Polyethylene oxide electrolytes

Nagasubramanian G, Distefano S (1990) 12-Crown-4 ether-assisted enhancement of ionic-conductivity and interfacial kinetics in polyethylene oxide electrolytes. J Electrochem Soc 137 3830-3835. doi 10.1149/1.2086309... 

An example of an ionically conductive polymer is polyethylene oxide containing LiC104, which is used as a solid phase electrolyte in batteries. 

Such cells are still produced by Tadiran, and the safety aspects are said to be solved using an electrolyte mixture of polyethylene oxide-methylene oxide which polymerizes with the HF released by hot LiAsFft at 135 °C the electrolyte turns... 

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... 

By contrast, Nal-doped polyethylene oxide membranes have permitted experimental research on tiny rechargeable Na/l2 batteries to be initiated (Figure 2). Chemical stability of the electrolyte, and the integrity of the mechanical contacts at the current collector/electrolyte interfaces, during repetitive cycling, must be improved. 

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

Intercalation of Cjq with lithium has been achieved by solid-state electrochemical doping [125]. In this technique, metallic lithium was used as the negative electrode and a polyethylene oxide lithium perchlorate (P(E0)8liCl04) polymer film served as electrolyte. The formation of stoichiometric phases Li Cgg (n = 0.5, 2, 3, 4, and 12) has been observed. 

Room temperature sensors based on a V2O5-graphite cathode and a polyethylene oxide-based electrolyte were reported by Sathiyamoorthi etal. [55]. The gas is sampled through the porous cathode and for both chlorine and fluorine good sensitivity and rapid response times were observed. 

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. 

The EDLCs, which use all-solid-state ion-conducting polymer [e.g., polyethylene oxide)/LiC104] or polymer gel electrolyte, have also been developed [3],... 

Polyethylene oxide) associates in solution with certain electrolytes (48—52). For example, high molecular weight species of poly(ethylene oxide) readily dissolve in methanol that contains 0.5 wt % KI, although the resin does not remain in methanol solution at room temperature. This salting-in effect has been attributed to ion binding, which prevents coagulation in the nonsolvent. Complexes with electrolytes, in particular lithium salts, have received widespread attention on account of the potential for using these materials in a polymeric battery. The performance of solid electrolytes based on poly(ethylene oxide) in terms of ion transport and conductivity has been discussed (53—58). The use of complexes of poly(ethylene oxide) in analytical chemistry has also been reviewed (59). 

Non-ionic polymers are less dependent on parameters such as pH levels and electrolyte concentration of the surrounding fluids. The main mechanism of mucoadhesion seems to be just physical by interpenetration and subsequent chain entanglement. Some of the polymers such as polyethylene oxide can additionally form hydrogen bonds, but still play only a minor role in macro-molecular drug delivery due to less pronounced mucoadhesive properties than the above-described charged polymers. 

Lead and mercury are deposited as micron-sized clusters, predominantly at intercrystallite boundaries [105] so does lithium from the polyethylene oxide solid electrolyte. What is more, Li intercalates into the sp2-carbon [22, 138], Thus, observations on the Li intercalation and deintercalation enable one to detect non-diamond carbon on the diamond film surface. Copper is difficult to plate on diamond [139], There is indirect evidence that Cu electrodeposition, whose early stages proceed as underpotential deposition, also involves the intercrystallite boundaries [140], We note that diamond electrodes seem to be an appropriate tool for use in the well-known electroanalytical method of detection of traces of metal ions in solutions by their cathodic accumulation followed by anodic stripping. The same holds for anodic deposition, e.g. of, Pb as PbCh with subsequent cathodic reduction [141, 142], Figure 30 shows the voltammograms of anodic dissolution of Cd and Pb cathodically predeposited from their salt mixtures on diamond and glassy carbon electrodes. We see that the dissolution peaks are clearly resolved. The detection limit for Zn, Cd, and Pb is as low as a few ppb [143]. 

Ionically conducting polymers and their relevance to lithium batteries were mentioned in a previous section. However, there are several developments which contain both ionically conducting materials and other supporting agents which improve both the bulk conductivity of these materials and the properties of the anode (Li)/electrolyte interface in terms of resistivity, passivity, reversibility, and corrosion protection. A typical example is a composite electrolyte system comprised of polyethylene oxide, lithium salt, and A1203 particles dispersed in the polymeric matrices, as demonstrated by Peled et al. [182], By adding alumina particles, a new conduction mechanism is available, which involved surface conductivity of ions on and among the particles. This enhances considerably the overall conductivity of the composite electrolyte system. There are also a number of other reports that demonstrate the potential of these solid electrolyte systems [183],... 

In addition, various gel electrolytes were investigated for EDLC as well. Polyethylene oxide) (PEO)-, poly(acrylonitrile) (PAN)-, polymethylmethacrylate) (PMMA)- and poly(vinylidene flouride) (PVdF)-based gel electrolytes, which have been applied for secondary lithium batteries [5-7,50,51,64], were also studied as electrolyte systems for EDLC with carbon electrodes [65-68],... 

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. 

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

MTX MCC mPEG MA NFX PEO PCS PECs PLA PBLA PLG PPO PEG PCL PBLG PBS PGA Methotrexate Crystalline cellulose Monomethoxypoly(ethylene glycol) Maleic acid Norfloxacin Polyethylene oxide) Photon correlation spectroscopy Poly(electrolyte complexes) Poly(L-lactic acid) Poly( 3-benzyl-L-aspartate) Poly (lactide- co -glycolide) Polypropylene oxide) Polyethylene glycol) Poly(e-caprolactone) Poly(y-benzyl-L-glutamate) Phosphate buffered saline Poly(glycolic acid)... 

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. 

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