Electrochemical Performance And Preparation Of Electrospun PVDF/PMMA Membranes For Lithium Ion Battery

In the era of rapid development of information and electronics industry, lithium ion batteries are widely used in cellular phones, military affairs, wireless communications equipments and many other areas for their high specific energy, high operating voltage, low self-discharge and wide temperature range, and toward to intelligent, compact, environmentally orientation. Polymer lithium ion batteries use polymer electrolyte instead of liquid electrolyte, overcome the safety problems of leakage, and the use of plastic film packaging, and greatly increased the flexibility in battery design. So they become an important research direction in lithium ion batteries.In this paper, fibrous membranes based on poly(vinylidene fluoride)/poly(methyl methacrylate) (PVDF/PMMA) were fabricated via electrospinning method. Its preparation technology and physics and electrochemical properties have been studiedThe main contents were as follows:Firstly, three typical morphology fibrous membranes of PVDF/PMMA were fabricated by electrospinning with different concentrations of polymer solution. And discuss the selection of parameters. The membranes were investigated using scanning electron microscopy (SEM), fourier transform infrared (FTIR), differential scanning calorimetry (DSC), porosity, uptake of electrolyte, conductivity and other tests. The results showed that with the 16 wt.% concentration of the polymer solution, the fibrous membranes exhibited uniform fiber diameter, excellent electrochemical stability, highest ionic conductivity, and reach 3.5×10^-3 S/cm at room temperature. Secondly, fibrous membranes of PVDF and PVDF/PMMA with different polymer mass ratio were preparation by electrospinning. The membranes were investigated using SEM, FTIR, X-ray diffraction (XRD), conductivity, interface stabilities and other tests. The charge/discharge measurements were carried out with Li/LiFePO₄ cells by using PVDF/PMMA (8/2) as polymer electrolyte. The results showed that the solution of PVDF/PMMA can be electrospun with different polymer mass ratio; PVDF/PMMA (8/2) exhibited low crystallinity, high uptake of electrolyte, high ionic conductivity. And Li/LiFePO₄ cell based on PVDF/PMMA (8/2) polymer electrolyte showed a first discharge capacity of 153.3 mAh/g at 0.1 C-rate and exhibited good cycle performance.Finally, adding the precursor of titanium dioxide (TiO₂) in polymer solution and fabricated PVDF/PMMA/TiO₂ membranes via electrospinning method. The membranes were investigated using SEM, FTIR, DSC, conductivity and other tests. The results showed that TiO₂ can be evenly distributed in nanofibers; PVDF/PMMA/TiO₂ membranes exhibited low crystallinity, excellent electrochemical stability, high ionic conductivity of 3.87×10^-3 S/cm at room temperature.