Preparation And Property Investigation Of PEO-Based Solid Polymer Electrolytes

All-solid-state Li metal batteries,with higher energy density and more reliable security than traditional Li ion batteries employing liquid electrolytes,are recognized as the most promising candidate for energy storage.As the key materials for solid state batteries,solid state electrolytes can be generally divided into solid inorganic electrolytes(SIEs)and solid polymer electrolytes(SPEs)depending on the composition.Among them,SPEs have superior flexibility and can enable tight contact with electrodes,which is benefit for interfacial ion transport.Besides,SPEs have isostatic properties at each aspects,and are low cost and easy manufacturing,which is the colsest choice for market-oriented scale application.However,SPEs possess some drawbacks,such as low ionic conductivity,narrow electrochemical window,inferior ion selectivity and so on.Besides,lithium dendrites and interfacial reactions are also emerging when matching with Li anodes.This project takes polyethylene oxide(PEO)as the research object,modifies the PEO-based SPEs through inorganic fillers doping and investigates the influence of doping to the properties of SPEs.In addition,from the aspect of macromolecule,we design and synthesis a new kind of PEO-derived electrolyte,explore its electrochemical performance and compatibility with Li.The main research contents of this article are summarized as follow:(1)We prepared Ag-doping MnO2(AMO)by a hydrothermal method.Images of electron microscope demonstrate the product is sea urchin-like sphere consisting of nanowires.The total scale of the product is around 4 ?m and the diameter of the nano wires are nearing 10 nm.XPS shows there are plenty of oxygen vacancy on the surface.Then,take AMO as filler to blend with PEO and prepare composite polymer electrolytes through casting method.The crystal degree of PEO drop down dramatically,in the meantime the ionic conductivity and ion transport number get improved obviously.With 10%AMO adding mass(PEO-10AMO),the sample has an ionic conductivity of 1.2×10-5 S cm-1 and transference number of 0.36 at 25?Infrared spectra shows there are interactions between oxygen vacancy of AMO and Li salt,which can help the the dissolution of Li salt and immobilization of anion.PEO-10AMO demonstrates excellent compatibility with Li.The Li symmetric cell can steadily run over 1400 h without short circuit,while the polarization voltage grows from 0.08 V to 0.15 V.Besides,the doping of AMO can also improve the cycling performance and rate performance of full cells.(2)Using Poly(ethylene glycol)diacrylate,Poly(ethylene glycol)methyl ether acrylate and Zinc methacrylate as raw material,a novel Zn2+containing poly-ionic SPEs(SPE-xZn,x=mznMA/mmatrx)was synthesized by free radical polymerization,and the influence of ZnMA usage on the electrochemical performance of SPE-xZn was also investigated.The results demonstrate that the usage of ZnMA will impair the ionic conductivity but slightly improve transference number for SPE-xZn.For example,ionic conductivity for SPE-OZn and SPE-10Zn are 1.88 × 10-4 S cm-1 and 8.13 × 10-5 S cm-1 at 60?,respectively.And the transference number for SPE-OZn and SPE-10Zn are 0.23 and 0.26,respectively.The usage of ZnMA can improve the compatibility between SPE-xZn and Li.The Li symmetric cell assembled with SPE-5Zn displays stable cycling at 0.2 mA cm-1 with a low initial polarization voltage of 0.11 V.The cycled Li electrode presents a relative smooth surface without obvious Li dendrites.XPS suggests that Li-Zn alloy is formed on its surface and the product of side reaction(LiF)is less than that of the control group.Full cell equipped with SPE-5Zn demonstrates impressive cycling stability,which could realize a capacity retention of 87.3%at 0.5 C for 800 cycles with an average coulombic efficiency of 99.9%.