Research On Gel And Solid Polymer Electrolyte Membranes In Lithium Battery

Lithium-ion batteries not only avoided the leakage faults but also possessed many merits such as incombustibility,low reactivity with electrode,good flexibility,impact resistance,easy mold-processing when compared with liquid electrolyte,which extensively used in electric vehicles?EV?,hybrid electric vehicles?HEV?,communications and many other fields.This paper prepared two kinds of lithium ion polymer electrolyte membranes:N-methyl-N-butylpiperidinium bis?trifluoro me-thanesulfonimide?ionic liquid(Pp₁₄TFSI IL)/Polyvinylidenedifluoride?PVd F?/Polyvinyl Butyral?PVB?/?IL-GPE?,montmorillonite?MMT?/Polyvinylidenedifluoride?PVd F?/Polyvi nyl Butyral?PVB??MMT-SPE?by solution casting method through the simple blending.The optimum scheme of membranes were employed through the study on the relation between different substrate ratio and conductivity as well as the relation between different IL content and conductivity,MMT content and conductivity,which provided theory basis for the further research.Scanning electron microscopy?SEM?,atomic force microscope?AFM?,thermogravimetric analysis?TG?,mechanical testing methods were utilized to study the the physical properties of the polymer membrane.Linear scanning voltage?LSV?,cyclic voltammograms?CV?,AC impedance electrochemical testing and charge and discharge test were applied to explore the electrochemical properties of electrolyte membrane.The result showed that the electrochemical stability window in IL-GPE with 45%?0.5 g?ionic liquid was 4.6 V,a lithium ions transference number of 0.55 at room temperature was obtained,the absence of liquid electrolyte greatly improved the safety of lithium ion batteries and cathode delivered a discharge capacity of 130 m Ah/g with a coulombic efficiency over 97%after 30 cycles at room temperature.The electrolyte showed an electrochemical stability window of 5.0 V and lithium ions transference number of 0.46 at room temperature when the MMT addition was 4%of PVd F matrix.The Li/MMT-SPE/Li Fe PO₄ cells showed pretty high specific discharge capacity above 123 m Ah/g coupled with a coulombic efficiency of 98.1%after 30 cycles.So we claimed that both Pp₁₄TFSI IL/PVd F/PVB and MMT/PVd F/PVB were good candidates for the application of lithium battrty.