Effect of Grain Size on the Ionic Conductivity of a Block Copolymer Electrolyte

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• 作者：Mahati Chintapalli ; X. Chelsea Chen ; Jacob L. Thelen ; Alexander A. Teran ; Xin Wang ; Bruce A. Garetz ; Nitash P. Balsara
• 刊名：Macromolecules
• 出版年：2014
• 出版时间：August 12, 2014
• 年：2014
• 卷：47
• 期：15
• 页码：5424-5431
• 全文大小：463K
• ISSN：1520-5835

文摘

A systematic study of the dependence of ionic conductivity on the grain size of a lamellar block copolymer electrolyte was performed. A freeze-dried mixture of poly(styrene)-block-poly(ethylene oxide) and lithium bis(trifluoromethylsulfonyl)imide salt was heated in steps from 29 to 116 掳C and then cooled back to 29 掳C with an annealing time ranging from 30 to 60 min at each temperature. Grain structure and ionic conductivity during these steps were quantified by in situ small-angle X-ray scattering and ac impedance spectroscopy, respectively. Conductivity depends both on grain structure and temperature. A normalization scheme to decouple the dependence of conductivity on temperature and grain structure is described. Ionic conductivity at a given temperature was found to decrease by a factor of 5.2 卤 0.9 as the SAXS measure of grain size increased from 13 to 88 nm. The fact that in the system studied, large, well-formed lamellar grains are less conducting than poorly defined, small grains suggests a new approach for optimizing the transport properties of block copolymer electrolytes. Further work is necessary to confirm the generality of this finding.