PEO基Li1.5Al0.5Ge1.5（PO4）3固体复合电解质的制备

摘要

以聚环氧乙烷（PEO）为黏结剂，离子导电性的 Li1.5Al0.5Ge1.5(PO4)3（LAGP）为主相，乙腈为溶剂，按照EO/Li，摩尔比为13，变化LiN(CF3SO2)2（LiTFSI）中Li+与LAGP中Li+的比例，通过溶液浇注法制备得到LAGP-PEO(LiTFSI)固体复合电解质。用X射线衍射、扫描电镜（SEM）和电化学阻抗（EIS）等方法对固体复合电解质的形貌、结构和电导率进行表征。结果表明，LAGP 可与 PEO(LiTFSI)部分络合并均匀分散于PEO(LITFSI)内，整个体系内存有三个主体相，即PEO(LiTFSI)的复合相、LAGP晶相以及PEO与两种锂盐的过渡相。通过阻抗谱图发现，当质量比w(LAGP)∶w(PEO)=6∶4时，LAGP-PEO(LiTFSI)固体复合电解质具有最高的室温电导率，为2.68×10−5S/cm，在333 K时，达到1.86×10−4S/cm，接近LAGP的电导率水平。这说明固体复合电解质中加入LAGP即降低了PEO的结晶度，LAGP自身的电导率也有一定贡献。%PEO-based solid composite electrolyte with the fast ion conductor LAGP(Li1.5Al0.5Ge1.5(PO4)3) as a main ionic conductive component and PEO as the binder were prepared by the solution casting method with fixedn(EO)/n(Li)=13, but varying ratio of LiTFSI to LAGP. The structure and morphology of the solid composite electrolyte were characterized by X-ray diffraction(XRD) and scanning electron microscopy(SEM). The conductivity of LAGP-PEO(LiTFSI) electrolyte was analyzed by electrical impedance spectroscopy (EIS). The results show that LAGP is partially complexed with PEO(LiTFSI) and homogeneously distributed in PEO(LiTFSI). Three phases are present, a pure crystalline LAGP phase, amorphous PEO(LiTFSI) phase and a transition phase of the LAGP particles and amorphous PEO(LiTFSI). Withw(LAGP)∶w(PEO)=6∶4, the optimal ionic conductivity for LAGP-PEO(LiTFSI) solid composite electrolyte is 2.68×10−5S/cm at room temperature and 1.86×10−4S/cm at 373 K which is close to the LAGP. It means that the LAGP addition contributes to the improvements of ionic conductivity not only by prohibiting crystallization but also due to its own ionic conductivity.