Preparation And Characterization Of PVDF-based Composite Gel Polymer Electrolyte

The research of polymer lithium-ion battery is in the highest level of lithium battery,which not only retains the characteristics of liquid lithium-ion batteries, but also it has theproperties of well-design, battery capacity, charge&discharge efficiency, and environmentalfriendly. In addition, because of no free liquid electrolyte in the battery, there is no fear ofthe problems of liquid leakage pollution and battery combustion for the battery.In this paper, three kinds of polymer electrolytes based on polyvinylidene difluoride(PVDF) matrix were prepared and characterized.(1) A new kind of additives SiO2(Li+),which was prepared by in-situ polymerization was doped into the composite porous polymerelectrolyte by immersion precipitation. Their morphologies were studied by SEM. Theelectrochemical performance were studied with AC impedance, linear sweep voltammetryand cell test. The results showed that the sample with5%SiO2(Li+)presents uniform surface;the corresponding ion conductivity at room temperature is4.6×10-3S/cm and theelectrochemical stability window is up to5.1V;(2) A novel ionomer polyurethane lithiumsalt (PLS) was prepared by solution polymerization and neutralization reaction, it was addedinto the PVDF matrix and the hybrid gel polymer electrolytes were prepared by by thermalphase separation. The electrochemical measurements show that the ion conductivity andlithium ion transference number of the hybrid polymer electrolyte(10%PLS) at roomtemperature is2.5×10-3S/cm and0.457, respectively. The electrochemical stability windowis up to4.95V and the corresponding cell remained89%of the initial capacity after50cycles;(3) An organic/inorganic nanocomposite SiO2-PAALi was synthesized by situpolymerization and neutralization. The hybrid nanocomposites are incorporated intoPVDF-based microporous membranes during the electrospinning process to fabricate acomposite nanofibrous membrane. Mechanical properties tests show that the electrospinningmicroporous membrane with SiO2-PAALi has a high tensile strength at48.8MPa andelongation at break with25.6%. The corresponding gel polymer electrolyte (GPE) has ahigh ionic conductivity, wide electrochemical window and good charge/dischargeperformance. The ionic conductivity of the GPE at ambient temperature is3.5×10-3S cm-1and the reciprocal dependence of ionic conductivity on temperature for GPE followsArrhenius relation. The electrochemical stability window can reach5.05V and thecorresponding cell remained96.99%of the initial capacity after30cycles due to thepresence of SiO2-PAALi. The battery properties of the assembled cells using GPE dopedwith SiO2-PAALi show excellent cycle performance.