| In the lithium secondary battery, the lithium-sulfur battery is considered the most attractive of the battery system, its theoretical specific energy can reach 1200Wh/kg.At present, researches on lithium-sulfur battery electrolyte system used primarily for liquid electrolyte. However, the use of organic electrolyte Li/S battery is still exsiting issues such as security, lithium cathode graft and the soluble element sulfur loss .Studies have indicated that the introduction of polymer electrolyte to lithium-sulfur battery can have great application. This paper focus on problems such as low conductivity of ionic, poor electrode compatibility exist on lithium-sulfur secondary battery with polymer electrolyte, combined with Polysulfide compound which has the characteristics of excellent bonding, hydrophobic and solidify easily. Designed and synthesized a new type of content in order to improve the conductive properties of polymer electrolyte and the compatibility with the performance of sulfur electrode interface, and to get high expectations of the ionic conductivity, better processing film-forming performance and properties of the electrode polymer electrolyte compatible material.In this paper, according to two different synthetic routes ,we designed and synthesized a series of small molecules for branched-chain PEG, the main content of the polymer chain, named polyethylene glycol methacrylic acid ester-based compounds polysulfide (PS (MA-PEG ) and 1,3 - dichloro-2 - alcohol polyethylene glycol ether-based compounds polysulfide (PS (DCP-PEG)) respectively. This article has also obtained PS (DCP-PEG)/LiClO4/SiO2 composite polymer electrolyte by adulterating inorganic SiO2 to the synthesis of PS(DCP-PEG). To study the synthesis conditions of polymer, polymer structure, glass transition temperature, AC impedance spectra and conductivity properties by means of such as SEM, DTA, IR, TG, DSC, XRD, elemental analysis, and AC impedance. Through the analysis of these aspects, the paper discussed the performance of the composite polymer electrolyte conductivity enhancement mechanism. The main findings are as follows:(2) The AC impedance of PS(MAA-PEG)/LiClO4 system results showed that to contains on the sulfur polymer principal chain the PEG member stem grafting can obtain polymer that has certain ionic conductivity, and when taking PEG400, PEG600 as the branched chain ,the conductivity is the largest. At 25℃, the ionic conductivity of PS(MAA-PEG400)/LiClO4 was 8.39×10-6 S/cm, the ionic conductivity of PS(MAA-PEG600)/LiClO4 was 7.12×10-6 S/cm, the room temperature ionic conductivity of PS(MAA-PEG1000)/LiClO4 was 1.86×10-7 S/cm, when used PEG400 and PEG600 as branched-chain, the conductivity was the highest.(3) From the A.C. impedance spectra we can see that the conductivity of PS(DCP-PEG) /LiClO4 was higher than PEO/LiClO4; the results showed that ionic conductivity of PS(DCP-PEG400)/LiClO4 was 1.68×10-5 S/cm, the ionic conductivity of PS(DCP-PEG600)/LiClO4 was 1.10×10-5 S/cm.when the temperature is raised to 80℃, the ionic conductivity of both polymer electrolyte was 3.09×10-4 S/cm and 1.91×10-4 S/cm . the results showed that PS(DCP-PEG400)/LiClO4 had higher ionic conductivity than PS(DCP-PEG600)/LiClO4.(4)Two kinds of electrolyte PS(DCP-PEG400)/LiClO4/SiO2 and PS(DCP-PEG600)/LiClO4/SiO2 were prepared by a solution cast technique. The morphology, thermal performance, crystallinity and ionic conductivity of the CSPE were investigated by SEM, IR, DTA, TG, DSC, XRD and A.C impedance spectroscopy.DSC and XRD show that the crystallinity is observed to decrease greatly by addition of SiO2. The glass transition temperature (Tg) of composite polymer decrease by filling with inorganic particle SiO2. TG and DTA show that initial decomposition temperature of composite polymer is increased. The movement of polymer chain is restricted by SiO2 particle, thereby enhanceng the energy of polymer chain in the heating process, improving the thermal stability of polymer electrolyte when adding SiO2. the A.C. impedance spectra of composite polymer showed that the conductivity of composite polymer adding SiO2 was higher than PS(DCP-PEG) /LiClO4. Compared with the PS(DCP-PEG600)/LiClO 4/SiO2, the PS(DCP-PEG400)/LiClO4/SiO2 leads to higher enhancement in ionic conductivity When SiO2 concentration is at about 8wt%, the conductivity of composite polymer attains the maximum value. |
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