Composite polymer electrolytes using fumed silica fillers: synthesis, rheology and electrochemistry

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The goal of the synthesis research was to devise routes to PEG/fumed silica/lithium salt composites that can be processed and then photochemically cross-linked to form mechanically stable electrolytes. An essential feature of the system is that the ionic conductivity and the mechanical properties must be de-coupled from each other, i.e., cross-linking of the fumed silica matrix must not cause a significant deterioration of the conductivity of the composite. As shown in Figure 2, we prepared a range of surface-modified fumed silicas and investigated their ability to form mechanically stable composite electrolytes. The groups used to modify the surface properties of ... continued below

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14 pages

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Khan, Saad A.; Fedkiw, Peter S. & Baker, Gregory L. June 28, 1999.

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Description

The goal of the synthesis research was to devise routes to PEG/fumed silica/lithium salt composites that can be processed and then photochemically cross-linked to form mechanically stable electrolytes. An essential feature of the system is that the ionic conductivity and the mechanical properties must be de-coupled from each other, i.e., cross-linking of the fumed silica matrix must not cause a significant deterioration of the conductivity of the composite. As shown in Figure 2, we prepared a range of surface-modified fumed silicas and investigated their ability to form mechanically stable composite electrolytes. The groups used to modify the surface properties of the silica ranged from simple linear alkyls that render the silica hydrophobia to polyethers that promote compatibility with the electrolyte. From these materials we developed a cross-linkable system that satisfies the criteria of processibility and high-conductivity. The key material needed for the cross-linking reaction are silicas that bear surface-attached monomers. As shown schematically in Figure 3a, we prepared fumed silicas with a combination of surface groups, for example, an octyl chain with different coverages of tethered methacrylates. The length of the tether was varied, and we found that both C{sub 3} and C{sub 8} tethers gave useful composites. The functionalized silicas were combined with PEG-DM, AIBN or benzophenone (free radical initiators), LiClO{sub 4} or Li imide, and either methyl, butyl, or octyl, methacrylate to form stable clear gels. Upon irradiation with UV light, polymerization of both the tethered methacrylate and the added methacrylate took place, yielding a cross-linked rubbery composite material. Ionic conductivity measurements before and after cross-linking showed only a slight decrease (see Figure 9 later), thereby offering strong experimental evidence that the mechanical properties conferred by the silica matrix are de-coupled from the ionic conductivity of the PEG-DM matrix.

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14 pages

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OSTI as DE00761809

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  • Other Information: PBD: 28 Jun 1999

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  • Report No.: 94-ER-14495
  • Grant Number: FG05-94ER14495
  • DOI: 10.2172/761809 | External Link
  • Office of Scientific & Technical Information Report Number: 761809
  • Archival Resource Key: ark:/67531/metadc723629

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  • June 28, 1999

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  • Sept. 29, 2015, 5:31 a.m.

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  • March 11, 2016, 5:11 p.m.

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Khan, Saad A.; Fedkiw, Peter S. & Baker, Gregory L. Composite polymer electrolytes using fumed silica fillers: synthesis, rheology and electrochemistry, report, June 28, 1999; United States. (digital.library.unt.edu/ark:/67531/metadc723629/: accessed August 19, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.