| Gel polymer electrolyte was the chunnel that promised the Li-ion across through in Li-ion batteries. A lithium battery using polymer electrolyte not only exclude a potential risk of fire in case of leakage of the non-aqueous electrolytic solution outside the battery by any chance due to a high pressure and ready ignitability of the electrolytic solution, and avoid the dendritic crystal growing, but also own a higher conductivity than the solid lithium electrolyte. Up to now, a series of polymer materials have been developed and used as the electrolyte in Li-ion batteries widely. High ionic conductivity and low interfacial resistance are important to a kind of ideal gel polymer electrolyte, and the polymer's crystallinity is a very important factor that affects the gel polymer electrolyte's conductivity. Poly(vinylidene fluoride ) is usually used in the polymer electrolyte for its high specific inductive constant. However, vinylidene fluoride polymer is a crystalline polymer having a crystalinity of ca.50%, so the ionic conductivity at a crystalline portion is considered to be very low because of extremely poor molecular movability of Li-ion at the crystalline portion in polymer. For this reason, a solid polymer electrolyte using a copolymer of vinylidene fluoride and hexafluoropropylene have a lower crystalinity and a higher conductivity for the lower crystallity, however, the toxic gaseous Freon will release to the air and destroy the ozone layer when the electrolyte material is burned. That's to say, the out of date used up batteries based on the fluoric-contained electrolyte will take the trouble to the circumstance. Poly(methyl methacrylate) is a amorphous polymer and has a low specific inductive constant, also it is the low-cost and synthesized easily, and so on. The merits of PMMA provide us a chance to explore a new kind of gel polymer electrolyte.In this experiment, methyl methacrylate was used as the starting material tosynthesize poly(methyl methacrylate), and benzoyl peroxide was used as initial agent for polymerization. Synthesized complex wahshed by the deionized water was dried and pressured at 80°C and under -0.7X 105Pa, then the dried macrololecule of PMMA and PVdF were mixed in the tetrahyduofuran and stirred, and cast on a glass sheet , followed by standing for 1 hour at room temperature so as to evaporate the tetrahydrofuran. The target solid film was formed. The film was dried in vacuum drying oven under reduced pressure at 60°C for 24 hours, and then transfered to the glove box. The gel polymer electrolyte was prepared by impregnating PVdF .PMMA complex film with lmol-L"1 LiPF6 organic solution(EC/DMC=l:l, bulk ratio) for 30 min. The transparent gel polymer matrix exhibits both an appropriate level of ionic conductivity in its state of being swollen with a non-aqueous electrolytic solution and excellent adhesion to an electroconductive substrate, retentivity of powdery electrode materials, excellent heat resistance.FT-IR(FT-IR spectrometer Nexus 470/670/870, made in the U.S.) measurements were made between the range 400cm"1 and 4000cm"!, X-ray diffractometer(D/MAX-III B) were used to study the electrolytes' crystalinity, thermgravimetric analysis(TGA) of the target prouducts were studied in the rang of 30^600°C by means of a TA(SDT Q600) system at a heating rate of 10°C -min"1. the surface morphology of such electrolytes was studied by the scanning electron microscopy using a JEOL (JSM-5601LV) instrument with gold-sputtered coated films. Analytical results show that the prepared gel polymer electrolytes have good chemical and physical characters and can be used as a better electrolyte material in Li-ion batteries.
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