Conductivities and ion association of 1:1 electrolytes in aprotic solvents

Molar conductivities for several alkali metal salts and tetraalkylammonium salts have been measured at 25°C in 4-butyrolactone and propylene carbonate over the concentration range of 0.01–0.001 mol dm^?3. The data were analysed by Justice's method, and the results compared to corresponding data for acetonitrile solutions. From a consideration of dielectric constants, ion pairing is expected to be similar in 4-butyrolactone and acetonitrile solutions. However we find that ion pair formation in 4-butyrolactone is very similar to that in propylene carbonate. When interpreted in terms of the Bjerrum treatment of ion pair formation, this behaviour can be attributed to the formation of solvent separated ion pairs in 4-butyrolactone whereas in propylene carbonate and acetonitrile, all salts form simple “contact” ion pairs.     

Ionic association and mobility in propylene carbonate

Molar conductivities were measured at 298.15 K for symmetric quaternary ammonium picrates, R₄NPic, with R equal to C₁ to C₅ as well as for potassium picrate in propylene carbonate. The molar conductivities at infinite dilution, association constants of ion pairs, ionic conductivities at infinite dilution, and Stokes radii were calculated for the ions employed. The salts, Me₄NPic and Et₄NPic, were found to be dissociated, the others are associated. For the associated salts the data conform to the Fuoss model for the association process.     

Polyoxometalate as co-catalyst of tetrabutylammonium bromide in polyethylene glycol (PEG) for coupling reaction of CO2 and propylene oxide or ethylene oxide

The coupling reaction of CO₂ and propylene oxide or ethylene oxide to produce corresponding cyclic carbonate in the presence of a catalytic system composed of n-Bu₄NBr, α₂-(n-Bu₄N)₉P₂W₁₇O₆₁(Co²⁺ · Br) (abbreviated as P₂W₁₇Co) and PEG (MW 400) has been investigated. The experimental results indicated that the synthesis of propylene carbonate (PC) or ethylene carbonate (EC) achieved with over 98% yield and 100% selectivity within 1 h at 120 °C by using the above catalyst system. When the catalyst system was recycled, the catalytic activity slowly diminished. Moreover, a plausible mechanism was proposed.     

Ethylene carbonate—propylene carbonate mixed electrolytes for lithium batteries

Electrolytic characteristics of propylene carbonate (PC)ethylene carbonate (EC) mixed electrolytes were studied, compared with those in PC electrolytes. Conductivity and Li charge—discharge efficiency values increased with EC contents increasing. For example, 1 M LiClO₄ECPC (EC mixing molar ratio; [EC]/[PC] = 4) showed the conductivity of 8.5 ohm^?1 cm^?1, which value was 40% higher than that in PC. Also, 1 M LiClO₄ECPC([EC]/[PC] = 5) showed the Li charge—discharge efficiency of 90.5% at 0.5 mA cm^?2, 0.6 C cm^?2, which value was ca. 25% higher than that in PC. ECPC mixed electrolytes were considered to be practically available for ambient lithium batteries in regard to the high Li⁺ ion conductivity and also high Li charge—discharge efficiency.     

Ionic transport behavior in poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) and LiClO4 complex

The effect of LiClO₄ on the ionic transport behavior in poly(ethylene oxide)₂₀-poly(propylene oxide)₇₀-poly(ethylene oxide)₂₀ (P123) polymer electrolyte was studied. Its conductivity reaches maximum as molar ratio between ether O atoms and lithium ions [n(O)/n(Li)] equals 8. The results show that LiClO₄ could interact with P123 well and has impacts on polymer organization and chain dynamics. As LiClO₄ concentration decreases, the glass transition temperature (T_g) decreases and the free ion percentage increases. The tendency of conductivity with LiClO₄ concentration is the result of competing effects between polymer chain mobility and free charge carrier concentration.     

Electrolytic characteristics of mixed solvent electrolytes for lithium secondary batteries

Measurements on conductivity and Li charge-discharge efficiency in various propylene carbonate (PC)-based electrolytes were carried out to obtain electrolytes for Li secondary batteries. Among the electrolytes examined, 2 M LiClO₄—PC—THF (PC/THF volume ratio = $\text{4}\text{6}$) showed 1.6 times higher conductivity of 9.8 × 10^?3 Ω^?1 cm^?1 and also ca. 10% higher Li charge-discharge efficiency of 81.3% at 5 mA cm^?2 (0.3 C cm^?2) than those in 1 M LiClO₄—PC. Generally, Li cycling efficiency increases with increase in electrolyte conductivity. From the analysis made on electrolytic parameters, such as transport number of Li⁺ ion, it was concluded that conductivity and Li cycling efficiency increases were caused by the total effects of lower chemical reactivity of THF to Li and smaller practical Li⁺ ion radius based on Li⁺—THF complex formation.     

