PE separators is 40℃ higher than the pure PE separator due to the steric stabilization and the more stable space structure induced by the doped silica. The tensile strength was increased from 12 MPa to 13.3 MPa when doping 1 wt % silica, but decreased with further silica addition.