Polymer/polymeric electrolytes

Chandrasekhar, V. Polymer Solid Electrolytes Synthesis and Structure, Vol 135, pp, 139-206 Charleux, B Faust R Synthesis of Branched Polymers by Cationic Polymerization, Vol. 142, pp. 1-70. 

Boroxine ring-containing polymers have found extensive use in the development of polymeric electrolyte materials used in ion-selective transport membranes. Matsumi and Ohno cover this area in Chapter 6 of this book. 

Note 3 Unlike polymeric electrolytes, in which charge is transported by dissolved ions, charge in intrinsically conducting polymers is transported along and between polymer molecules via generated charge carriers (e.g., holes, electrons). 

Note 2 The terms polyelectrolyte, polymer electrolyte, and polymeric electrolyte should not be confused with the term solid polymer electrolyte. 

Some of the most useful polyphosphazenes are fluoroalkoxy derivatives and amorphous copolymers (11.27) that are practicable as flame-retardant, hydrocarbon solvent- and oil-resistant elastomers, which have found aerospace and automotive applications. Polymers such as the amorphous comb polymer poly[bis(methoxyethoxyethoxy)phosphazene] (11.28) weakly coordinate Li " ions and are of substantial interest as components of polymeric electrolytes in battery technology. Polyphosphazenes are also of interest as biomedical materials and bioinert, bioactive, membrane-forming and bioerodable materials and hydrogels have been prepared. 

Figure 18 Various models proposed for the surface films that cover Li electrodes in nonaqueous solutions. The relevant equivalent circuit analog and the expected (theoretical) impedance spectrum (presented as a Nyquist plot) are also shown [77]. (a) A simple, single layer, solid electrolyte interphase (SEI) (b) solid polymer interphase (SPI). Different types of insoluble Li salt products of solution reduction processes are embedded in a polymeric matrix (c) polymeric electrolyte interphase (PEI). The polymer matrix is porous and also contains solution. Note that the PEI and the SPI may be described by a similar equivalent analog. However, the time constants related to SPI film are expected to be poorly separated (compared with a film that behaves like a PEI) [77]. (With copyrights from The Electrochemical Society Inc., 1998.)...

The commonly used polymeric electrolyte systems include the following types of polymers ... 

The electrochemical behavior of lithium electrodes in a variety of polymeric electrolyte systems was studied extensively by a number of groups, including Scrosati et al. [390-392], Panero et al. [393], Abraham et al. [394-396], Osaka et al. [397-398], Watanabe et al. [399-401], Peled et al. [402], It is clear that there are surface reactions between the lithium and all of the polymeric systems mentioned above. It has already been clearly shown that the ether linkage is attacked by lithium, resulting in the formation of Li alkoxy species [149], Hence, it is expected the PEO-based polymers also react with Li surfaces. Spec-troelectrochemical studies of the Li-PEO system by Scherson et al. [177] provide some evidence for this possibility. Besides the polymers, the polymeric electrolyte systems contain salts with anions such as Aslv,, S03CF3, NlSOTTO),, ... 

Polymeric electrolytes, polymer-salt complexes, and gelled electrolytes, e.g., benzyl sulfonic acid siloxane, polyethylene oxide (imine, succinate)-LiC104, and PVDF gel in THF containing a mixture of Bu2Mg and AlEtCl2, respectively. 

Moreover, polymer film electrolytes have been prepared by polymerization of the imidazole-acid mixtures. The copolymer was synthesized by imidazole... 

In the Current State of the Art we will review some of the recent SANS and reflectivity data from ISIS, which also serve to point to future directions and opportunities. Recent reflectivity measurements, on the adsorption of polymers and polymer/surfactant mixtures at interfaces, surface ordering in block copolymer systems, time dependent inter-diffusion at polymer-polymer interfaces, and the contribution of capillary waves to interfacial widths, will be described. The use of SANS to investigate the dynamic of trans-esterification of polyester blends, the deformation of copolymers with novel morphologies, and the use of diffraction techniques to determine the structure of polymeric electrolytes, will be presented. 

Conductive polymers may be synthesized via either chemical or electrochemical polymerization methods. Electrodeposition of conductive polymers from electrolytes is, thus, feasible provided that the depositing polymer is not soluble in the electrolyte.206 Conductive polymers can be deposited from the electrolytes containing the monomers via either electrooxidation or electroreduction, based on the monomer type used. Similar to that of metals, the electrodeposition of polymers is based on nucleation and growth. The deposition mechanism involves oxidation of monomers adsorbed on the electrode surface, diffusion of the oxidized monomers and oligomerization, formation of clusters, and eventually film growth.213... 

This type of Li battery has already widely diffused in the electronic consumer market, however for automotive applications the presence of a liquid electrolyte is not considered the best solution in terms of safety, then for this type of utilization the so-called lithium polymer batteries appear more convenient. They are based on a polymeric electrolyte which permits the transfer of lithium ions between the electrodes [21]. The anode can be composed either of a lithium metal foil (in this case the device is known as lithium metal polymer battery) or of lithium supported on carbon (lithium ion polymer battery), while the cathode is constituted by an oxide of lithium and other metals, of the same type used in lithium-ion batteries, in which the lithium reversible intercalation can occur. For lithium metal polymer batteries the overall cycling process involves the lithium stripping-deposition at the anode, and the deintercalation-intercalation at the anode, according to the following electrochemical reaction, written for a Mn-based cathode ... 

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. 

Solid state materials that exhibit high ion transport properties are of interest from both academic as well as applied points of view. Polymer solid electrolytes are materials of high technological promise in several electrochemical applications such as high energy density batteries, gas sensors, electrochemical devices etc. These polymeric materials have attracted much attention and hold great promise in this area. 

Polymers that function as solid electrolytes are a subclass by themselves and are known as polymer electrolytes [27,29]. Besides the advantage of flexibility, polymers can also be cast into thin films and since thin films while minimizing the resistance of the electrolyte also reduces the volume and the weight, use of polymer electrolytes can increase the energy stored per unit weight and volume. In view of these attractive features, there has been considerable focus in recent years on the development of both inorganic and organic polymers as electrolytes for ion transport. This article deals with the recent developments in this area with emphasis on the new types of polymeric systems that have been used as polymer electrolytes. 

There are two types of polymeric electrolyte, based on their conduction mechanisms. The first group is the polyelectrolyte in which the polymer itself contains an anionic or cationic group, usually on a side chain. The counter-ions for these groups are typically small, inorganic ions that are mobile within the polymer matrix. Nafion, a perfluorinated sulfonated ionomer made by du Pont, is an example of this type of electrolyte [1]. Nafion has been used as the electrolyte in several amperometric gas sensors. 

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