Preparation Of PVDF-HFP Matrix Complex Micro-Porous Polymer Electrolyte Membrane

Polymer lithium ion battery (PLIB) did not only possess the advantages of high energy density, long cycle life and friendship with environment, but also had advantages of improved safety and design flexibility in cell dimension compared with the liquid electrolyte Li-ion batteries. Thus, PLIB had attracted much research attention and became a highlight of development of advanced chemical power sources in recent years. The electrolyte membrane played an important role in polymer Li-ion battery; because the performance of membrane was one of the most important factors that determine the performance of battery.In this article, inorganic nanometer materials (SiO2 and Al2O3) were used to modify PVDF-HFP matrix micro-porous polymer electrolyte membrane made by Bellcore method and phase inversion method, respectively. For the electrochemical property of the polymer electrolyte prepared in the experiment, the experiment revealed that a phase inversion method was better than a Bellcore method. The phase inversion method adopted the boiling point difference between the solvent and non-solvent to get the membrane by evaporation. This method was very simple and didn't use plasticizer.Effects of solvent's kind and the ratio of plasticizer(DBP) and non-solvent on the liquid uptake,micro-morphology,mechanism capability,ionic conductivity,electrochemical stability window of polymer electrolyte membrane were studied. The crystal structure,micro-morphology,interphase capabilities and electrochem- ical properties of this electrolyte membrane were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), FTIR, electrochemical impedance spectra (EIS), linear sweep voltammetry. The preparation technics are optimized, and the correlative effects of nanometer SiO2 and Al2O3 additives were studied.The results of the experiment indicated that the mechanism capability,ionic conductivity,ions transference number, electrochemical stability window of polymer electrolyte membrane were increased after polymer electrolyte membrane was doped by the inorganic nanometer materials, and the optimal doping concentration were both 6%.The ionic conductivity (20℃) of the PVDF-HFP/SiO2 and PVDF-HFP/Al2O3 polymer electrolyte membrane were 2.762×10-3 and 6.510×10-3S·cm-1 with ions transference number 0.80 and 0.85, and the electrochemical stability window were 5.2V and 5.8V, respectively.