Solid-state lithium rechargeable batteries with polypyrrole-based positive electrode materials together with a new polymer electrolyte designed for room temperature applications are investigated. The cyclability and stability data are reported.

A series of elastomeric (urethane crosslinked) polyether electrolytes have been prepared in order to investigate the influence on conductivity of crosslink density, length of uninterrupted polyether chain, number of side chains and plasticizer content. Crosslink density was found to only weakly influence conductivity, but had the expected major effect on elastic modulus. Increases in uninterrupted polyether chain length were also found to enhance conductivity. The number of side chains (acting as an internal plasticizer) was not found to have a marked effect on conductivity within the range studied. The highest room temperature conductivity observed in these non-plasticized elastomers was 3 × 10-5 Ω-1 cm-1. Addition of a low molecular weight plasticizer such as tetraglyme was found to markedly increase the conductivity and lower Tg. The highest room temperature conductivity observed in 50% plasticized elastomeric materials was 10-3 Ω-1cm-1.

Molecular dynamics simulations performed on highly concentrated Coulomb/solvent systems are used to help interpret the transport mechanism in polymer ionics. Using simple Coulomb and Lennard-Jones forces among the ions and a solvent model of a fixed dipole contained in a spherical solvent particle, we investigated the nature of ion pair formation and stability. For a model NaI system, we find that ion pairs decrease with increase in solvent dipole moment or temperature. The latter observation is at variance with experimental results on polymer electrolytes, probably because of entropy terms that do not occur with our simple solvent molecule.

Cryptands and crown ethers increase the cation transport in phosphazene and alkoxyaluminate polyelectrolytes. Vibrational spectroscopy indicates that the increased conductivity originates from reduced ion pairing.

The addition of I2 to PPO/MI and MEEP/MI complexes, where M - Na or Li, PPO - poly(propylene oxide), MEEP - methoxyethoxyethoxy phosphazene results in ohmic conductivity. Even in the absence of the metal iodide salt, high conductivities are observed in the polymer/I2 complexes. The presence of polyiodides in all cases is indicated by a Raman band at 170 cm.-1 The width of this peak is found to depend on the concentration of iodine and correlates with increasing conductivity at higher I2 concentrations. An additional feature of the polyiodide complexes is the apparent lack of dependence of conductivity on polymer flexibility as indicated by Tg. In most polymer electrolytes, the conductivity depends upon the glass transition, Tg, with conductivity dropping rapidly at T < Tg. By contrast, the polyiodides show only a small inflection in the conductivity around Tg and substantial conductivity below that temperature. Apparently charge transport dynamics are only weakly coupled to the dynamics of the host polymer. Variable temperature Raman spectroscopy has been employed to investigate the low temperature behavior of polyiodides in PPO/MIn systems.

Ion associations are demonstrated from Raman spectra of the anion symmetric stretch in NaCF3SO3 and LiCF3SO3 containing salt polymer complexes based on PPO and siloxane modified PPO. The observation of increasing amount of ion pairs with increasing molecular weight and temperature can be explained by an entropically driven process. The entropy effect includes contributions from several factors related to transient cross-linking via the cations, conformational entropy of the polymer chains, and free volume dissimilarities between the solvated ions and the macromolecules.

The electrochemistry of polyaniline depends upon the pH of the deposition solution and the nature of the anion present during deposition. When the pH of the deposition solution is below 1.0, the response is typical of the para-substituted phenyleneamine structure. When the pH of the deposition solution is greater than 1.0, an additional voltammetric wave appears, and the response is a function of the dopant anion. This report presents results of an in situ infrared spectroscopic study aimed at elucidating structural features which determine the anion dependent voltammetric response.