Conductance of aerosol-ot in n-propanol at 25°C

Molar conductances have been determined for solutions of Aerosol-OT in n-propanol at 25°C. Analysis of these results with the Fuoss—Hsia conductance equation using a distance parameter d = 13.70 × 10^?10 m yields a limiting molar conductance Λ_∞ = 17.5 ± 0.5 Ω^?1 and an association constant K_A = (27 ± 3) × 10² dm³ mol^?1. The latter is substantially larger than that calculated with the Bjerrum equation.     

Glass electrode response to lithium ion activity. Effects of sodium,potassium, ammonium,tetramethyl-, tetraethyl-, and tetra-n-butyl ammonium ions in water and 50% water-ethanol mixture

Competing effects of Na⁺, K⁺, NH⁺₄ and three quaternary ammonium ions, Me₄N⁺, Et₄N⁺, and n-Bu₄N⁺, on the response of a lithium ion-selective glass electrode have been investigated in water and 50% water-ethanol mixture. The results have been analysed according to an ion-exchange model developed earlier for solutions in propylene carbonate. It appears that the effects of the two groups of cations can be rationalized in terms of the relative ease (or difficulty) or desolvation experienced by a lithium ion, in their presence, prior to its incorporation into the glass phase.     

Synthesis, Characterization and Properties of New Lauryl Amidopropyl Trimethyl Ammoniums

A new lauryl amidopropyl trimethyl ammonium methyl carbonate with the formula CH₃(CH₂)₁₀CONH(CH₂)₃N⁺(CH₃)₃CH₃CO₃ ^? was synthesized via a high pressure process with tertiary amines and dimethyl carbonate, and its chemical structure was confirmed using ¹H-NMR spectra, mass spectral fragmentation, and FTIR spectroscopic analysis. In addition, several quaternary ammonium salts with new counterions X^? (X^?=HCO₃ ^?, HCOO^?, CH₃COO^?, CH₃CH(OH)COO^?) were also synthesized by the ion exchange reaction of methyl carbonate quaternary ammoniums with corresponding acids. The surface activities of these compounds were measured, including surface tension (??), critical micelle concentration and minimum surface area (A _min) at 25?°C. Adsorption and micellization free energies of these quaternary ammonium salts in their solutions showed a good tendency towards adsorption at interfaces. The antimicrobial activities are reported for the first time against representative bacteria and fungi for lauryl amidopropyl trimethyl ammoniums. It was found that the antimicrobial potency was Gram-positive bacteria?>?fungi?>?Gram-negative bacteria.     

The conductance of 1:1 electrolytes in sulfolane in the presence of proton donors at 30°C

The molar conductances of LiCl, LiNO₃, KCHCl₂COO and Na p-(NO₂)C₆H₄O in sulfolane, in the presence of HCl, CH₃COOH, CHCl₂COOH and p-(NO)₂C₆H₄OH have been determined. The data were analysed by the full Pitts equation and interpreted in terms of the ionic association constant (K_A) of the salts K⁺A^? and K⁺RHA^?, and the heteroconjugation constant (K_f) of RHA^?. Values of K_f have been calculated from the ratio of association constant K_A(K⁺A^?)/K_A(K⁺RHA^?).     

Solvent effect on the dissociation of o-nitroanilinium ion in methanol-propylene glycol media at 25°C

The dissociation constants (K_s) of o-nitroanilinium ion have been determined at 25° in methanol, propylene glycol and mixtures of the two components containing 10, 30, 50, 70 and 90 wt. % propylene glycol by spectrophotometric measurements. Standard free energies of transfer, ΔG°_t(B) of o-nitroaniline from methanol to the other solvents have been evaluated from the measurement of solubilities at 25°C. The solvent effect on the proton transfer process of this acid: ΔG°_t[BH⁺?B]_sys = 2.303RT[p(K_s?p(K_m)] has been discussed in terms of the free energies of transfer ΔG°_t from methanol to other solvents, of the uncharged based B, of the hydrochloride of the base (BHCl) computed from the corresponding values for HCl and also of the individual ions assessed from the previous knowledge of ΔG°_t(Cl^?). The corresponding data for the protonated tris(hydroxymethyl)methyl amine [TrisH⁺] and p-nitroanilinium ion in the same solvent system obtained from the literature are also compared. ΔG°_t[BH⁺?B]_sys values for the dissociation of o-nitroanilinium ion have been found to increase less readily with wt.% propylene glycol compared to p-nitroanilinium ion and are in contrast with the decreasing nature of the corresponding values for the TrisH⁺ ion of different chemical nature. Electrostatic effect being negligible in this solvent system, the overall behaviour of these acids is found to be dictated by specific chemical nature of solute-solvent interactions besides the effect of relative solvent basicities.     

