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

Investigations of microstructure and ionic conductivity for (PEO)8-ZnO-LiClO4 polymer nanocomposite electrolytes

The effects of nanosized ZnO on the microstructure, the free volume and the ionic conductivity of poly ethylene oxide (PEO) nanocomposite electrolytes (PEO)₈-ZnO-LiClO₄ are systematically studied by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and positron annihilation lifetime spectroscopy (PALS), respectively. The experimental results show that the presence of the nanosized ZnO brings about a reduction in the crystallinity of the PEO phase and a very marked increase in ionic conductivity. PALS discrete analysis shows that the free volume size, the free volume concentration and the relative free volume fraction significantly increase with the increase of nano-ZnO. Specially, it is the first time to observe the occurrence of peaks of the free volume distribution split after nano-ZnO has been filled, which indicates that the ZnO added into (PEO)₈-LiClO₄ has an important effect on the microstructure for nanocomposites due to the interaction between the nano-ZnO and matrix. A direct correlation between the free volume fraction and the ionic conductivity is observed, and the ionic conductivity mechanism is discussed.