The results of several investigations of solvent-free polymer electrolytes by nuclear magnetic resonance (NMR) spectroscopy conducted by the authors and other groups are reviewed. 23Na NMR spectra of a wide variety of amorphous polymer electrolytes are characteristic of the second-order quadrupole broadened central ± 1/2 transition with a distribution of quadrupole couplings. The temperature dependence of the linewidth is similar across a wide range of materials, and highlights the importance of polymer segmental motions above the glass transition temperature to ion mobility. Strong cation-anion interactions in poly(propylene oxide) complexes are indicated by measurements of mobile ion concentrations and, in some cases, the observation of salt precipitation at elevated temperature.

Polymer electrolytes consisting of poly(ethylene oxide) (PEO) complexed with Cu(CF3SO3)2 have been studied by differential scanning calorimetry (DSC), electron spin resonance (ESR) and ionic conductivity measurements. Although motional effects on the ESR spectra are apparent, the present results cannot distinguish between long range Cu2+ transport or the motion of copper ions attached to polyether segments.

The polymer electrolyte PEO:LiBF4 at concentrations 2:1, 4:1, 8:1, 16:1 and pure PEO (in methanol as solvent) was studied in the temperature range 220–340 K using impulsive stimulated light scattering, a time-delayed four-wave mixing (‘transient grating’) technique. We observed longitudinal acoustic waves (the transient density response) and thermal diffusion (leading to the decay of the steady-state density response). The speed of sound and acoustic attenuation rate were determined in the frequency range 57 MHz - 1.4 GHz. From the decay of the steady state response the thermal diffusivities were detremined.

Some features of interest for divalent polymer electrolytes are described. Attention is focussed on two contrasting roles for cations: providing chemical cross-links within the polymer matrix and offering a source of mobile charge carriers. The possible merits of using mixtures of two types of cation, one type for each role, is discussed. Alternative mixed salt systems containing two anions with a common cation are considered. Another class of mixed polymer electrolyte systems involving two divalent cations in conjunction with two monovalent anions is also examined in the context of illustrating competitive anion-cation interactions within the polymer matrix by EXAFS local structure techniques. Results for the systems PE015:ZnI2/Mg(CIO4)2, PEO15:ZnI2/Mg(CF3SO3)2, PEO15:CaI2/ZnI2 and PEO15:CaI2/CaBr2 are discussed.

Taking PEOn:ZnBr2 films as benchmark systems, results are discussed for EXAFS and conductivity studies on the corresponding chloride and iodide systems, and DSC results are also compared with PEOn:NiBr2 samples. The polymer electrolyte films used in this study were cast from water. In each case attention was focused on the behaviour resulting from three different preparation/storage regimes, referred to in the text as U, D50 and D140. The high temperature drying regime D140, produces high melting crystalline complexes in all cases but the low temperature regime, D50, invokes more complicated behaviour. Nickel systems are imperfectly dried by the latter regime whereas it appears possible to dry zinc systems completely in a manner that avoids high melting complex formation. EXAFS reveals that the local structure in the zinc halide systems depends more on anion type than concentration. An interesting minimum is observed in the conductivity against composition curves for the zinc systems subjected to the low temperature drying regime; this can be explained by an ion-pair conduction mechanism.

Long term (1 year) dry storage of the benchmark system caused comparatively little change in the properties.

The complex formation and morphology of the NdCI3—PEO system are presented together with some preliminary results on the Nd(DPM)3 \Nd—tris—2,2,6,6—tetramethyl —3,5—heptane dionate]—PEO system. Although the NdCl3—PEO complex is found to be highly hygroscopic, it is shown that residual moisture can be removed reversibly, thereby permitting the role of water in affecting the morphology of the solid to be examined. It is concluded that complexation is a competitive process between the ether oxygens on the polymer backbone and water. Under anhydrous conditions the resultant complex is amorphous at a \EO]/\NdCl3] molar ratio approximately less than ca. 8, but above this critical value the PEO in excess of the stoichiometric ratio presents a second partially crystalline phase. The glass transition temperatures were found to increase sigmoidally with increasing salt content. Despite the hygroscopic nature of Nd(DPM)3 the resultant complexes were found to be moisture resistant upon prolonged exposure to the atmosphere.

