Lithium Ions (lithium + ion)

Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Terms modified by Lithium Ions

  • lithium ion battery

  • Selected Abstracts


    Single-Molecule Behavior of Dendritic Poly(ethylene glycol) Structures towards Lithium Ions

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 40 2009
    Daihua Tang Dr.
    PEG-ged out! Dendritic poly(ethylene glycol) (PEG) D exhibits excellent single-molecule behavior to lithium ions, and has been characterized by MALDI-TOF-MS and TOF-ESI-MS. Since commercially available linear PEG structures are not monocomponent, constructing dendritic structures may become a good strategy to achieve higher molecular-weight PEG moieties. [source]


    Research on Advanced Materials for Li-ion Batteries

    ADVANCED MATERIALS, Issue 45 2009
    Hong Li
    Abstract In order to address power and energy demands of mobile electronics and electric cars, Li-ion technology is urgently being optimized by using alternative materials. This article presents a review of our recent progress dedicated to the anode and cathode materials that have the potential to fulfil the crucial factors of cost, safety, lifetime, durability, power density, and energy density. Nanostructured inorganic compounds have been extensively investigated. Size effects revealed in the storage of lithium through micropores (hard carbon spheres), alloys (Si, SnSb), and conversion reactions (Cr2O3, MnO) are studied. The formation of nano/micro core,shell, dispersed composite, and surface pinning structures can improve their cycling performance. Surface coating on LiCoO2 and LiMn2O4 was found to be an effective way to enhance their thermal and chemical stability and the mechanisms are discussed. Theoretical simulations and experiments on LiFePO4 reveal that alkali metal ions and nitrogen doping into the LiFePO4 lattice are possible approaches to increase its electronic conductivity and does not block transport of lithium ion along the 1D channel. [source]


    Lewis acid,base property of P(VDF- co -HFP) measured by inverse gas chromatography

    JOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008
    Baoli Shi
    Abstract Poly (vinylidene fluoride- co -hexafluoropropylene) P(VDF- co -HFP) is an excellent material for polymer electrolytes of lithium ion battery. To enhance the lithium ion transference number, some metal oxides were often embedded into P(VDF- co -HFP). The promising mechanism for the increase in lithium ionic conductivity was Lewis acid-base theory. In this experiment, the Lewis acid,base properties of P(VDF- co -HFP) were measured by inverse gas chromatography (IGC). The Lewis acid constant Ka of P(VDF- co -HFP) is 0.254, and the base constant Kb is 1.199. Compared with other polymers characterized by IGC, P(VDF- co -HFP) is the strongest Lewis basic polymers. Except aluminum ion, lithium ion is the strongest Lewis acidic ion according to their , value of Lewis acids. Therefore, a strong Lewis acid,base interaction will exist between lithium ion and P(VDF- co -HFP). This will restrict the transference of lithium ion in P(VDF- co -HFP). To enhance the lithium ion transference by blending other metal ions into P(VDF- co -HFP), it is suggested that the preferential ions should be Al3+, Mg2+, Na+, and Ca2+ because these metal ions have relative large , values. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]


    Single Radiation-Induced Grafting Method for the Preparation of Two Proton- and Lithium Ion-Conducting Membranes

    MACROMOLECULAR MATERIALS & ENGINEERING, Issue 8 2006
    Mohamed Mahmoud Nasef
    Abstract Summary: Two distinct types of polymer electrolyte membranes for conducting protons and lithium ions have been prepared by a radiation-induced grafting method. The polymer electrolyte precursor (PVDF- g -PS) is obtained by the simultaneous grafting of styrene onto poly(vinylidene fluoride) (PVDF) followed by one of two specific treatments. This includes sulfonation with a chlorosulfonic acid/dichloromethane mixture to obtain proton (H+)-conducting membranes, or activation with LiPF6/EC/DC liquid electrolyte to obtain lithium ion (Li+)-conducting membranes. The chemical structure of the obtained electrolyte membranes is verified by FT-IR spectroscopy. Differential scanning calorimetry is used to examine the changes in the crystallinity and the thermal properties of both electrolyte membranes during the preparation process. The thermal stability of both electrolyte membranes is also evaluated using thermal gravimetrical analysis. The obtained polymer electrolyte membranes achieve superior conductivity values: 1.61,×,10,3 S,·,cm,1 for Li+ and 5.95,×,10,2 S,·,cm,1 for H+ at room temperature at a polystyrene content of 50%. The results of this work suggest that high quality H+ - and Li+ -conducting membranes can be obtained using a single radiation-induced grafting method. Schematic representation of the single root for preparation of Li+ - and H+ -conducting membranes started by radiation-induced grafting of styrene onto a PVDF film followed by chemical treatment. [source]


