W. Wieczorek

Modifications of crystalline structure of peo polymer electrolytes with ceramic additives

Abstract Modifications of PEONaI polymer solid electrolytes by adding alumina powders were studied. Conductivity of prepared flexible films was improved at least one order of magnitude in comparison to pristine PEONaI electrolytes. The results were compared with those obtained previously by us for PEO based composite solid electrolytes containing NASICON.

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.

A basic investigation of anhydrous proton conducting gel electrolytes

Abstract The aim of this paper is to summarize recent trends in the studies on nonaqueous proton conducting gel electrolytes. The physical–chemical properties of these systems are described and their relation to the type and concentration of polymer matrix, proton donor as well as the solvent used is discussed. This analysis is performed on the basis of electrochemical (impedance spectroscopy, cyclic voltammetry), spectroscopic (NMR, PFG NMR, FT-IR), and thermogravimetric (DSC) experiments. The proton conduction mechanism is postulated and its dependence on the sample composition is discussed. The possibility of application of proton conducting gels in electrochromic devices is presented.

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.

Temperature dependence of conductivity of mixed-phase composite polymer solid electrolytes

Abstract This paper describes the conductivity data obtained for various polymeric electrolytes containing dispersed inorganic and organic fillers. For all of the systems studied an increase in ambient temperature conductivity in comparison with pristine poly(ethylene oxide)-based electrolytes was achieved. The temperature dependence of the conductivity data can be described by the Arrhenius equation below and above the melting point of the polymer crystalline phase. The relationship between the conductivity pre-exponential factor and the activation energy is discussed according to the Meyer-Neldel rule.

Novel Solid Polymer Electrolytes with Single Lithium-Ion Transport

State-of-the-art poly(ethylene oxide) (PEO)-based polymer electrolytes have a t Li+ much lower than I; it is typically around 0.2-0.3. Thus, the development of single-cation-conductive, solvent-free polymer electrolytes is considered of prime importance for the progress of the technology of lithium batteries. Attempts mainly directed at immobilization of the anion in the polymer architecture have been reported in the past, but with only modest success because this approach generally depresses the conductivity to unacceptably low values. In this work, we report an alternative, new approach based on the addition to the PEO-LiX blend of an anion-trapping supermolecular component. In this way, polymer electrolytes with unity values of t Li+ but still maintaining a true solid configuration combined with appreciable conductivity have been obtained. To our knowledge, this strategy has never been used, and we believe that this breakthrough result is associated with the immobilization of the anion (X - ) by the additive and, possibly, by an ordering of the PEO-LiX system.

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).