| Benefited from the electric vehicle'fast development, the power lithium ion battery will has a fast-growing market in the future. The liquid lithium ion battery was studied early time, cost low, and dominated the currently 90% finished lithium battery market. The polymer lithium ion battery has high specific energy density, can realize the battery'thin shape optimization, and is easier to mass industrial production. Thus, it will be able to carry more long life ability, reduce the weight and volume of the battery, it is expected to be a important role in pure electric vehicle age, and it is one of the future development direction.In this thesis,a series of PUA were synthesized by bulk polymerization,using isophorone diisocyanate(IPDI),different molar mass poly(ethylene glycol)(PEG) and hydroxyethyl methacrylate(HEMA) as the raw materials.They were used as the bases of gel polymer electrolytes(GPES).The acetone—di-n-Butylamine titration and FTIR were used to detect reaction degree. The effects of synthetic route, reaction temperature, the molar ratio of raw materials for the synthesis of process conditions of PUA were studied. The result showed the synthesis of PUA prepolymer included two steps. The suitable synthetic conditions was the reaction temperature was 60℃~ 75℃, the ratio of n (IPDI) :n (PEG) was 1:2,the reaction time was 2h in the first step,and the reaction temperature was 55℃~ 65℃, the ratio of n(PEG) :n(HEMA) was 1:1.04, the reaction time was 2.5 h in the second step. Poly (ethylene glycol) in PUA synthesis determines its structure and main performance, in certain molecular weight, the resin viscosity of PUA decreased with the increasing of polyols molecular weight.In a vacuum oven, PUA and a certain proportion of initiator 1173 were blended with the liquid electrolyte with a electric mechanical agitator, making the polymer and the lithium salt, the plasticizer form an uniform phase.The solution is then put in glass mold, forming thin layer with the same thickness.It was completely cured by 365nm hand-held lamp UV radiation curing light to get a cured polymer electrolyte film.The greater the viscosity of PUA, the poorer the compatibility with liquid electrolyte.It caused a decrease of curing speed and mechanical strength of gel film, adhesion,the flexibility also dropped,and the curing advantage of PUA reduced.Alternating current impedance(ac) impedance method was used to determine electrical conductivity of gel electrolyte with different liquid electrolyte levels, and the results showed that the electrical conductivity increased with the increasing of the content of liquid electrolyte in the first, when the content to a certain extent, the conductivity was almost unchanged, the room temperature conductivity reached 3.0 x 10-3S/cm.Its chemical and physical properties were characterized by curing efficiency,flexible property,FTIR spectroscopy,differential scanning caborimetry(DSC),scanning electron microscopy(SEM).The result showed the structure of the polymer had a great effect on the structure and flexibility of gel electrolyte membrane.The flexibility of the electrolyte membrane does not change significantly with the increasing of the content of liquid electrolyte at first,and the flexible property became significantly worse when its content to a certain extent.Polymer electrolyte occurred thermo-gravimetric behavior in around 260℃,and this thermo-gravimetric behavior even due to polymer,it also reached the thermal stability of lithium ion battery application requirements. |
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