    A study on the behavior of a cylindrical type Li-Ion secondary battery under abnormal conditions. Über das Verhalten eines zylindrischen Li-Ionen Akkumulators unter abnormalen Bedingungen

    MATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 5 2010
    S. Kim
    zylindrische Li-Ionen Akkumulatoren; mechanisches Verhalten; abnormale Bedingungen; Separator Abstract Li-ion (lithium ion) secondary batteries are rechargeable batteries in which lithium ions move between the cathode and the anode. Lithium is not as safe as nickel cadmium (NiCd), and the Li-ion battery can under some conditions increase in temperature and ignite abnormal conditions which includes overcharging, being subjected to an impact, or being hit by a projectile. Before studying causes of Li-ion battery explosions, the term "abnormal condition" was defined. Next, to check the mechanical conditions, an impact test by a free falling object of 9.1 kg weight made of steel was carried out. After the impact test, the damage of the separator around the hollow of the jelly roll in the cell was observed. Following this, the same cell's electrochemical conditions were assessed through a heating test to determine the potential thermal runaway. Finally, to analyze the mechanical damage to the Li-ion batteries during the charging and the impact test, a finite element analysis was performed using LS-DYNA and ABAQUS software. A cylindrical type Li-ion secondary battery was selected for the impact test, heating test, and simulation. The test and simulation results provided insights into the extent to which cylindrical cells can endure abnormal conditions. [source]


    Ionic conductivity in poly (L-leucine)1,3-diamino propane,lithium iodide solid polymer electrolyte

    POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 3 2009
    N. H. Kaus
    Abstract The pelletized Poly(L-Leucine)-1,3-diamino propane,lithium iodide (LiI) samples have been prepared by using a low temperature sintering method. Results from impedance spectroscopy have proven this mixture to be a superionic material with maximum conductivity obtained in the range of 10,3,S/cm for the samples containing 50,wt% LiI. The high ionic conductivity achieved was due to the increased number of charge carrier from LiI. Improved conductivity could also be due to hopping of lithium ion through the side chain of polymer. Infrared spectroscopy showed that both LiI and poly amino acid may co-exist together. From the spectra it is revealed that the CO band at 1643,cm,1 shifted to higher wave number indicating that chelation of Li+ may have occurred at oxygen atom. Results from X-ray diffraction show that the prepared samples were partially crystalline in nature. Some of the peaks have disappeared and this confirmed that some complexation has occurred within the sample. Copyright © 2009 John Wiley & Sons, Ltd. [source]


    Habit modification and improvement in properties of potassium hydrogen phthalate (KAP) crystals doped with metal ions

    CRYSTAL RESEARCH AND TECHNOLOGY, Issue 3 2006
    S. K. Geetha
    Abstract Potassium hydrogen phthalate (KAP) single crystals were grown by slow evaporation and slow cooling techniques. The growth procedure like temperature cooling rate, evaporation rate, solution pH, concentration of the solute, supersaturation ratio etc., has been varied to have optically transparent crystals. Efforts were made to dope the KAP crystals with rubidium, sodium and lithium ions. The dopant concentration has been varied from 0.01 to 10 mole percent. Good quality single crystals were grown with different concentrations of dopants in the mother phase. Depending on the concentration of the dopants and the solution pH value, there is modification of habit. Rubidium ions very much improve the growth on the prismatic faces. The transparency of the crystals is improved with rubidium and sodium doping. The role of the dopants on the non-linear optical performance of KAP indicates better efficiency for doped crystals. The grown crystals were characterized with XRD, FT-IR, chemical etching, Vickers microhardness and SHG measurements. The influence of the dopants on the optical, chemical, structural, mechanical and other properties of the KAP crystals was analysed. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim [source]


