分子间相互作用对复合固态聚合物电解质离子电导率的影响机制

Enhancement Mechanism of Intermolecular Interaction on Ionic Conductivity of Composite Solid Polymer Electrolytes

以聚氧化乙烯(PEO)为基体、埃洛石纳米管(HNTs)为填料,采用溶液浇铸法制备了系列聚氧化乙烯/高氯酸锂/埃洛石(PEO/LiClO4/HNTs)固态聚合物电解质。系统研究了HNTs经表面改性前后对PEO结晶性能、锂盐解离度及离子电导率的影响机制。透射电子显微镜和比表面积表征结果表明,HNTs经硫酸处理后(A-HNTs),可在保持纳米管形貌的基础上使其比表面积从33.15 m^(2)/g增加到104.73 m^(2)/g;X射线衍射和差示扫描量热法分析结果表明,HNTs经表面改性处理,可增加分子间的相互作用,进一步降低PEO的结晶度;光学显微镜结果证明,HNTs的加入可使PEO球晶尺寸减小,表面改性处理可进一步使PEO结晶细化;傅里叶变换红外光谱和离子电导率测试结果表明,通过对HNTs纳米管表面基团的控制,可以提高LiClO4解离程度,获得的电解质膜在40℃的离子电导率高达1.35×10^(-4) S/cm。

A series of polyethylene oxide/lithium perchlorate/halloysite(PEO/LiClO_(4)/HNTs) solid polymer electrolytes were prepared by solution casting method, with polyethylene oxide(PEO) as matrix and halloysite nanotubes(HNTs) as filler. Effects of HNTs before and after surface modification on the crystallization of PEO, the dissociation degree of lithium salt and the ionic conductivity of composite solid polymer electrolytes were systematically studied. TEM and specific surface area analysis results show that the specific surface area of HNTs modified by sulfuric acid(A-HNTs) is increased from 33.15 m^(2)/g to 104.73 m^(2)/g, without changing the nanotube morphology. XRD and differential scanning calorimetry results demonstrate that the surface modification of HNTs can further reduce the crystallization of PEO, through the molecular interaction enhancement among components. Optical microscopy images imply that the addition of HNTs could facilitate the heterogeneous nucleation of PEO and thus inhibit the growth of PEO spherulites. Moreover, the surface modification of HNTs might further refine the crystal size of PEO through molecular interaction. Furthermore, results of FT-IR and the ionic conductivity test show that the dissociation degree of LiClO_(4) could be effectively improved by controlling the surface groups of HNTs, and the ionic conductivity of the solid polymer electrolyte at 40 ℃ can reach up to 1.35×10^(-4) S/cm.