聚氧化乙烯基聚合物电解质中离子缔合与结晶状态的傅立叶变换红外光谱(FTIR)研究

FTIR Characterization of Ion Association and Phase Composition in PEO-based Polymer Electrolytes

通过FTIR光谱技术对P(EO)nLiX[X=N(SO2CF3)2,SCN,ClO4](n=4～60)聚合物电解质的离子缔合行为进行了研究,结果表明在PEO-LiSCN体系中缔合现象较为严重.在高浓度时LiSCN主要以离子对、离子簇以及二聚体形式存在,自由离子含量较少.而对于LiTFSI和LiClO4体系,则以自由离子形式为主.随着锂盐的加入,由于其阴离子的增塑作用使聚氧化乙烯(PEO)中的晶相成分逐渐向无定形相转化.当锂盐含量增加到一定程度,体系中会有不同晶相复合物的形成.

FTIR spectra of P（EO）nLiX [X=N（SO2CF3）2, SCN, ClO4] polymer electrolytes have been obtained for ethylene oxide/Li ratios from 60 ; 1 to 4 ; 1. It was shown that ion association in the PEO-LiSCN system is more serious than in the other two systems. At a high LiSCN concentration, contact ion pairs, triple ions and dimers are main ion species in the polymer electrolytes. However, free ions are main ion species in PEO-LiTFSI and PEO-LiClO4 systems. When Li salt was added into PEO, a plastizing role of Li salt anions can lead to transformation of a crystalline phase of PEO into an amorphous phase. When Li salt content exceeds a certain value, some kinds of crystalline complexes will be formed in PEO-LiX systems.