Preparation And Properties Of Optically Active Spiral Polyurethane Solid Electrolytes

With the rapid development of microelectronics and energy industry,the requirements for lithium-ion battery become higher and higher.In recent years,more and more researchers focus on the developing of all solid state polymer electrolytes in order to design and produce higher performance lithium-ion batteries.Compared with the traditional liquid electrolytes,solid polymer electrolytes are easy processing and have no leakage,good thermal stability and high energy density.The introduction of polyurethanes with novel optically active and helical structure into the electrolyte is significant for the developing of new and high performance electrolyte matrix materialsThe manuscript mainly studies on the following aspects:1.Optically active polyurethanes with different enantiomeric excess of tyrosine derived monomers were prepared.The structures of the polymers were characterized by FT-IR,UV-Vis and NMR,and the degree of hydrogen bondings was also investigated.Furthermore,the crystallinity and secondary structure of the polymers were analyzed by XRD,UV-Vis and CD.It was proved that the polyurethane based on L-tyrosine had regular helical structure,whereas the racemic polyurethane derived from DL-tyrosine did not have any optical activity,and the macromolecular chains exhibited random coiled state;2.The effect of types and contents of different lithium salts and polyurethanes with different side chains on the ionic conductivity of the solid state electrolytes was studied by means of electrochemical impedance spectroscopy?EIS?.Moreover,the impact of different enantiomeric excess on the optical activity of the polyurethane and the corresponding electrochemical impedance spectroscopy?EIS?were also studied.It demonstrated that the ordered helical secondary structure improved the ionic conductivity of electrolyte;3.The modification of the optically active helical polyurethane based solid electrolyte was conducted.The electrolyte film prepared by blending of helical polyurethane with poly?lithium methacrylate?exhibited high ionic conductivity of 5.78×10^-5 S/cm.Thermogravimetric analysis of the composite electrolyte showed that this solid electrolyte possessed good thermal stability with onset decomposition temperature of 200?.At the same time,a single ionic conductor of solid electrolyte based on helical polyurethane was synthesized and investigated.The ion conductivity of this polymer electrolyte attained 6.12×10^-6 S/cm by mixing with ionic liquid at room temperature.