    Synthesis and characterization of compounds LixMn1+xFe2,2xO4 with spinel structure in the quasiternary system "LiO0,5 , MnOx , FeOx"

    CRYSTAL RESEARCH AND TECHNOLOGY, Issue 1 2006
    C. Wende
    Abstract The thermal decomposition of freeze-dried Li-Mn(II)-Fe(III)-formate precursors was investigated by means of DTA, TG and mass spectroscopy. By the thermal treatment of the prefired precursors between 400 and 1000°C, single phase solid solutions LixMn1+xFe2,2xO4 (0 , x , 1) with cubic spinel structure were obtained. To get single phase spinels, special conditions concerning the temperature T and the oxygen partial pressure p(O2) during the synthesis are required. Because of the high reactivity of the freeze-dried precursors, in comparison with the conventional solid state reaction, the reaction temperature can be lowered by 200°C. The cation distribution and the properties of the Li-Mn-ferrites were studied by chemical analysis, X-ray powder diffraction and magnetization measurements. It was found that for high substitution rates, almost all lithium occupies the tetrahedral coordinated A-sites of the spinel lattice AB2O4, while at small x-values, lithium ions are distributed over the tetrahedral and octahedral sites. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Synthesis and characterization of poly(ethylene oxide- co -ethylene carbonate) macromonomers and their use in the preparation of crosslinked polymer electrolytes

    JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 7 2006
    Anette Munch Elmér
    Abstract Methacrylate-functionalized poly(ethylene oxide- co -ethylene carbonate) macromonomers were prepared in two steps by the anionic ring-opening polymerization of ethylene carbonate at 180 °C, with potassium methoxide as the initiator, followed by the reaction of the terminal hydroxyl groups of the polymers with methacryloyl chloride. The molecular weight of the polymer went through a maximum after approximately 45 min of polymerization, and the content of ethylene carbonate units in the polymer decreased with the reaction time. A polymer having a number-average molecular weight of 2650 g mol,1 and an ethylene carbonate content of 28 mol % was selected and used to prepare a macromonomer, which was subsequently polymerized by UV irradiation in the presence of different concentrations of lithium bis(trifluoromethanesulfonyl)imide salt. The resulting self-supportive crosslinked polymer electrolyte membranes reached ionic conductivities of 6.3 × 10,6 S cm,1 at 20 °C. The coordination of the lithium ions by both the ether and carbonate oxygens in the polymer structure was indicated by Fourier transform infrared spectroscopy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2195,2205, 2006 [source]


    Single Radiation-Induced Grafting Method for the Preparation of Two Proton- and Lithium Ion-Conducting Membranes

    MACROMOLECULAR MATERIALS & ENGINEERING, Issue 8 2006
    Mohamed Mahmoud Nasef
    Abstract Summary: Two distinct types of polymer electrolyte membranes for conducting protons and lithium ions have been prepared by a radiation-induced grafting method. The polymer electrolyte precursor (PVDF- g -PS) is obtained by the simultaneous grafting of styrene onto poly(vinylidene fluoride) (PVDF) followed by one of two specific treatments. This includes sulfonation with a chlorosulfonic acid/dichloromethane mixture to obtain proton (H+)-conducting membranes, or activation with LiPF6/EC/DC liquid electrolyte to obtain lithium ion (Li+)-conducting membranes. The chemical structure of the obtained electrolyte membranes is verified by FT-IR spectroscopy. Differential scanning calorimetry is used to examine the changes in the crystallinity and the thermal properties of both electrolyte membranes during the preparation process. The thermal stability of both electrolyte membranes is also evaluated using thermal gravimetrical analysis. The obtained polymer electrolyte membranes achieve superior conductivity values: 1.61,×,10,3 S,·,cm,1 for Li+ and 5.95,×,10,2 S,·,cm,1 for H+ at room temperature at a polystyrene content of 50%. The results of this work suggest that high quality H+ - and Li+ -conducting membranes can be obtained using a single radiation-induced grafting method. Schematic representation of the single root for preparation of Li+ - and H+ -conducting membranes started by radiation-induced grafting of styrene onto a PVDF film followed by chemical treatment. [source]


    A study on the behavior of a cylindrical type Li-Ion secondary battery under abnormal conditions. Über das Verhalten eines zylindrischen Li-Ionen Akkumulators unter abnormalen Bedingungen

    MATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 5 2010
    S. Kim
    zylindrische Li-Ionen Akkumulatoren; mechanisches Verhalten; abnormale Bedingungen; Separator Abstract Li-ion (lithium ion) secondary batteries are rechargeable batteries in which lithium ions move between the cathode and the anode. Lithium is not as safe as nickel cadmium (NiCd), and the Li-ion battery can under some conditions increase in temperature and ignite abnormal conditions which includes overcharging, being subjected to an impact, or being hit by a projectile. Before studying causes of Li-ion battery explosions, the term "abnormal condition" was defined. Next, to check the mechanical conditions, an impact test by a free falling object of 9.1 kg weight made of steel was carried out. After the impact test, the damage of the separator around the hollow of the jelly roll in the cell was observed. Following this, the same cell's electrochemical conditions were assessed through a heating test to determine the potential thermal runaway. Finally, to analyze the mechanical damage to the Li-ion batteries during the charging and the impact test, a finite element analysis was performed using LS-DYNA and ABAQUS software. A cylindrical type Li-ion secondary battery was selected for the impact test, heating test, and simulation. The test and simulation results provided insights into the extent to which cylindrical cells can endure abnormal conditions. [source]


    Phase transitions and transport phenomena in Li0.25Cu1.75Se superionic compound

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 15 2004
    M. Kh.
    Abstract Phase transformation points in Li0.25Cu1.75Se mixed electronic,ionic conductor have been determined by calorimetric, conductometric and thermoelectric measurements. The phase transformation (PT) from triclinic to monoclinic occurs at 403,413 K. At 503,515 K the monoclinic phase is followed by a rhombohedral modification. Both of these PTs are accompanied by drops on the calorimetric curve. At about 653 K observed anomalies in the temperature dependencies of the ionic conductivity, of the chemical diffusion coefficient and the jump of the ionic Seebeck coefficient have been induced by the PT to hexagonal phase. Neutron diffraction studies reveal the cubic structure of Li0.25Cu1.75Se compound (with space group Fm3m) at 773 K. The corresponding PT causes anomalies in the electrical and diffusion properties at 703,713 K. Cu ions are statistically distributed over tetrahedral and trigonal voids in an Fm3m cage; lithium ions randomly occupy 32(f) positions. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Crystallinity, thermal properties, morphology and conductivity of quaternary plasticized PEO-based polymer electrolytes

    POLYMER INTERNATIONAL, Issue 3 2007
    Yan-Jie Wang
    Abstract Quaternary plasticized solid polymer electrolyte (SPE) films composed of poly(ethylene oxide), LiClO4, Li1.3Al0.3Ti1.7(PO4)3, and either ethylene carbonate or propylene carbonate as plasticizer (over a range of 10,40 wt%) were prepared by a solution-cast technique. X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) indicated that components such as LiClO4 and Li1.3Al0.3Ti1.7(PO4)3 and the plasticizers exerted important effects on the plasticized quaternary SPE systems. XRD analysis revealed the influence from each component on the crystalline phase. DSC results demonstrated the greater flexibility of the polymer chains, which favored ionic conduction. SEM examination revealed the smooth and homogeneous surface morphology of the plasticized polymer electrolyte films. EIS suggested that the temperature dependence of the films' ionic conductivity obeyed the Vogel,Tamman,Fulcher (VTF) relation, and that the segmental movement of the polymer chains was closely related to ionic conduction with increasing temperature. The pre-exponential factor and pseudo activation energy both increased with increasing plasticizer content and were maximized at 40 wt% plasticizer content. The charge transport in all polymer electrolyte films was predominantly reliant on lithium ions. All transference numbers were less than 0.5. Copyright © 2006 Society of Chemical Industry [source]


    Structure of lithium benzilate hemihydrate solved by simulated annealing and difference Fourier synthesis from powder data

