M. Siekierski

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.

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).

Application of the “universal power law” to the studies of ac conductivity of polymeric electrolytes

Abstract The universal power law describing the relation between dc and ac conductivities is applied to the data obtained for various polymeric electrolytes. Changes of activation energy of conduction, hopping rate, activation energy for ion hopping and activation energy of charge carriers creation are analyzed according to the West-Almond formalism. The obtained results are correlated with the phase structure of the polymeric electrolyte and its ambient temperature ionic conductivity. We find that high conductivity values are measured for systems for which the activation energy of ion hopping is considerably lower compared to the activation energy of charge carriers creation.

Modelling the a.c. conductivity behaviour of composite polymeric electrolytes by the effective medium theory

Abstract The effective medium theory model is applied to fit a.c. conductivities of composite polymeric electrolytes in the wide frequency range (from 5Hz to 13 MHz). The model data are compared with experimentally measured conductivities for the poly(ethylene oxide)-LiClO4-α-Al2O3 electrolyte showing good agreement at ambient temperatures.

Composite polymeric electrolytes based on poly(ethylene oxide) matrix and metallic aluminum filler

Abstract The mixed-phase composite electrolytes have been widely studied. The conductivity enhancement mechanism, which assumes amorphisation of the polymer matrix at the polymer-filler interface, is widely accepted. The contrary effect of the matrix stiffening and thus the decrease of conductivity was observed for a higher concentration of a wide range of inorganic fillers. Finally, the maximum conductivity is observed for 10–20 wt.% of the additive. In this work, a system containing small grains of metallic aluminum is investigated by the means of XRD, DSC, EIS, SEM and FT-IR. Contrary to previous studies, the present system shows maximum conductivity for a much smaller amount of added grains (1–2 wt.%). The highest ambient temperature conductivity value is higher than 5×10 −6 S cm −1 . The observed conductivity is of purely ionic character. The Almond–West Formalism was used to study the mechanism of conductivity in this system.

Conductivity and structural studies of PEO-NH4SCN electrolytes

Abstract The paper summarizes conductivity and structural studies of PEO-NH 4 SCN electrolytes of salt concentration identified by the ether oxygen/ammonium cation ratio ranging between 200 and 3. The impedance and DSC studies are performed during initial heating, cooling and reheating cycles for all salt concentrations. Contrary to previous results recrystallization was observed during cooling, which directly followed the initial heating cycle. Therefore an increase in conductivity observed during cooling can be attributed only to a difference between melting and recrystallization temperatures, the latter of which appears at the lower temperature range. FTIR studies indicate that complexation of ammonium cation via hydrogen bonding to ether oxygen is the most probable way of formation of polymer-salt complex phase. The spectroscopic data suggest that cations are strongly bonded to polyether chains whereas anions are free to move. Therefore charge transfer seems to be due to the transport of anionic species.

Electrochemical properties of polydithienothiophene

Abstract Poly(3,4-b:3′,4′-d:dithienothiophene) (PDTT) is a new electronically conductive polymeric material with a narrow energy gap. The systematic study of the electrochemical polymerization of 3,4-b:3′,4′-d:dithienothiophene (DTT) was made by means of cyclic voltammetry and chronoamperometry. The polymer layer was examined by means of cyclic voltammetry and impedance spectroscopy. The electrochemical and environmental stability of the layer was tested for layers prepared either by potentiostatic deposition or potential scanning. The d.c. conductivity of the PDTT was measured.

Electrochemical Characterization of Novel Hybrid Polymer Electrolytes with Multifunctional Additive

In this article the properties of the electrolyte basing on the product of the reaction of methylalumoxane with oligoethyleneglycols are studied. The electrochemical studies are performed to describe the conductivity and lithium transference number of the system. In addition DSC, SEM, NMR and vibrational spectroscopy studies are used to get more detailed description of the material. Three classes of electrolytes are here taken into consideration. First bases on PEGDME liquid oligoether system modified with the MAO-PEGME branched hetocomposite system. The second one is the branched product itself used as an electrolyte matrix. In the last cas a crosslinked system was obtained by the utilization of PEGDME - PEG mixture. Obtained conductivities were in range of 10(-4) S/cm for liquid like systems and above 10(-5) S/cm for the solid ones. For LiCF3SO3 containing samples lithium transference number was promising in range from 0.35 to 0.5.