Glyme-based nonaqueous electrolytes for rechargeable lithium cells

Poly(ethylene glycol)dimethyl ethers [(CH₃O(CH₂CH₂O)_nCH₃, n = 1, 2, 3, and 4)] are generally known as “glymes”. This study examines the conductivity, lithium ion solvation state and charge-discharge cycling efficiency of lithium metal anodes in glyme-based electrolytes for rechargeable lithium cells. 1 M (M: mol l⁻¹) LiPF₆ was used as the solute. The properties of the glymes were investigated by using a ternary mixed solvent consisting of n-glyme, ethylene carbonate (EC) and methylethylcarbonate (MEC). This was because the solubility of LiPF₆ is far less than 1 M in an n-glyme single solvent. The glyme solutions exhibited higher conductivity and higher lithium cycling efficiency than EC/MEC. The conductivity tended to increase with decreases in ethylene oxide chain number (n) and solution viscosity. The decrease in the solution viscosity resulted from the change in the lithium ion solvation structure that occurred when a glyme was added to EC/MEC. The selective solvation of the glyme with respect to lithium ions was clearly demonstrated by -NMR measurements. The lithium cycling efficiency value depended on the charge-discharge current (I_ps). When n increased there was an increase in lithium cycling efficiency at a low I_ps and a decrease in the reduction potential of the glymes. When the conductivities including those at low temperature (below 0 °C), and charge-discharge cycling at a high current are taken into account, di- or tri-glyme is superior to the other glymes tested here.     

Conductivite electrique totale de systemes a base d'iodure d'argent associe aux ionenes: polyiodure de n-propylene ou n-butylene dimethyl n,n-ammonium et polydiiodure n- butylene n′-propylene tetramethyl n,n,n′,n′- diammonium

Some linear ionenes (m–n), with the general formula {[NMe₂(CH₂)_mNMe₂(CH₂)_n]2I}_p (where Me = methyl group), have been prepared. The (3—3), (4—4) and 4—3) ionic polymers are associated with silver iodide, they provide materials the total electric conductivities of which are higher than that of beta AgI. In the case of the AgI-(3—3) system, the obtained value of the specific conductivity is 0.017 ohm cm⁻¹. This study involves compounds with equivalent AgI contents changing between 75 and 95%.     

Conduction of lithium ions in polyvinylidene fluoride and its derivatives—I

Polymeric solid electrolytes were prepared from the hybrid of poly(vinylidene fluoride) and lithium perchlorate. These were obtained as films having a thickness of about 0.1 mm, and high lithium ionic conductivity [about 10^?5 (S cm^?1)] was observed for the hybrid film containing 20 mol% of lithium perchlorate and 30 mol% of propylene carbonate at 40°C. The conductivity depended on the content of lithium perchlorate and additives having high boiling temperature and high dielectric constant. Higher conductivity about 10^?5 (S cm^?1) could be obtained by setting a suitable composition of these three components, ie, poly(vinylidene fluoride), lithium perchlorate and additives. Lithium perchlorate was observed to be dispersed homogeneously in the hybrid film with suitable composition from X-ray diffraction measurement. However, an excess of the micro salts were incorporated as micro crystals in polymer matrix.     

Effect of plasticizers in poly(vinyl alcohol)‐based hybrid solid polymer electrolytes

Hybrid solid polymer electrolyte films consisting of poly(vinyl alcohol) (PVA), poly(methyl methacrylate) (PMMA), LiBF₄, and ethylene carbonate/propylene carbonate (EC/PC) were prepared with a solvent‐casting technique. The complexation was investigated with Fourier transform infrared and X‐ray diffraction. The ionic conductivities of the electrolyte films were determined with an alternating‐current impedance technique for various temperatures in the range of 302–373 K. The maximum conductivity value, 1.2886 × 10^?3 S/cm, was observed for a PVA–PMMA–LiBF₄–EC complex. Thermogravimetry/differential thermal analysis was performed to ascertain the thermal stability of the electrolyte with the maximum conductivity value. For an examination of the cyclic and reversible performance of the film, a cyclic voltammetry study was carried out. The surface morphology of the EC‐and PC‐based electrolytes was examined with scanning electron microscopy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2794–2800, 2003     

Electrical conductivity of some hydroxyapatites

The electrical conductivity of hydroxyapatite, M₁₀(PO₄)₆(OH)₂ (M = Ca, Sr, Ba, Cd, Pb….), has been measured in the temperature range from 200°C to 800°C. The nature of charge carriers in Ca₁₀(PO₄)₆(OH)₂ and Pb₁₀(PO₄)₆(OH)₂ is examined by the emf measurement and the electrolysis experiment. These results suggested that the OH^? ion is the charge carrier in calcium-hydroxyapatite, and the OH^? ion and the electron in lead—hydroxyapatite.     