Strategic considerations for the design of new O2--ion solid electrolytes are presented, and preliminary measurements of the oxide-ion conductivity σo = (B/T) exp (-EA/kT) and transport number tO = σO/σ are reported for several oxides with perovsldte-related structures. Ba2In2O5 exhibits a first-order transition at Tt ∼ 930°C from the brownmillerite structure to a cubic perovskite with disordered oxygen vacancies and fast O2-ion conduction. Ba3In2MO8 (M = Ce, Zr, or Hf) contains oxygen vacancies ordered into every second BO2 (001) plane. An octahedralsite preference of the disordered M(IV) cations makes incomplete the oxygen-vacancy ordering, so a high extrinsic σo with EA ∼ 0.6 eV is found for T ≤ 400 °C. The transport properties of Ba3In2ZrO8 at 400 °C are equivalent to those of the stabilized zirconias at 800 °C. BagIn6O17 consists of an intergrowth of (BaO)2 rocksalt and Ba3In3O7.5 oxygen-deficient perovskite layers. Although there is no evidence of long-range ordering of the oxygen vacancies, nevertheless an EA = 1.06 eV and transport properties equivalent to stabilized zirconia indicate retention of short-range correlations to at least 950 °C. Attempts to prepare Bag Y6O17 yielded a mixture of hexagonal Ba3Y4O9 and unidentified phases. An EA = 0.45 eV above a Tt=370 °C gives a remarkable O2--ion conductivity at temperatures T > Tt in both the mixed-phase and pure Ba3Y4O9 at temperatures T > 370 °C, but the samples are extremely hygroscopic.

Layered compounds are known to be among the best host structures to practice lithium intercalation chemistry. Besides geometrical aspects which play an important role but are now quite well understood, this paper emphasizes the mechanism of the charge transfer upon intercalation. Electrochemical and optical spectroscopies associated to transport measurements are used for the investigations of the electronic modifications involved in the charge transfer in lithium intercalated compounds. A selection of appropriate materials is discussed. Optical spectroscopies such as photoluminescence, Raman scattering and far-infrared reflectivity show that free-carrier density and electron mobility change drastically. A good agreement is obtained with the data measurements carried out by transport experiments.

Some features of the electrochemical insertion of hydrogen isotopes into mixed conductors under dynamic electrolytic conditions are discussed. Unusual magnitudes of thermodynamic parameters in both the surface region and the bulk can be obtained under some conditions. These can vary greatly, depending upon the surface composition, as well as experimental conditions. It is thus possible to obtain species distributions and related phenomena inside solids during electrolysis at atmospheric pressure that are equivalent to those that would be present if there were a very high external pressure of one of the components.

The transport of hydrogen isotope interstitial species is very microstructure - dependent. Readily visible microstructural changes occur upon insertion and deletion of these species. This leads to the very sporadic nature of structure - dependent phenomena often observed. These considerations may play an important role in the apparent irreproducibility of experimental observations of the ‘cold fusion’phenomenon.

The voltage of an electrochemical cell, i.e. the difference between the chemical potentials of the two electrodes, may play the role of a sensor which allows to display the structural modifications and the physical properties. The electrochemical processes involved in an alkali metal (A) intercalation electrode emphasize the influence of the ionic and/or electronic features. The A+-lattice and A+-A+ interactions as well as electronic band-filling may lead to phase transitions or even limit the intercalation reaction.

The shape of the cell voltage vs. intercalation rate curve depends on the number of vacant sites available for intercalation, the number and the oxidation state of the reducible cations, the band structure of the material and the covalency of the framework.

Alkali ion intercalation in 3D-structures related to perovskite (Ln⅓ NbO3), hexagonal tungsten bronze (LiW3O9F) and Nasicon-type (AM2 (PO4)3) is discussed from that point of view.

In Ln⅓NBO3 (Ln = La, Nd) (i.e. ▭ ½Ln⅓ ▭, ⅙NbO3) L1+-intercalation in various sites is related to the rare earth size.

