Electrolytes films, preparation

Microsohd state batteries in the form of thin films partly avoid the irrterfaee eorrtact difficirlty and can be ttsed as devices in microelectronics. Recently, eonsiderable atterrtion has been focitsed on the preparation of solid state lithium batteries using sohd polymer electrolytes which are made from polymer complexes formed by hthirrm salts arrd polymer ethers. Ultrathin-film solid state lithirrm batteries have been fabricated using a thin solid polymer electrolyte film prepared by complexation of a plasma polymer and hthirrm perchlorate. ... 

A series of studies were reported that used PMMA as the host polymer. " In one study, using polymer electrolyte films prepared from PMMA and LiBF4 with different concentrations of plasticizer (dibutyl phthalate, DBP), the conductivity observed was in the range 4.5 x 10 to... 

Thin-film solid electrolytes in the range of lpm have the advantage that the material which is inactive for energy storage is minimized and the resistance of the solid electrolyte film is drastically decreased for geometrical reasons. This allows the application of a large variety of solid electrolytes which exhibit quite poor ionic conductivity but high thermodynamic stability. The most important thin-film preparation methods for solid electrolytes are briefly summarized below. 

Perhaps more important than cost is the solution to the crucial problem of interfacial contacts that always plagues homogeneous GPE films prepared from traditional approaches. Since both cathode and anode composite materials are coated on their substrates with the same PVdF—HEP copolymer as the binder, the in situ gellification following the electrolyte activation effectively fuses the three cell components into an integrated multilayer wafer without physical boundaries, so that the interfaces between anode and electrolyte or cathode and electrolyte are well extended into the porous structures of these electrodes, with close similarity to the interfaces that a liquid electrolyte would access. 

Another type of Chi interfacial layer employed on a metal electrode was a film consisting of ordered molecules. Villar (79) studied short circuit cathodic photocurrents at multilayers of Chi a and b built up on semi-transparent platinum electrodes in an electrolyte consisting of 96% glycerol and 4% KCl-saturated aqueous solution. Photocurrent quantum efficiencies of multilayers and of amorphous films prepared by solvent evaporation were compared. The highest efficiency (about 10 electrons/ absorbed photon, calculated from the paper) was obtained with Chi a multilayers, and the amorphous films of Chi a proved to be less efficient than Chi b multilayers. 

Hibino, T., Hashimoto, A., Suzuki, M., Yano, M., Yoshida, S., and Sano, M. A Solid Oxide Fuel Cell with a Novel Geometry that Eliminates the Need for Preparing a Thin Electrolyte Film, Journal of the Electrochem. Soc., 149, A195 (2002). 

To conclude with the primary electrode characteristics, we describe briefly the DLC electrodes. The data are scarce and partly contradictory, probably due to the differences in film preparation methods. According to Howe [60], even films as thin as 50 nm are quite stable against corrosion. However, in later works [61, 62] such thin films turned permeable for electrolytes. The penetration of the electrolyte to a substrate metal resulted in its corrosion and, ultimately, in film peeling. Thicker films (0.1 to 1 pm) were less subjected to damage. The current-potential curves in supporting electrolytes resemble those for crystalline diamond electrodes (see Figs. 7, 8) the potential window is narrower, however [63], Fluorination of a-C H enhances corrosion resistance of the films significantly [64],... 

Several polymer gel electrolytes were prepared by changing the mixing ratio of ZILs to polymer. The polymer gel electrolytes were obtained as translucent films up to 80 wt% of the ZIL/LiTFSI content. When the content of the ZIL/LiTFSI mixture was less than 40wt%, they were obtained as flexible but white films. Figure 27.4 shows the effect of ZIL/LiTFSI mixture content on the ionic conductivity for polymer gel electrolytes. The ionic conductivity of these polymer gel... 

The HEC cells were constructed from nanocrystalline WO3 films prepared using the peroxo sol-gel route [3] and Pt-coated Sn02 F-glass substrate served as a counter elelectrode. The HEC cells were assembled in such a way that a drop of the sol (redox electrolyte) was placed on the WO3 film and immediately covered with a Pt counter electrode [10]. No sealing of the HEC cells was used the electrolyte gelled inside the HEC. 

Many approaches have been developed for the production of ionic liquid-polymer composite membranes. For example, Doyle et al. [165] prepared RTILs/PFSA composite membranes by swelling the Nafion with ionic liquids. When 1-butyl, 3-methyl imidazolium trifluoromethane sulfonate was used as the ionic liquid, the ionic conductivity ofthe composite membrane exceeded 0.1 S cm at 180 °C. A comparison between the ionic liquid-swollen membrane and the liquid itself indicated substantial proton mobility in these composites. Fuller et al. [166] prepared ionic liquid-polymer gel electrolytes by blending hydrophilic RTILs into a poly(vinylidene fiuoridej-hexafluoropropylene copolymer [PVdF(HFP)] matrix. The gel electrolytes prepared with an ionic liquid PVdF(HFP) mass ratio of 2 1 exhibited ionic conductivities >10 Scm at room temperature, and >10 Scm at 100 °C. When Noda and Watanabe [167] investigated the in situ polymerization of vinyl monomers in the RTILs, they produced suitable vinyl monomers that provided transparent, mechanically strong and highly conductive polymer electrolyte films. As an example, a 2-hydroxyethyl methacrylate network polymer in which BPBF4 was dissolved exhibited an ionic conductivity of 10 S cm at 30 °C. 

Forty and co-workers have used electron yield EXAFS to study (ex-situ) anodic films on aluminum prepared in tartrate and phosphoric acid electrolytes. The A1—O distance is different for the two film preparations. They conclude from these studies that in the tartrate formed film 80% of the aluminum ions are in octahedral sites and 20% in tetrahedral sites whereas for the films formed in phosphoric acid all of the aluminum ions appear to be located at tetrahedral sites. In addition, immersion of the phosphoric acid generated films into water at 85° C for 4 hr. gave rise to dramatic changes in the structure which were ascribed to hydration. (Fig. 13) No such changes were noted for the films generated in tartrate electrolyte. 

Besides advantages outlined in the introduction, the reagent electrode also has some disadvantages that limit its use. The necessary conductivity of the supporting electrolyte makes preparative scale electrolyses below — 50°C difficult because of the increased resistance of the electrolyte. Sometimes the electrode surface becomes deactivated by insulating films (passivation, see Section 2.6.2.4). However, the most serious drawback is the lack of experience with the method, which makes the potential user rather take a chemical oxidant or reductant from the shelf. Therefore, the practice of electroorganic synthesis, which involves electrodes, electrolyte, elec-troanalytical investigation of the substrate and preparative scale electrolysis will be addressed briefly in the next section. 

Fig. 3. SEM micrographs of anodic alumina films prepared in (a) basic electrol3fte mixture containing KH2PO4, NH4(H2P04) and Na2C03 (b) electrolyte (a) + Ni(CH3COO)2 (c) electrolyte (a) + (NH4)2Cr04 (d) electrolyte (a) + (NH4)sMo7024.

The electrolytes were prepared using water, ethyl alcohol, ethyleneglycol, dimethylformamide as solvents of the current-conducting additives. The currentconducting additives were tartaric acid, potassium nitrate, ammonium nitrate and aluminum nitrate. The thicknesses of the synthesized AOS films were measured by laser ellipsometer in 5 points on the surface. Their dielectric characteristics were estimated from C-V curves also in 5 points. 

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