Study On Preparation Process And Properties Of PEO-based Polymer Electrolytes

Nowadays,high capacity lithium ion batteries have been widely used in daily life as energy storage devices.Solid-state polymer lithium ion batteries have drawn a great attention due to their advantages of no electrolytes leakage risk,strong plasticity and high volume utilization ratio.Polyethylene oxide（PEO）has been a popular topic in the field of electrolytes.However,the movement of lithium ions is limited due to the crystalline state of PEO,which makes the conductivity not suitable for the application requirements in room temperature.In order to improve the conductivity of the electrolyte and optimize its mechanical properties,the PEO and PEO/PLA blend polymer electrolytes were fabricated and then characterized with the composites containing 1.96wt.%and 3.62wt.%of main chain liquid crystal ionomer intercalated montmorillonites（LLCT and HLCT）using automatic scraping method.To the best of our knowledge,the study has not be reported previously.The following is the main research work:In the PEO electrolytes system,the optimum preparation process for orthogonal experiment was the concentration of PEO solution of 4×10^-5mol/L,the stirring time of 3h,the film is removed after drying for 3h,and the scraping speed is 20mm/s.As the content of LLCT increased,the crystallinity of PEO decreased initially and then increased.In contrast,the crystallinity of the HLCT system increased initially and then decreased.The maximum conductivity of the system was 3.30×10^-5S/cm with 1wt.%LLCT,which was increased by161.90%compare with the sample without LCT adding.However,the conductivity of the HLCT/PEO system decreased as LCT content increased.After LCT was added,both the stress and strain of the electrolytes increased,and there was no breakage as the maximum strain reached 800%with 1wt.%LLCT.In the PLA/PEO（30/70 wt./wt.）composite electrolytes system,the orthogonal test results showed that the best preparation process for the electrolyte is to dissolve the PEO and PLA for12h,under 700r/min for 1.5h,and then remove the film after drying for 3h.LLCT suppressed the crystallinity of PEO phase and improved the crystallinity of PLA,while the addition of HLCT increased the crystallinity of both PEO and PLA.The maximum conductivity of the electrolytes with 0.5wt.%LLCT was 1.39×10^-5S/cm,and the conductivity of the system with LLCT was higher than that of the system with HLCT.As the content of LCT increased,there was no significant change of the maximum stress,whereas the maximum strain showed an increasing trend.In the PEO/PLA（50/50wt./wt.）composite electrolytes system,the best preparation process of the electrolyte was to dissolve the PEO and PLA for 18h,magnetically stir the blended electrolytes at 700r/min for 1.5h,and then remove the film after drying for 3h.As the content of LLCT reached 1%,the crystallinity of PEO slightly decreased,and the overall crystallinity of the system was decreased.The addition of HLCT increased the crystallinity of both PEO and PLA.The conductivity of both systems reached the highest with 1wt.%LCT.The conductivity of the LLCT system increased from 6.09×10^-6S/cm to 9.27×10^-5S/cm,and the conductivity reached 2.56×10^-5S/cm when HLCT were added.The stress and the strain of both systems reached the maximum with 2wt.%LCT.