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- Gavelin, Patrik, et al.
(author)
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Amphiphilic polymer gel electrolytes. 3. Influence of the ionophobic-ionophilic balance on the ion conductive properties
- 2001
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In: Electrochimica Acta. - 0013-4686. ; 46:10-11, s. 1439-1446
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Journal article (peer-reviewed)abstract
- Gel electrolytes based on amphiphilic copolymethacrylates containing ethylene oxide (EO)(n) side chains as ionophilic units and fluorocarbon (CF,), side chains as ionophobic units showed a substantial increase in ion conductivity, as compared to corresponding gels based on homopolymers of (EO),, methacrylate. The highest ion conductivity was found for a gel based on a copolymer composed of 24 wt% of (EO)(9) methacrylate and 76 wt% of fluorocarbon methacrylate. This gel contained 70 wt% of 1 M LIPF6 gamma -butyrolactone, and had an ion conductivity of 4.0 mS/cm at 20 degreesC, and 1.0 mS/cm at - 20 degreesC. It was found that gels based on fluorocarbon-containing copolymers having (EO), side chains had higher ion conductivities than gels based on copolymers containing (EO), side chains. The study showed that it is important to control the ionophobic-ionophilic balance of the amphiphilic copolymer in order to achieve high ion conductivities in the gel electrolyte. It is very likely that the ionophobic side chains of the copolymer associated to form microdomains in the electrolyte. It is also likely that longer EO chains increased the stability of these microdomains in the electrolyte. However, strong lithium ion coordination to EO chains above a critical chain length may have suppressed the ion conductivity of the gels.
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| 2. |
- Gavelin, Patrik, et al.
(author)
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Amphiphilic solid polymer electrolytes
- 2002
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In: Solid State Ionics. - 1872-7689 .- 0167-2738. ; 147:3-4, s. 325-332
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Conference paper (peer-reviewed)abstract
- Amphiphilic graft copolymers consisting of methacrylate backbones carrying approximately 48 wt.% of ethylene oxide [(EO)(9) or (EO)(23)] side chains as ionophilic groups and fluorocarbon or hydrocarbon side chains as ionophobic groups were prepared. Solid polymer electrolytes based on the copolymers and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) were characterized by DSC and the impedance spectroscopy. A maximum ion conductivity of 8 x 10(-5) S cm(-1) at 60 degreesC was found for a polymer electrolyte based on a copolymer having hydrocarbon side chains and (EO)(23) side chains, despite an EO content of only 50 wt.%. No (EO)(n) side chain crystallinity in the electrolytes was detected by calorimetry. The hydrocarbon side chains, on the other hand, were found to form a crystalline phase in the electrolytes. The melting of this phase was not reflected in the shape of the Arrhenius conductivity plot. This indicated that the segmental mobility in the ion conducting phase did not decrease as a result of the presence of the crystalline hydrocarbon phase.
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