Polyethylene polymer electrolytes

Figure 1. Temperature variation of the conductivity for a cross-section of polymer electrolytes. PESc, poly (ethylene succinate) PEO, polyethylene oxide) PPO, polypropylene oxide) PEI, poly(ethyleneimine) MEEP, poly(methoxyethoxy-ethoxyphosphazene) aPEO, amorphous methoxy-linked PEO PAN, polyacrylonitrile PC, propylene carbonate EC, ethylene carbonate.

State-of-the-art thin film Li" cells comprise carbon-based anodes (non-graphitic or graphite), solid polymer electrolytes (such as those formed by solvent-free membranes, for example, polyethylene oxide, PEO, and a lithium salt like LiPFe or LiCFsSOs), and metal oxide based cathodes, in particular mixed or doped oxides... 

Ion exchangers are polymer electrolytes prepared a priori as insoluble solids (salts, acids, bases hydrated, possibly gel-Uke). Their polymer backbone is three-dimensional. Many are polyvinyl compounds (substituted polyethylenes) having the general formula [-CH2-CXH-] , where different substituents X lead to rather different products ... 

D - diffusion coeff., cm /sec. SPE - solid polymer electrolyte PEO - polyethylene oxide AN, THF and other solvents Table II. 

For using lithium batteries (which generally have high energy densities) under extreme conditions, more durable and better conducting electrolytes are necessary. Salt-in-polymer electrolytes discovered by Angell et al. (1993) seem to provide the answer. Polypropylene oxide or polyethylene oxide is dissolved in low melting point mixtures of lithium salts to obtain rubbery materials which are excellent lithium-ion conductors at ambient temperatures. 

Perfluorosulfonic acid (PFSA) - polyelectrolyte PEO polyethylene oxide), and polymer electrolyte... 

Haidar, B., Singru, R.M., Maurya, K.K., Chandra, S. (1996) Temperature dependence of positron-annihilation lifetime, free volume, conductivity, ionic mobility, and number of charge carries in a polymer electrolyte polyethylene oxide complexed with NH4CIO4 . Phys. Rev. B. 54, 7143. 

This review deals with several types of polymer hosts that have been investigated. These include polyethylene oxide and its several modified forms, comb like polymers such as polyacrylates and inorganic polymers such as polyphosphazenes and polysiloxanes. Various instrumental techniques have been employed in the structural characterization of polymer electrolytes. The structural information obtained from methods such as Extended X-ray Absorption Fine Structure (EXAFS), X-ray diffraction methods, vibrational spectroscopy and nuclear magnetic resonance (NMR) have also been discussed. 

Poly(ethylene oxide) is a linear polymer containing the donor oxygen atoms in the main backbone. Some other similar systems known to function as polymer electrolytes include simple poly ethylene glycol (PEG) [145], end acetylated PEG [146], poly propylene oxide (PPO) [ 147-148], poly(/ -propiolactone) [149], polyethylene succinate) [150-151],poly (ethylene adipate) [152],poly (ethylene imine) [153] and poly (alkylene sulfide) [154], Many of these form metal salt complexes. However, conductivities of the order of 10 s S cm are observed only at high temperatures. Table 5 summarizes this data. 

The second type of polymer electrolyte does not itself possess charged moieties along its chain. Rather, the polymer acts as the solvent for electrolyte ions which are able to move through the polymer matrix much as in a liquid electrolyte. Thus, the polymer serves as a solid ionic conductor. An example of this type of polymer is polyethylene oxide in which lithium and other small cations have high mobility [2]. 

A third type of ionic conduction occurs in polymer electrolytes, such as polyethylene oxide. The mechanism of ionic conduction in polymer electrolytes is not entirely understood. However, it is believed to involve rapid polymer segmental motion which creates regions of an elastomeric nature. These elastomeric regions have relaxation times similar to liquids, and, thus, allow a higher ionic mobility than would be concluded from the polymer s macroscopic properties [2]. 

PA was also found to be reduced in organic solvents [314,320,321] or in a solid polymer electrolyte (polyethylene oxide PEO) [321] according to the reaction,... 

Solution polymerization is used for the manufacture of polyethylene, polypropylene, and polystyrene, but by far the most widely used process for polystyrene and PVC is suspension polymerization. In the latter process (also known as bead, pearl, or granular polymerization because of the form in which the final products may be obtained), the monomer is dispersed as droplets (0.01-0.05 cm in diameter) in water by mechanical agitation. Various types of stabilizers, which include water-soluble organic polymers, electrolytes, and water-insoluble inorganic compounds, are added to prevent agglomeration of the monomer droplets. Each monomer droplet in the suspension constitutes a small bulk polymerization system and is transformed finally into a solid bead. Heat of polymerization is quickly dissipated by continuously stirring the suspension medium, which makes temperature control relatively easy. 

Electrodes and cell components must be thin to minimise the internal resistance of the batteries the total cell can be less than 0.2 mm thick. Figure 12.11 shows the construction of a multi-layer film, rechargeable lithium polymer battery, using a solid polymer electrolyte. A thin lithium metal foil acts as an anode. The electrolyte is polyethylene oxide containing a lithium salt, and the cathode is a composite of the electrolyte and a... 

Hayamizu and Akiba measured self-diffusion coefficients of lithium ion, anion and solvent in the electrolytes for lithium batteries. The self-association of some anions is discussed. Sekhon et u/. investigated the diffusive motion of cations and anions in polyethylene oxide based polymer electrolytes. Translational motion was found above Tg. 

Lewandowski, A., Zajder, M., Fr ckowiak, E., Begum, E, 2001. Supercapacitor based on activated carbon and polyethylene oxide-KOH-H20 polymer electrolyte. Electrochim. Acta 46,2777-2780. 

Figure 1,8 Polyethylene oxideAiC104 polymer electrolyte structure.

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