Z. Florjańczyk

Composite polyether based solid electrolytes

Composite polymeric electrolytes form a new group of solid ionic conductors. Several desirable properties make them suitable for application in various electrochemical devices working over a wide temperature range. In this paper some recent developments in the field of composite polymeric electrolytes are described. A comparison between the properties of composite electrolytes containing inorganic and organic fillers is made. This is based on conductivity data obtained from impedance spectroscopy and structural characteristics based on FT-IR, NMR, DSC and EDX methods. A novel concept concerning the mechanism of ionic transport in composite polymeric systems is proposed.

Composite polyether based solid electrolytes. The Lewis acid-base approach

Abstract The conductivity and phase structure of several composite polyether-alkali metal salt solid electrolytes are analysed and discussed. Species containing Lewis acid centres (AlCl 3 ), Lewis base centres (poly( N , N dimethylacrylamide) as well as those of amphoteric Lewis acid-base character (α-Al 2 O 3 ) are used as fillers. It is suggested that the competition between the Lewis base ether oxygens in the polyether chains and filler Lewis base centres in the complexation of alkali metal cations leads to the formation of different types of complexes and therefore to the modification of the polymer electrolyte ultrastructure. On the other hand acidic centres on the fillers compete with the Lewis acid metal cations in the formation of complexes with the polyether chain. The final ultrastructure and conductivity of composite electrolytes depends on the equilibrium of these Lewis acid-base reactions.

Proton conducting polymer gels based on a polyacrylamide matrix

A reproducible procedure for the preparation of novel proton polymeric electrolytes based on polyacrylamide hydrogels with a H 3 PO 4 additive has been developed and is described. The get membranes are obtained in the form of thin films of reasonable mechanical strength. Their ambient temperature conductivities are in the range 10 -3 to 10 -2 S/cm which corresponds to an ohmic resistance of 1 Ωcm 2 . The effect of H 3 PO 4 and water concentration on the conductivity of the gels prepared is examined in the temperature range from 0-100°C. The protonic conductivity mechanism in the hydrogels studied is postulated on the basis of these investigations. The thermal stability of the electrolytes studied was examined by DSC.

Effects of inhomogeneity on ionic conductivity and relaxations in PEO and PEO-salt complexes

Electrical properties of purified poly(ethylene oxide)-PEO and PEO with dissolved lithium salts, PEO10:LiCF3SO3 and PEO10:LiN(CF3SO2)2, were investigated by impedance spectroscopy. Changes of the impedance spectra during crystallization and melting were recorded. Semicrystalline polymer films exhibited frequency dependence of conductivity with two limiting values of conductivity at low and at high frequency. It was concomitant with dispersion of the electric permittivity exhibiting the low-frequency values of the order of 200. In the case of PEO with dissolved salt, when the film was quasi-amorphous, the electric permittivity also exhibited pronounced dispersion, which was probably due to the presence of crystalline PEO–salt complexes. The dielectric relaxation caused by rearrangement of dipoles in PEO chain was observed at low temperatures and high frequencies.

New route to oligocarbonate diols suitable for the synthesis of polyurethane elastomers

Abstract Oligo(trimethylene carbonate) and oligo(neopentyl carbonate) diols were obtained by the polymerisation of corresponding six-membered cyclic carbonates in the presence of catalysts prepared in the reaction of water with diethylzinc or triethylaluminium. Their structures were proven by means of MALDI TOF and NMR spectroscopic studies. The oligocarbonate diols were reacted with 4,4′-methylenebis(phenyl isocyanate) in the presence of 1,4-butanediol as the chain extender to obtain polyurethane elastomers. The physical and mechanical properties and hydrolytic stability of novel polyurethane elastomers were compared with those of conventional materials based on polyester type soft segments.