Ionic conductivity of hybrid films based on polyacrylonitrile and their battery application

The alternate current (AC) and direct current (DC) ionic conductivity of hybrid films composed of polyacrylonitrile (PAN), lithium perchlorate (LiClO₄), and a plasticizer was studied. Three kinds of the plasticizer [ethylene carbonate (EC), propylene carbonate (PC), N,N-dimethylformamide (DMF)] were used. Suitability of these hybrid films for lithium battery was investigated. The AC conductivity, which represents bulk ionic conductivity, was dependent on the component and the composition of the hybrid films, ranging from 10^?4?10^?8 Scm^?1. The AC conductivity was mainly determined by the molar ratio of [plasticizer]/[LiClO₄] in the hybrid films and increased with the increase in this ratio. The effect of the plasticizer on the enhancement in the AC conductivity was in the following order. DMF>EC>PC. The hybrid films with both electrodes of lithium showed the stable DC conductivity of about 1/10 of the AC conductivity, except for the hybrid films containing DMF. The hybrid films were found to be effective as a lithium ionic conductor. The galvanic cell. Li/sample/MnO₂, at the discharge current density of 90 μA/cm² showed the stable electromotive force of about 3 V for 70 h.     

Anionic polymerization of ethylene oxide with cryptates as counterions: 1

A kinetic study of the anionic polymerization of ethylene oxide has been made in tetrahydrofuran at 20°C, with the cryptate K⁺ + [222] as counterion. The ion pair dissociation constant K_D has been deduced from conductivity measurements made on seeds solutions. Some ionic associations higher than cryptated ion pairs could be detected but they are negligible for living end concentrations lower than 6 × 10^?4 mol/l. k_± and k_? were determined from both sets of kinetic data obtained with and without added salt. Free alkoxide ions are one hundred times more reactive than cryptated ion pairs.     

Insertion des ions PF6−, AsF6− et SbF6− dans le graphite par methode electrochimique. caracterisation des produits obtenus

PF₆^?, AsF₆^? and SbF₆^? ions were intercalated into graphite from a propylene carbonate electrolyte by an electrochemical method. During the intentiostatic charging of the system Li-Al/P.C., LiX (molar)/graphite one can observe a continuous increase of potential up to 5.2 V. This value is reached for a C₂₄⁺ charge of the graphite (Fig. 3). The discharge from the intercalated compound of graphite (I.C.G.) presents three plateaus: at 4.7 V until C₄₈⁺, 4 V between C₄₈⁺ and C₉₆⁺ and 2.5 V between C₉₆⁺ and graphite (Fig. 4).X-Ray powder studies (Fig. 5) of C₄₈⁺X^?χ P.C.I.C.G. show that such compound is a second stage one. The anion is solvated by four molecules of propylene carbonate between the layers of graphite. This solvation causes the considerable thickness of the inserted layers (10.6 A for PF₆^? 4 P.C., 10.9 Å for SbF₆^? 4 P.C.). The detailed structure (Fig. 8) of these layers is clarified by intensity line calculations. The presence of four molecules of solvent was confirmed by thermogravimetric measurements (Fig. 6).The first stage compound C₂₄⁺X^? 4 P.C. could not be obtained outside of the cell. The C, P, As and Sb analysis in the I.C.G. provided a composition in good agreement with the formula C_24n⁺ P.C., where n is the stage.Owing to their high potential of 5.2 V against lithium, these compounds are of great interest for their utilisation as cathodes in high energy density batteries.     

High oxide ion conduction in sintered oxides of the system Bi2O3-Y2O3

The ionic conduction in sintered Bi₂O₂-Y₂O₃ was investigated by measuring the conductivity and the emf of an oxygen concentration cell using the specimen tablet as electrolyte. The face centred cubic phase in this system was found to show high oxide ion conduction accompanied by a little electronic conduction when exposed to air. This phase was stable with a composition of 25 ～ 43 mol % Y₂O₃ over a wide range of temperatures, and the oxide ion conductivity increased with decrease in Y₂O₃. The conductivities of (Bi₂O₃)_0.75 (Y₂O₃)_0.25 were 1.6×10^?1 Ω^?1 cm^?1 at 700°C and 1.2×10^?2 Ω^?1 cm^?1 at 500°C values which are many times higher than those of stabilized zirconia (ZrO₂)_0.90(Y₂O₃)_0.10 at corresponding temperatures. Specimens containing less than 25 mol % Y₂O₃ showed a phase transition at 700 ～ 580°C and the conductivities decreased remarkably below these temperatures. High oxide ion conduction in the fcc phase is attributed to the migration of oxide ion vacancies which were present in an appreciable amount.