二锂
离子电导率
玻璃化转变
电解质
离子键合
无机化学
锂(药物)
化学
电导率
酰亚胺
离子
聚合物
高分子化学
材料科学
物理化学
有机化学
医学
电极
脱质子化
内分泌学
作者
Olt E. Geiculescu,Rama Rajagopal,Emilia Cerna Mladin,Stephen E. Creager,Darryl D. DesMarteau
出处
期刊:ChemPlusChem
[Institute of Organic Chemistry & Biochemistry, Academy of Sciences of the Czech Republic]
日期:2008-01-01
卷期号:73 (12): 1777-1798
被引量:1
摘要
The present work consists of a series of studies with regard to the structure and charge transport in solid polymer electrolytes (SPE) prepared using various new bis(trifluoromethanesulfonyl)imide (TFSI)-based dianionic dilithium salts in crosslinked low-molecular-weight poly(ethylene glycol). Some of the thermal properties (glass transition temperature, differential molar heat capacity) and ionic conductivities were determined for both diluted (EO/Li = 30:1) and concentrated (EO/Li = 10:1) SPEs. Trends in ionic conductivity of the new SPEs with respect to anion structure revealed that while for the dilute electrolytes ionic conductivity is generally rising with increased length of the perfluoroalkylene linking group in the dianions, for the concentrated electrolytes the trend is reversed with respect to dianion length. This behavior could be the result of a combination of two factors: on one hand a decrease in dianion basicity that results in diminished ion pairing and an enhancement in the number of charge carriers with increasing fluorine anion content, thereby increasing ionic conductivity while on the other hand the increasing anion size and concentration produce an increase in the friction/entanglements of the polymeric segments which lowers even more the reduced segmental motion of the crosslinked polymer and decrease the dianion contribution to the overall ionic conductivity. DFT modeling of the same TFSI-based dianionic dilithium salts reveals that the reason for the trend observed is due to the variation in ion dissociation enthalpy, derived from minimum-energy structures, with respect to perfluoroalkylene chain length.
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