Enhancement of ionic conductivity by the addition of plasticizers in cationic monoconducting polymer electrolytes

Abstract Temperature-dependent 7 Li nuclear magnetic resonance (NMR) spin–lattice relaxation time ( T 1 ) data of a lithium monoconducting polymer electrolyte based on maleic anhydride-styrene copolymers are examined in an effort to understand the mechanism of how plasticizers affect significant changes in the observed ionic conductivity ( σ ). The use of strong polar organic plasticizers, such as propylene carbonate, is believed to induce changes in the charge–carrier separation, which is expected to facilitate the transport of ions in these materials. Cationic monoconducting gel electrolytes consisting of polyelectrolytes with immobilized carboxylic anions, charge compensating mobile Li + ions, and various combinations of poly(ethylene glycol) dimethyl ether, dimethylsulfoxide, propylene carbonate, and BF 3 exhibit ambient σ values from 10 −3 to 10 −6 S cm −1 . For systems not containing BF 3 the T 1 data as a function of inverse temperature and the value of the T 1 at its minimum are found to be independent of the electrolyte composition in spite of the fact that the δ values are observed to increase by 1 to 3 orders of magnitude in these samples. For these samples it is suggested that the Li + ions find comparable sites possibly in the form of contact ion pairs with the carboxylic anions and that they are dynamically coupled to the motion of the polymer host. The observed increase in conductivity upon addition of the plasticizers is assumed to arise from a weakening of the ion–polymer interactions and not from a fundamental change in the ionic conductivity mechanism. Upon addition of BF 3 , however, a shift in the T 1 minimum to lower temperatures and a decrease in the depth of the T 1 minimum are observed. These observations suggest that the Li + ions interact preferentially with –O–B ⊖ F 3 moieties and are consistent with the existence of an alternate conduction path such that the ion motions are decoupled from the local motions of the polymer host.

Lithium gel polyelectrolytes based on crosslinked maleic anhydride–styrene copolymer

The effect of various solvents, lithium salts and Lewis acids on the conductivity of crosslinked lithium carboxylates resulting from the modification of maleic anhydride copolymers with styrene has been studied. It was found that in the presence of BF, and polar solvents such as dialkyl sulfoxides or propylene carbonate polyelectrolytes can be obtained in the form of dimensionally stable membranes of ambient temperature conductivity of 10 -3 -10 -4 S.cm -1 . IR studies demonstrate a strong interaction between BF 3 and carboxylic anions leading to a greater mobility of Li + cations. The passivation phenomena at the lithium-gel polyelectrolyte interface for selected systems were examined by means of the impedance spectroscopy. It was found that the passivation layers could be formed in these systems both on the electrode and the polymeric membranes. The passivation process is strongly inhibited in the systems containing BF 3 .

Radiation-modified Nafion membranes for methanol fuel cells

Abstract Nafion membranes modified with vinylphosphonic acid (VPA) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSA) polymers have been obtained and characterized. The membranes were used in methanol fuel cells. Current–voltage profiles were obtained in a Globe Tech GT 60 station adapted to work in a system supplied with methanol. The measurements were conducted in a constant current or constant voltage mode with control of temperature of the cell, fuel and oxygen and control of flow and pressure of methanol and oxygen. It was found that the insertion of VPA into a Nafion membrane increases the power density of the fuel cell.

Application of acrylic polymers in blend-based polymeric electrolytes

Abstract Properties of poly(ethylene oxide) blends with various acrylic polymers as matrices for solid polymeric electrolytes are examined. The highest conductivities are found for systems containing poly(acrylamide) or poly(ethoxy poly(propylene glycol)acrylate) as acrylic additives. The role of interaction between polymer hosts on conductivity and phase structure of blend based electrolyte is discussed using the results of impedance and DSC experiments.

Nonaqueous gel electrolytes doped with phosphoric acid esters

Abstract Highly conducting anhydrous gels doped with phosphoric acid esters have been obtained by entrapping ester solutions in polar aprotic solvents into the poly(vinylidene fluoride) or poly(methyl methacrylate) matrices. The dependence of the physical–chemical properties of these materials on the type and concentration of proton donor, as well as solvent used, are described. It is found that use of propylene carbonate- N , N -dimethyl formamide solvent mixture allows to obtain transparent gels in a wide (5–40 mass%) ester concentration range. Conductivities exceeding 5×10 −4 S cm −1 (PVdF-based systems) and 1×10 −3 S cm −1 (PMMA-based gels) are reported. The mechanism of proton conduction is discussed on the basis of impedance spectroscopy and PFG NMR experiments.