J. Przyłuski

Effective medium theory in studies of conductivity of composite polymeric electrolytes

The application of effective medium theory to a description of a temperature and composition dependence of conductivity of composite polymeric electrolytes is presented. Conductivities of several composite systems containing conducting (NASICON) or nonconducting (Θ-Al2O3, polyacrylamide) additives are analyzed in terms of effective medium theory approaches. All of the systems studied are based on polyether matrices. The influence of grain size distribution, concentration and type of additives on conductivity of composite systems is discussed. The model presented assumes that an increase in the conductivity in comparison to polyether based electrolytes is due to the formation of highly conductive layers at the polyether matrix-filler interface. Variation of the conductivity of this layer with grain sizes, and the concentration of a filler is assumed and discussed. The theoretical assumptions are confirmed by experimental data obtained by several techniques, such as impedance spectroscopy, DSC, NMR and energy dispersive X-ray diffractometry.

Novel proton conducting composite electrolytes for application in methanol fuel cells

Abstract Proton conducting composite electrolytes based on zeolites dispersed in poly(tetrafluoroethylene) matrix are synthesized and characterized. The ionic conductivity of these composites is analyzed in connection with such features as a sorption of solvents and tensile strength of the composite membrane. Electrolytes exhibiting the highest conductivities are tested in model methanol/oxygen fuel cell working at 70°C. The current densities obtained exceeded 50 mA/cm 2 with the power densities=∼4 mW/cm 2 .

PEO-based polymer blends as materials for solid electrolytes

Abstract Two different methods leading to the preparation of highly conductive polymer solid electrolytes are described. The polymers were modified by the addition of ceramic powders or organic polymers used as crystallization retarders. In both cases the room-temperature ionic conductivities were greatly improved. The reported values of ionic conductivity are higher than 10−5 S/cm at ambient temperatures, which is at least two orders of magnitude higher than for pristine PEO-based systems. The addition of ceramic particles causes an increase in the mechanical and temperature stability of the studied polymer electrolytes. All of the investigated samples are highly amorphous and their structures are stable over time.

Increasing the conductivity of polymer solid electrolytes: A review

Abstract The aim of this work is to present various methods which were investigated to increase the conductivity of polymer electrolytes. Modifications of crystalline structure of PEO-based electrolytes by copolymerization with amorphousizing agents, adding ceramic powders and forming highly amorphous blend type mixtures or grafted copolymers will be described. The review is based on our own results as well as the reports of other authors.

Mixed solid electrolytes based on poly(ethylene oxide)

Polymer solid electrolytes from a PEO-NaI system were mixed with Nasicon and Al2O3 powders. As a result an increase of ionic conductivity exceeding 10−1 S/cm at room temperature was observed for both cases. This increase was due to a higher concentration of amorphous phase which resulted apparently from a higher nucleation rate during the solidification process. The samples were studied using impedance spectroscopy, X-ray diffraction, electron microscopy, NMR, and other techniques.

AC conductivity studies of composite polymeric electrolytes

Ac conductivity studies carried out over a temperature range of 0–100°C for polymeric electrolytes from the PEO-LiClO4-α-Al2O3 system are reported. Electrolytes of various salt concentrations and containing 15 mass% α-Al2O3 are studied. The contribution of charge carrier concentration and ion mobility to the dc ionic conductivity of these composite polymeric electrolytes is discussed. A change in the temperature dependence of ionic conductivity is observed around the melting point of the crystalline phase of the composite electrolytes. An increase in dielectric constant following this phase transition is also observed. Above the melting temperature, an increase in the conductivity depends either on an increase in ionic mobility (samples with low salt concentration) or on the creation of charge carriers (samples with high salt concentration).

Sub-stoichiometric titanium oxides as ceramic electrodes for oxygen evolution—structural aspects of the voltammetric behaviour of TinO2n−1

Oxygen evolution by electrolysis of aqueous solutions has been studied on metallic conducting oxides, known as Magneli phases. The TinO2n−1 ceramic electrodes have been prepared by reduction of TiO2 compacts with hydrogen. The voltammetric behaviour before and after the electrode reaction was investigated and the response of the oxide surface to the anodic polarization was observed. The influence of porosity of the ceramic electrodes on the electrochemical reaction was examined using electrodes of different pore size distributions. The roughness factors of the electrodes were estimated utilizing cyclic voltammetry.

Proton polymeric electrolytes—a review

Abstract The aim of this paper is to summarize recent studies on proton conducting solid polymeric electrolytes. These materials possess a series of important properties suitable for application in various electrochemical devices, such as humidity and hydrogen sensors, smart electrochromic windows, fuel cells and water electrolysers working at ambient temperatures. Studies of polymer protonic electrolytes began a few years ago and until now there is a limited number of papers devoted to fundamental research and applications of these systems. The lack of a review paper summarizing investigations carried out on these compounds prompted us to write this article. The review is based on our own results as well as on investigations described by other authors.

Blend-based and composite polymer solid electrolytes

Abstract It is well known that addition of an inert inorganic substance or a polymer of high glass transition temperature to poly(ethylene oxide)-based polymeric electrolytes improves their mechanical properties and extends their temperature stability range. Several recent papers have shown that such composites or polymeric blends exhibit conductivity values considerably higher than pristine PEO-based electrolytes. In this paper we summarize our studies on polymeric electrolytes based on poly(ethylene oxide) blends with various methacrylic monomers as well as on composite electrolytes containing various inorganic and organic additives. The effects of molecular weight, tacticity, method of blend preparation on conductivity and phase structure of the studied electrolytes are discussed. The results of studies performed on poly(ethylene oxide) composites with aluminas, ceramic and glassy inorganic electrolytes are also presented. Some examples showing the role of low molecular weight plasticizer on properties of polymeric electrolytes are described.

Performance of acrylate-poly(ethylene oxide) polymer electrolytes in lithium batteries

Results for the performance of lithium/Mn02 batteries containing solid polymer electrolytes based on poly(ethylene oxide) blends with some acrylic derivatives are presented. The ionic conductivities of the electrolytes are promising for battery application. It was found, however, that interfacial phenomena impair the battery efficiency. Impedance spectroscopy shows resistive limitations at the anode interface of the batteries, caused either by formation of an electrically distinguishable resistive layer or by chemical interaction between the polymer and lithium, influencing, most probably, the kinetics of the lithium oxidation reaction.