Poly electrochemical stability

We report here studies on a polymer fi1m which is formed by the thermal polymerization of a monomeric complex tris(5,5 -bis[(3-acrylvl-l-propoxy)carbonyll-2,2 -bipyridine)ruthenium(11) as its tosylate salt,I (4). Polymer films formed from I (poly-I) are insoluble in all solvents tested and possess extremely good chemical and electrochemical stability. Depending on the formal oxidation state of the ruthenium sites in poly-I the material can either act as a redox conductor or as an electronic (ohmic) conductor having a specific conductivity which is semiconductorlike in magnitude. 

Skotheim et al. [286, 357, 362] have performed in situ electrochemistry and XPS measurements using a solid polymer electrolyte (based on poly (ethylene oxide) (PEO) [363]), which provides a large window of electrochemical stability and overcomes many of the problems associated with UHV electrochemistrty. The use of PEO as an electrolyte has also been investigated by Prosperi et al. [364] who found slow diffusion of the dopant at room temperature as would be expected, and Watanabe et al. have also produced polypyrrole/solid polymer electrolyte composites [365], The electrochemistry of chemically prepared polypyrrole powders has also been investigated using carbon paste electrodes [356, 366] with similar results to those found for electrochemically-prepared material. 

Cyclic voltammetry is also an ideal analytical tool for assessing the electrochemical stability of the polymer films. This is a fundamental requirement for any conducting polymer to be considered for long-term use in electrochemical devices. The use of ionic liquids for the electrochemical cycling of poly(aniline) has been reported to enhance lifetimes to over a million cycles [12], and significant improvements in the cycling stability of poly(pyrrole) have also been reported [32]. 

The introduction of bridging groups on the thiophene ring modifies the physical and chemical properties of the polymers obtained. The energy of the optical absorption is reduced in FEDOT, Fig. 9.2(k), and poly(ijothia-naphthalene), (PITN) (Wudl et al., 1984), so that in the conductive state thin films are transparent. PEDOT shows high electrochemical stability in the oxidised state and, when combined with poly(styrenesulphonic acid) counter ions, can be processed from aqueous solution. 

In addition to the salt in polymer approach as described above, Angell and coworkers have described preparation of polymer-in-salt materials [44] (vide infra). Lithium salts are mixed with small amounts of poly propylene oxide and poly ethylene oxide to afford rubbery materials with low glass transition temperatures. This new class of polymer electrolytes showed good lithium ion conductivities and a high electrochemical stability. 

F. Estrany, R. Ohver, E. Armelin, H.I. Iribaren, F. Liesa, and C. Aleman, Electroactive properties and electrochemical stability of poly(3,4-ethylenediox3dhiophene) and poly(n-methylpyrrole) multi-layered films generated by anodic oxidation. Port. Electrochim. Acta, 25, 55-65 (2007). 

One class of polythiophene derivative has been studied for use in Type I supercapacitors research into poly(3,4-ethylenedioxythiophene) (PEDOT, Figure 9.4J)-based supercapacitors has been driven by PEDOT s superior chemical and electrochemical stability [148] as well as its fast switching times [161]. Carlberg and Inganas [148] demonstrated energy density of 1 Wh/kg at power densities of... 

Some doubts have been raised about the electrochemical stability of poly(2,7-carbazolylene)s due to the high electron density at the free 3- and 6-positions, making oxidation at these sites facile and leading to possible crosslinking or... 

In addition to the P[3MT-MG8] series of MIEC block copolymers prepared in our laboratories, a third series of block copolymers, poly(3-methylthiophene-co-3-octylthiophene)-block-poly[o>-methoxyocta(oxyethylene)methacrylate], abbreviated P[3MT,30T-MG8], have been synthesized. The reason we selected random copolymers of 3MT and 30T for the electronic conductive block is to combine the solubility and fusibility of SOT with the chemical and electrochemical stability of... 

Since the realization in the early 1980s that poly(ethylene oxide) could serve as a Hthium-ion conductor in Hthium batteries, there has been continued interest in polymer electrolyte batteries. Conceptually, the electrolyte layer could be made very thin (5 rm) and so provide higher energy density. Fauteux et al. [47] reviewed the state of polymer electrolyte technology in 1995. To summarize here briefly, a polymer electrolyte with acceptable conductivity (>10 Scm ), transport number (>0.9), mechanical properties, and electrochemical stability to high voltage positives has yet to be developed. Ten years later the situation has not changed. 

The use of EFMs from polymer blends for separators in LIB is to combine the advantages of different polymers, such as mechanical properties, thermal stability, ionic conductivity, and electrochemical stability. Bicomponent and tricomponent fibrous membranes based on PVDF and its copolymers, PAN and PMMA, had been prepared by electrospinning and used as separator in LIBs, including PVDF/PMMA [36], PAN-PVDF [37], PMMA/PVC [38], TPU/PVDF [39, 40], PAN/PMMA/PS [41], PI/PVDF and PI/PAN [42], PVDF/poly(4-vinylpyridine) (P4VP) [43], and nanocrystal cellulose (NCC)/P(VDF-HFP) [44-46]. Their properties and performance in LIBs are summarized in Table 4.1. 

Besides the electrolytes mentioned in Table 11.2, which can be used as plasticizers, other plasticizers can also be used, such as poly(oxyethylene borate), the structure of which is shown in Figure 11.10 [9]. The ionic conductivity at room temperature is greater than 10 S/cm when this plasticizer is added to PMMA. The electrochemical stability is about 4.5 V, and it is thermally stable up to 300°C. The ionic conductivity can be adjusted as needed by changing the number of ethylene oxide units, n. 

M. Vazquez, J. Bobacka, A. Ivaska, and A. Lewenstam. 2002. Influence of oxygen and carbon dioxide on the electrochemical stability of poly(3,4-ethylenedioxy-thiophene) used as ion-to-electron transducer in aU-solid-state ion-selective electrodes. Sensors and Actuators, B Chemical 82(1) 7-13. 

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