Study On The Preparation And Characterization Of Gel Polymer Electrolytes For Lithium Ion Secondary Batteries

Gel polymer lithium-ion battery (GPLB) is a novel secondary rechargeable system generating on the basis of liquid lithium-ion battery. GPLBs not only have the excellent performance of liquid lithium batteries, but also can resolve the possible problems of leakage and blast owing to no free liquid electrolyte in GPLB. It is also very convenient to design the shape at will. With the increase of power sources, the research of gel polymer electrolyte(GPE) have attracted more and more attentions. At present, the common preparation methods for PGE are Bellcore and solution-casting technology, and it is physically cross-linked for the PGE produced by Bellcore and solution-casting technology. In this dissertation, the preparation of chemical crosslink gelled polymer electrolyte membrane by thermal polymerization was investigated following two methods.The GPE membranes of better stability compared with physically cross-linked GPE membranes was desirably prepared.Firstly, gel polymer blend electrolyte films of polyethylene glycol diacrylate (PEGDA)/poly (vinylidene fluoride)-hexafluoropropene and Li⁺ electrolytes were prepared by thermal curing of using benzoyl peroxide as a catalyst. FTIR, XRD, TGA, SEM, tensile test, AC impedance were used to investigate the microstructure and electrochemical characteristics of the chemically cross-linked GPE membranes. It was also investigated that the effect of chemical crosslink on the electrochemical characteristics. The blend GPE membranes have the highest Li⁺ ionic conductivity in 2.0xl0^-3S/cmat25℃.Secondly, in order to improve the preparation process of gelled polymer electrolyte membranes, the porous gelled polymer electrolyte membranes was prepared by thermal curing the mixed solution of PEGDA/liquid electrolyte in PVDF-HFP porous membranes (via the immersion precipitation method). The influence of chemical crosslink on the heat stability, electrolytes capability, mechanical properties and the time stability of ion conduction of porous gelled polymer electrolyte membranes were studied. The relationship between crosslink ,ratios of PEGD A/electrolytes and the ion conduction of porous GPE membranes were discussed. The ionic conductivity of these porous GPE membranes The ionic conductivity could reach 2.245x10"3S/cm at 25 °C.