Composite polymer electrolytes number

Composite polymer electrolytes based on PVDF (at least 35%) containing lithium salts were studied [140] by a number of techniques including Li NMR. Spin-lattice relaxation measurements were used to show that localised lithium motion is significantly impeded in some samples but not in others. 

The Li transport numbers (t+) of some selected MEEP-based composite-polymer electrolytes which we have determined using the potentiostatic polarization technique are listed in Table 3.4 [17]. Li" " transport numbers... 

The aim of the first part of this chapter is to present recent research on composite polymer electrolytes, both solid and gel, in order to try to clarify the effect of fillers on ionic conduction, transference number, the polymer crystallisation process, mechanical properties and interface properties in polymer electrolytes. 

Table 14.1 Ionic conductivity and transference number of PEO-based composite polymer electrolyte systems (Stephan and Nahm, 2006)...

The lithium polymer battery (LPB), shown schematically in Fig. 7.21, is an all-solid-state system which in its most common form combines a lithium ion conducting polymer separator with two lithium-reversible electrodes. The key component of these LPBs is the polymer electrolyte and extensive work has been devoted to its development. A polymer electrolyte should have (1) a high ionic conductivity (2) a lithium ion transport number approaching unity (to avoid concentration polarization) (3) negligible electronic conductivity (4) high chemical and electrochemical stability with respect to the electrode materials (5) good mechanical stability (6) low cost and (7) a benign chemical composition. 

There is as yet no consolidated opinion as to the optimum electrolyte for lithium-sulfiir batteries. Experiments with solid polymer electrolyte are described, but aprotic electrolyte in a Celgard-type separator commonly used in lithium ion batteries is applied more frequently. A large number of electrolytes has been studied that differ both in solvents and the lithium salt. The greatest acceptance was gained by lithium imide solutions in dioxolane (or in a mixture of dioxolane and dimethoxyethane) and also lithium perchlorate solutions in sulfone. Dissolution of polysulfides in electrolyfe is accompanied by a noticeable increase in viscosity and specific resistance of electrolyte. It is the great complexity of the composition of the electrochemical system and that of the processes occurring therein that prevent as yet commercialization of lithium-sulfiir electrolytes. 

Although in situ infrared spectroscopy has been applied widely in terms of the systems studied, the reflective electrodes employed have been predominantly polished metal or graphite, and so an important advance has been the study of electrochemical processes at more representative electrodes such as Pt/Ru on carbon [107,122,157], a carbon black/polyethylene composite employed in cathodic protection systems [158] and sol-gel Ti02 electrodes [159]. Recently, Fan and coworkers [160] took this concept one step further, and reported preliminary in situ FTIR data on the electro-oxidation of humidified methanol vapor at a Pt/Ru particulate electrode deposited directly onto the Nafion membrane of a solid polymer electrolyte fuel cell that was mounted within the sample holder of a diffuse reflectance attachment. As well as features attributable to methanol, a number of bands between 2200 and 1700 cm were observed in the spectra, taken under shortoperating conditions, the importance of which has already been clearly demonstrated [107]. 

The ion conductivity of the three PEO/PMMA blend compositions, 25/75, 50/50, and 75/25 studied by us increases with ascending LiClO content due to increasing number of free mobile ions as shown in Figure 28. In addition, blend composition with 75 wt% PEO doped with 0 to 12 wt% LiClO displays comparatively higher a values in the order of 10 S cm than the other two blends. Nevertheless, Tan and Johan, (2011) studied the ion conductivity of PEO/PMMA blend polymer electrolyte found that the composition 20 wt% PEO and 80 wt% PMMA is the most miscible proportion for the blend. Figure 28 depicts that the PEO/PMMA 20/80 blend achieves a maximum ion conductivity of 7 x 10 S cm at 10 wt% LiClO, further enhancement in conductivity can be achieved by the addition of a low molecular weight, low viscosity, and high dielectric constant plasticizer, EC. The incorporation of EC facilitates the dissociation of the... 

The main difference between the AFC and PAFC is the gas-tight solid polymer electrolyte membrane, a sohd proton exchange membrane which has as its main function the transport of protons from anode to cathode. To investigate the physical and electrochemical origins of the performance loss in PEFC—operated at different conditions like high current densities, fuel composition (neat H2, H2 -1- lOOppm CO, H2O), flow rates, temperature, air or pure oxygen, etc.—electrochemical impedance studies on different PEFC systems with different electrodes and membranes were performed, as mentioned in Section 4.5.4.1. First impedance measurements and interpretation of FIS performed to characterize PEFC were reported by Srinivasan et al. [1988], Fletcher [1992], Wilson et al. [1993] and Poltarzewski et al. [1992], With increasing research and development effort to improve the PEFC performance and availability of suitable instrumentation the number of publications has increased. 

By producing simple laminated membrane structiu-es (Figure 2) containing the ICP, force generation occurs upon oxidation/reduction of the active polymers, and movement follows. A number of detailed studies on the effect of polymer composition, supporting electrolyte and rate of stimulation on the forces generated,... 

The polymer electrolytes discussed so far suffer from a number of disadvantages. Firstly, they exhibit low conductivities in comparison with liquid or solid (crystalline or glassy) electrolytes at or below room temperature. The best all-amorphous systems have conductivities less than 10 S cm at room temperature. These ambient temperature conductivities may be insufficient in some cases for the power required by a lithium battery. Secondly, the interfacial impedances present at both the lithium anode (passivation) and composite cathode (passivation, contact) are in addition to the ohmic losses in the electrolyte. Thirdly, the lowness of cation transference number, although similar to the values in liquid systems, is a major issue since the total conductivity is lower and could limit the use of solvent-free polymer electrolytes except in the form of extremely thin films or above room temperature. 

This discussion shows that the gel electrolyte must match the use of the battery, requiring optimization of the composition of the gel polymer electrolyte, the supporting salt and its concentration, and the solvent. PAN gel electrolytes made using different solvents, lithium salts, and composition will display different behaviors with respect to the ionic conductivity, lithium-ion transference number, electrochemical window, cyclic voltam-metric behavior, and compatibility with electrodes. Table 11.1 lists the ionic conductivity at room temperature of some gel electrolytes based on PAN. Because the PAN chain contains highly polar -CN groups, which exhibit poor compatibility with lithium metal electrodes, the passivation of the interface between the gel electrolyte and lithium metal electrode is crucial. At the same time, PAN has a high crystallization tendency. At elevated temperatures, the liquid electrolyte and plasticizer will separate therefore, the polymer is modified, mainly by copolymerization and cross-linking. 

Abstract Polymer electrolytes or gel-type polymer electrolytes are interesting alternatives to substitute liquid electrolytes in dye-sensitized solar cells (DSSC).The interest in this research field is growing, reflected in the increased number of papers published each year concerning these materials. This chapter presents a brief review of the history and development of polymer electrolytes aiming at the application in DSSC. Recent improvements achieved by modifications of the composition and by introduction of additives such as inorganic nanofillers, organic molecules and ionic Uquids are described. The stability of DSSC assembled with these materials, and scaling-up of such devices are also discussed. 

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