    ACTA CRYSTALLOGRAPHICA SECTION B, Issue 3 2003
    Asiloé J. Mora
    The crystal structure of lithium benzilate hemihydrate (C14H11OLi+·0.5H2O) was solved from synchrotron powder diffraction data. This compound crystallizes in the monoclinic space group P21/a. The structure was solved via the direct space search for two benzilate fragments using the simulated-annealing program DASH, localization of the lithium ions and water molecule from a difference Fourier map, and a restrained Rietveld refinement (Rwp = 0.0687). The structure is a coordination polymer of [Li2(C14H11O3)2·H2O]2 tetramers building helical fourfold one-dimensional channels parallel to [010]. Inside the channels the tetrahedral coordination spheres of the lithium ions contain hydroxyl and carbonyl groups, and water molecules. The water molecule functions as the cohesive entity forming extended hydrogen-bonded chains running along [010], and bifurcated donor hydrogen bonds with the two nearest carboxylates. At the outer edge of the channels, weaker intermolecular C,H,Ph hydrogen bonds along [100] and [001] contribute to the supramolecular aggregation of the structure. [source]


    Two related lithium calixarene complexes, [p-tert -butylcalix[4]arene(OMe)(OH)2(OLi)]2·4MeCN and {p-tert -butylcalix[4]arene(OH)2(OLi)[OLi(NCMe)2]}2·8MeCN, determined using synchrotron radiation

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2009
    Darren S. Lee
    The crystal structures of acetonitrile solvates of two related lithium calixarene complexes have been determined by low-temperature single-crystal X-ray diffraction using synchrotron radiation. Bis(,-5,11,17,23-tetra- tert -butyl-26,28-dihydroxy-25-methoxy-27-oxidocalix[4]arene)dilithium(I) acetonitrile tetrasolvate, [Li2(C45H57O4)2]·4C2H3N or [p-tert -butylcalix[4]arene(OMe)(OH)2(OLi)]2·4MeCN, (I), crystallizes with the complex across a centre of symmetry and with four molecules of unbound acetonitrile of crystallization per complex. Tetraacetonitrilebis(,-5,11,17,23-tetra- tert -butyl-26,28-dihydroxy-25,27-dioxidocalix[4]arene)tetralithium(I) acetonitrile octasolvate, [Li4(C44H54O4)2(C2H3N)4]·8C2H3N or {p-tert -butylcalix[4]arene(OH)2(OLi)[OLi(NCMe)2]}2·8MeCN, (II), also crystallizes with the complex lying across a centre of symmetry and contains eight molecules of unbound acetonitrile per complex plus four more directly bound to two of the lithium ions, two on each ion. The cores of both complexes are partially supported by O,H...O hydrogen bonds. The methoxy methyl groups in (I) prevent the binding of any more than two Li+ ions, while the corresponding two O-atom sites in (II) bind an extra Li+ ion each, making four in total. The calixarene cone adopts an undistorted cone conformation in (I), but an elliptical one in (II). [source]


    Single-Molecule Behavior of Dendritic Poly(ethylene glycol) Structures towards Lithium Ions

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 40 2009
    Daihua Tang Dr.
    PEG-ged out! Dendritic poly(ethylene glycol) (PEG) D exhibits excellent single-molecule behavior to lithium ions, and has been characterized by MALDI-TOF-MS and TOF-ESI-MS. Since commercially available linear PEG structures are not monocomponent, constructing dendritic structures may become a good strategy to achieve higher molecular-weight PEG moieties. [source]


    Enantiospecific Syntheses of Copper Cubanes, Double-Stranded Copper/Palladium Helicates, and a (Dilithium),Dinickel Coronate from Enantiomerically Pure Bis-1,3-diketones,Solid-State Self-Organization Towards Wirelike Copper/Palladium Strands,

