聚合物纳米复合电解质(PEO)8-ZnO-LiClO4微结构及电导率研究

以聚氧化乙烯(PEO)为基质,成功制备出纳米ZnO掺杂的(PEO)₈-ZnO-LiClO₄离子导电聚合物电解质,并利用多种实验技术,包括扫描电子显微镜、X射线衍射(XRD)、傅里叶变换红外光谱和正电子湮没寿命谱(PALS),系统地研究了纳米ZnO与基质间相互作用及其对聚合物链段运动、纳米尺度自由体积、离子输运和复合电解质电导率的影响.实验结果发现,纳米ZnO的掺杂使聚合物电解质的离子电导率得到了大幅度提高,当ZnO与PEO质量比为6%时达到最大,(PEO)₈-ZnO-LiClO₄的电导率为1.82×10^-4 S ·cm^-1,比(PEO)₈-LiClO₄的电导率(6.58×10^-5 S ·cm^-1)提高了大约一个数量级.XRD结果显示,纳米ZnO的加入降低了PEO的结晶性,增加了锂离子传输的非晶相,从而提高了电导率.离散PALS测量结果表明,随着纳米ZnO的加入,复合电解质的自由体积、浓度和相对自由体积分数f_r均增加.连续PALS分析揭示了自由体积的分布由一个峰劈裂成两个峰,表明纳米ZnO的掺杂对聚合物的微结构有很大影响.基于实验测量的f_r和离子电导率,研究了离子导电机理.研究发现, f_r与电导率之间存在一个直接关系,即f_r越大,越有利于锂离子的传输,导致电导率越大.这个结果支持聚合物电解质导电的自由体积理论. 关键词： 正电子湮没寿命谱 聚合物纳米复合电解质 离子电导率 自由体积     

Investigation of the free volume and ionic conducting mechanism of poly（ethylene oxide）-LiClO_4 polymeric electrolyte by positron annihilating lifetime spectroscopy

The positron annihilation lifetime and ionic conductivity are each measured as a function of organophilic rectorite（OREC） content and temperature in a range from 160 K to 300 K.According to the variation of ortho-positronium（o-Ps） lifetime with temperature,the glassy transition temperature is determined.The continuous maximum entropy lifetime（MELT） analysis clearly shows that the OREC and temperature have important effects on o-Ps lifetime and free volume distribution.The experimental results show that the temperature dependence of ionic conductivity obeys the Vogel-Tammann-Fulcher（VTF） and Williams-Landel-Ferry（WLF） equations,implying a free-volume transport mechanism.A linear least-squares procedure is used to evaluate the apparent activation energy related to the ionic transport in the VTF equation and several important parameters in the WLF equation.It is worthwhile to notice that a direct linear relationship between the ionic conductivity and free volume fraction is established using the WLF equation based on the free volume theory for nanocomposite electrolyte,which indicates that the segmental chain migration and ionic migration and diffusion could be explained by the free volume theory.     

Investigation of the free volume and ionic conducting mechanism of poly（ethylene oxide）-LiClO₄ polymeric electrolyte by positron annihilating lifetime spectroscopy

The positron annihilation lifetime and ionic conductivity are each measured as a function of organophilic rectorite(OREC) content and temperature in a range from 160 K to 300 K.According to the variation of ortho-positronium(o-Ps) lifetime with temperature,the glassy transition temperature is determined.The continuous maximum entropy lifetime(MELT) analysis clearly shows that the OREC and temperature have important effects on o-Ps lifetime and free volume distribution.The experimental results show that the temperature dependence of ionic conductivity obeys the Vogel-Tammann-Fulcher(VTF) and Williams-Landel-Ferry(WLF) equations,implying a free-volume transport mechanism.A linear least-squares procedure is used to evaluate the apparent activation energy related to the ionic transport in the VTF equation and several important parameters in the WLF equation.It is worthwhile to notice that a direct linear relationship between the ionic conductivity and free volume fraction is established using the WLF equation based on the free volume theory for nanocomposite electrolyte,which indicates that the segmental chain migration and ionic migration and diffusion could be explained by the free volume theory.