PVA-膨润土-KOH-H2O复合碱性聚合物电解质的制备与表征

以聚乙烯醇(PVA)与膨润土(bentonite)和氢氧化钾为原料, 采用溶液浇铸法制备了PVA-膨润土-KOH-H2O复合碱性聚合物电解质膜. 运用X衍射(XRD)、扫描电镜(SEM)和循环伏安(CV)等技术对复合膜进行了表征, 分析了膨润土对聚合物膜电导率的影响. 结果表明, 膨润土对电解质的导电性能具有双重作用: 一方面膨润土本身会阻塞PVA内部结构中的部分离子通道, 导致复合电解质的电导率降低; 另一方面, 膨润土有助于体系中KOH含量的增加, 同时PVA-膨润土相界面高导电性缺陷层的形成有助于体系电导率的提高. 当体系水的质量分数较低时, 复合电解质体系电导率存在极大值; 当w(H2O)为65%时, 则观察到电导率的线性增加趋势; 电解质最高室温电导率达0.110 S·cm-1. XRD图谱显示适当配比的复合膜中PVA呈无定形态; SEM结果证实了适当配比的复合膜中存在大量微米级孔径的微孔通道. 循环伏安曲线表明PVA-膨润土-KOH-H2O碱性聚合物电解质膜有约2.0 V的较宽电化学稳定窗口.

Preparation and Characterization of the Composite Alkaline Polymer Electrolyte Based on PVA-Bentonite-KOH-H2O

A series of composite alkaline polymer electrolyte membranes composed of poly(vinyl alcohol) (PVA), potassiumhydroxide (KOH), bentonite, and water were prepared by a solution casting method. The composite alkaline polymer electrolytes of PVA-bentonite-KOH-H2O were characterized by XRD, SEM, and CV technologies. The influence of bentonite on electrical conductivity of the composite membrane was studied. The results indicated that the bentonite had dual effects on the conductivity of the composite membrane; on one hand, it could decrease the conductivity of composite membrane by blocking the ion transfer tunnel in the PVA polymer structure, on the other hand, it improved the conductivity by increasing the KOH content in the composite electrolyte and forming a highly conductive defective layer on PVA-bentonite phase interface. However, in the system, when the water mass fraction was relative lower, the conductivity of the composite electrolyte system had a maximun value, while at a more higher water content w(H2O)=65%, the conductivity of the systemincreased linearly. The highest electrical conductivity reached 0.110 S·cm-1 at roomtemperature. XRD patterns revealed the amorphous structure of PVA in the composite membrane with appropriate mass ratio; SEM test confirmed that the bentonite-blending composite membrane contained a lot of micro-tunnels; cyclic voltammetry measurement demonstrated that composite alkaline polymer electrolyte membrane had a wide electrochemical stable window (about 2.0 V).