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2008

    Abstract Enantiomerically pure, vicinal diols 1 afforded in a two-step synthesis (etherification and subsequent Claisen condensation) chiral bis-1,3-diketones H2L(S,S) (3,a,c) with different substitution patterns. Reaction of these C2 -symmetric ligands with various transition-metal acetates in the presence of alkali ions generated distinct polynuclear aggregates 4,8 by diastereoselective self-assembly. Starting from copper(II) acetate monohydrate and depending on the ratio of transition-metal ion to alkali ion to ligand, chiral tetranuclear copper(II) cubanes (C,C,C,C)-[Cu4(L(S,S))2(OMe)4] (4,a,c) or dinuclear copper(II) helicates (P)-[Cu2(L(S,S))2] (5) could be synthesized with square-pyramidal and square-planar coordination geometry at the metal center. In analogy to the last case, with palladium(II) acetate double-stranded helical systems (P)-[Pd2(L(S,S))2] (6,7) were accessible exhibiting a linear self-organization of ligand-isolated palladium filaments in the solid state with short inter- and intramolecular metal distances. Finally, the introduction of hexacoordinate nickel(II) in combination with lithium hydroxide monohydrate and chiral ligand H2L(S,S) (3,a) allowed the isolation of enantiomerically pure dinuclear nickel(II) coronate [(Li,MeOH)2,{(,,,)-Ni2(L(S,S))2(OMe)2}] (8) with two lithium ions in the voids, defined by the oxygen donors in the ligand backbone. The high diastereoselectivity, induced by the chiral ligands, during the self-assembly process in the systems 4,8 could be exemplarily proven by circular dichroism spectroscopy for the synthesized enantiomers of the chiral copper(II) cubane 4,a and palladium(II) helicate 6. [source]


    Utilization of Self-Sorting Processes To Generate Dynamic Combinatorial Libraries with New Network Topologies

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2006
    Isabelle Saur Dr.
    Abstract The synthesis of water-soluble, organometallic macrocycles is described. They were obtained by self-assembly in reactions of the half-sandwich complexes [{Ru(C6H5Me)Cl2}2], [{Ru(p -cymene)Cl2}2], [{Rh(Cp)Cl2}2], and [{Ir(Cp*)Cl2}2] with the ligand 5-dimethylaminomethyl-3-hydroxy-2-methyl-4-(1H)-pyridone in buffered aqueous solution at pH 8. The structure of the Ru,(p -cymene) complex was determined by single-crystal X-ray crystallography. Upon mixing, these complexes undergo scrambling reactions to give dynamic combinatorial libraries. In combination with structurally related complexes based on amino-methylated 3-hydroxy-2-(1H)-pyridone ligands, an exchange of metal fragments but no mixing of ligands was observed. This self-sorting behavior was used to construct dynamic combinatorial libraries of macrocycles, in which two four-component sub-libraries are connected by two common building blocks. This type of network topology influences the adaptive behavior of the library as demonstrated in selection experiments with lithium ions as the target. [source]


    A Dispensable Methoxy Group?

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 13 2005
    Phenyl Fencholate as a Chiral Modifier of n -Butyllithium
    Abstract Phenyl fenchol forms a 3:1 aggregate with n -butyllithium (3 -BuLi), showing unique lithium,HC agostic interactions both in toluene solution (1H,7Li-HOESY) and in the solid state (X-ray analysis). Although methoxy,lithium coordination is characteristic for many mixed aggregates of anisyl fencholates with n -butyllithium, endo -methyl coordination to lithium ions compensates for the missing methoxy groups in 3 -BuLi. This gives rise to a different orientation of the fenchane moiety, encapsulating and chirally modifying the butylide unit. [source]


    Octanuclear Oxothiomolybdate(V) Rings: Structure and Ionic-Conducting Properties

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 12 2004
    Charlotte du Peloux Dr.
    Abstract A family of alkali salts of octanuclear oxothiomolybdate rings has been synthesized by crystallization of the [Mo8S8O8(OH)8{HMO5(H2O)}]3, (noted HMo8M3,; M=Mo, W) and [Mo8S8O8(OH)8(C2O4)]2, (noted Mo8ox2,) anions in an aqueous solution of ACl (A=Li, Na, K, Rb). Single-crystal X-ray diffraction experiments have been performed showing that the alkali salts exhibit a similar three-dimensional structure. Disordered alkali ions form columns to which the anionic rings are anchored. Ionic-conductivity measurements on pressed pellets have revealed two different behaviors. The lithium salts of HMo8M3, (M=Mo, W) are moderately good proton conductors at room temperature (,=10,5 S,cm,1) and the profile of conductivity as a function of relative humidity shows that the conductivity is due to surface-proton motion (particle-hydrate-type mechanism). On the other hand, the lithium salt of Mo8ox2, competes with the best crystalline lithium conductors at room temperature (,=10,3 S,cm,1), and 7Li NMR experiments confirm the mobility of the lithium ions along the one-dimensional channels of this material. [source]