Preparation and characterization of gel polymer electrolyte based on porous poly(methyl methacrylate) and poly(vinylidene fluoride) films for lithium ion batteries

The porous composite polymer films (PMF-template-HF) based on the blending of poly(methyl methacrylate) and poly(vinylidene fluoride) (PMF) were prepared by template method. The effects of the template (SiO2 and SBA-15) on the properties of the composite polymer films (PMF-template) and PMF-template-HF including morphology, porous structure and thermal properties, as well as the electrochemical properties of the composite films based gel polymer electrolyte (GPE) are studied. XRD results indicated that all the composite polymer films are amorphous polymer. The mass fraction of template in the PMF-template was 2.67% ~ 2.78%, and the introduction of the template could increase the membrane porosity, ionic conductivity and lithium ion transference numbers of the GPE. Moreover, acid could dissolve some template and the mass fraction of template in the PMF-template-HF was 0.89%~1.77%. Acid treatment could further increase membrane porosity, ionic conductivity and lithium ion transference numbers. The cell with PMF-template-HF membrane showed best battery performance, followed by the cell with PMF-template membrane and PMF. The columbic efficiency of the PMF-template and PMF-template-HF membrane based battery closes about 99.7% during the 100 cycles, while columbic efficiency of the Li/PMF/LiFePO4 battery was 96.1%.