Two extra lithium atoms can be introduced into LiW3O9F in which four sites are available, but only one out of two is occupied in order to reduce the electrostatic interactions. Moreover the change in the discharge curves can be associated to the modifications with intercalation rate of the Li+-lattice interactions.

Within the Nasicon derived structures of ATi2 (PO4)3 and Fe2 (MoO4)3 the intercalation process is limited by the lowest stable oxidation state of titanium or iron. In both systems the strong electronic localization leads to formation of large two phase-domains.

The relevance of using 3D-intercalation electrodes in electrochemical power batteries will be discussed as far factors such as electrical behavior or absence of significant unit cell modifications of the positive electrodes during the intercalation process are essential for many cycle utilizations.

Chimie douce reactions (hydrolysis and reduction) from layered oxides : NaNiO2, NaxCoO2 and NaNil-xCoxO2 lead to numerous oxyhydroxides and hydroxides which differ by the composition of the intersheet space.

According to the experimental conditions of the hydrolysis reaction, the oxyhydroxides can be unhydrated or intercalated with one or two layers of water molecules. From the most hydrated phases, the other ones can be obtained by chemical, thermal and even mechanical treatment.

The reduction of Co-substituted nickel oxyhydroxides leads to hydroxides in which nickel and cobalt ions are respectively divalent and trivalent. In order to compensate the excess of positive charge in the (Ni, Co)O2 sheet, anions (OH-, CO32-, SO42-, NO3-) are inserted in the Van der Waals gap.

For the highest anion amounts, well ordered α*-type materials are obtained. Water molecules are simultaneously inserted in the interslab space. Their structure is strongly related to the hydrotalcite one. When the amouit of anions in the intersheet space is not sufficient, interstratified materials are obtained. In this case the (Ni,Co)(OH)2 slabs are separated by a layer of CO32- anions and water molecules (α*-type) or by an empty Van der Waals gap (β(II)-type). The amount of α*-type planes in the structure increases with the cobalt amount. All these materials have been characterized by IR spectroscopy which allows to detect the existence of two types of O-H bonds (free in α*-type plane or hydrogen bonded in ²(II)-type plane).

The structure of LiW3O9F is built up of a peculiar stacking of hexagonal tungsten bronze-type layers. Li can be reversibly intercalated in this material, electrochemically or chemically up to the Li3W3O9F composition.

Diffusion coefficients are determined by the Honders method using Li/LiClO4-PC/Lix W3O9F cells which are discharged galvanostatically for given periods of time. This method does not require the knowledge of the Darken factor nor of the material/electrolyte contact area, which are both rather delicate to determine precisely in pratice.

The evolution of D with the intercalation amount exhibits a drastic increase (by three orders of magnitude) from x = 1 to x = 1.15 and a constant and rather high value afterwards. Different sites for the preexisting lithim (x ≤ 1) and the intercalated ones are therefore expected.

7Li NMR spectra have been recorded for various intercalation amounts. For x = 1, two first order quadrupolar signals are observed, corresponding to the sites of the immobile lithium ion. When lithium is intercalated (x = 1.1), another signal is observed, as well as a modification of that of the first lithium, due to intra site mobility. A more important change is observed between x = 1.1 and x = 1.2, which suggests an exchange process. For larger values of x, a single signal is observed, corresponding to mobile Li+ ions.

The sites in which lithium may be intercalated and the diffusion pathways are discussed on the basis of these results.

We have made an investigation of the ion transport properties of single crystals of the naturally occurring clay vermiculite in order to elucidate the mechanism of conductivity including the predominant charge carrier. Measurements of the ion conductivity, magnetic susceptibility and x-ray lattice parameters of ion-exchanged samples strongly suggest that the native cations and not protons are the major current carriers. We have synthesized the hydrogen form and found that it is a much preferred precursor for ion-exchange by other cations allowing the time necessary for ion-exchange to be reduced from several months to around a week.