Al稳定立方相Li7La3Zr2O12固态电解质的场助烧结制备

摘要

石榴石型结构的固态电解质Li7La3Zr2O12(LLZO)因其良好的力学性能、化学稳定性、高离子电导率等特点有着广阔的应用前景.Li7La3Zr2O12(LLZO)具有四方相和立方相两相,其中立方相比四方相有更高的离子电导率(~10-3S/ cm).本文利用场助烧结的制备方法,通过在Li7La3Zr2O12(LLZO)体系中掺杂Al3+来稳定立方相的生成,制备了高离子电导、高致密的立方相Li7La3Zr2O12(LLZO)电解质,探究了Al3+在立方相LLZO中的存在形式.实验采用FESEM、XRD、NMR和交流阻抗等方法研究了固体电解质的表面形貌、物相、Al3+的存在形式及离子电导率.实验结果表明,在1150 ℃烧结温度下,Al2O3含量为1.5wt.%时,LLZO在室温下具有最高的离子电导率5.7×10-4S/cm,Al位于LLZO晶粒中取代四面体中的Li,且相对密度约为99.8%.%All solid state lithium ion battery with high voltage, high energy density, and good safety performance is one candidate to replace the currently-used liquid electrolyte in the future in a wide range of consumer electronics, electric vehicles and grid energy storagesystems. In recent years, a novel class of inorganic ceramic solid electrolyte with garnet structure Li7La3Zr2O12, known as LLZO, has been developed. LLZO has two phases: cubic phase and tetragonal phase. The Li-ion conductivity for cubic phase which is available for application is ~ 10-3S/cm, compared to ~ 10-6S/cm for the tetragonal phase. To obtain the cubic phase, Al is necessary for the stability of the cubic phase calcined at high temperature by FAST. The morphology, ionic conductivity and conductivity of the existence form of Al3+in the cubic LLZO were studied using FESEM, XRD, NMR and electrical impedance spectroscopy, respectively. The results show that the sample sintered at 1150 ℃ has a maximum relative density value of 99.8% and the highest ionic conductivity value is about 5.7×10-4S/cm. and the NMR results show that the Al cation is located in the tetrahedrally coordinated 24 d site in cubic LLZO.