New fast lithium ionic conductor in the Li3NLiILiOH system

The electrical properties of Li₃NLiILiOH (1:2:x molar ratio) compounds are investigated. These quasi-ternary compounds have a cubic crystal structure similar to Li₅NI₂. The Li₃NLiILiOH (1:2:0.77) compound has a conductivity of 0.95 × 10_?1 (S/m at 25°C with an activation enthalpy of 24.6 (kJ/mol). All the compounds investigated are predominantly ionic conductors. The electronic transference number is smaller than 10^?5 and the decomposition voltage of these compounds is about 1.6V at 25°C.     

Etude comparee de la conductivite ionique du lithium dans les halogenoborates vitreux

New vitreous electrolytes with fast lithium ion carriers have been obtained in the B₂O₃Li₂OLiX (X = F, Cl, Br, I) systems. The variation of the ionic conductivity is discussed as a function of Li₂O and LiX concentration. The choice of the halogen is taken in consideration.     

Ionic conductivity of solid lithium ion conductors with the spinel structure: Li2MCl4 (M = Mg,Mn, Fe,Cd)

The ionic conductivity of the polycrystalline samples of the lithium chloride spinel, Li₂MCl₄ (M = Mg, Mn, Fe, Cd) is measured by the help of ac techniques in the temperature range of 25–500°C. The highest conductivity of 0.3 Scm^?1 at 400°C is obtained in Li₂CdCl₄. In addition, the solid solution, Li_2?2δM_1+δCl₄, has been examined. It is found that Li_1.9Cd_1.05Cl₄ has higher conductivity than that of Li₂CdCl₄. The phase transitions of these compounds are also discussed.     

Further studies on the lithium phosphorus oxynitride solid electrolyte

First step in the way to the fabrication of an all-solid microbattery for autonomous wireless sensor node, amorphous thin solid films of lithium phosphorus oxynitride (LiPON) were prepared by radio-frequency sputtering of a mixture target of P₂O₅/Li₂O in ambient nitrogen atmosphere. The morphology, composition, and ionic conductivity were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and A.C. impedance spectroscopy. With a thickness of 1.4 μm, the obtained LiPON amorphous layer provided an ionic conductivity close to 6 × 10⁻⁷ S cm⁻¹ at room temperature. MicroRaman UV spectroscopy study was successfully carried out for the first time on LiPON thin films to complete the characterization and bring further information on LiPON structure.     

Investigation on the stability of Li5La3Ta2O12 lithium ionic conductors in humid environment

In this paper, the stability in humid air of Li₅La₃Ta₂O₁₂ lithium ionic conductors synthesized by conventional solid-state reaction was investigated by internal friction, conductivity, weight variation, X-ray diffraction, and thermogravimetric analysis methods. It was found that when the Li₅La₃Ta₂O₁₂ samples were aged in open air at room temperature, the internal friction peaks associated with the short-distance diffusion of lithium vacancies gradually shift toward higher temperature and increase in height, while the weight of the sample increases and impurity phases of LiOH·H₂O appear. These results reveal that the Li₅La₃Ta₂O₁₂ compounds are unstable against moisture in open air at room temperature. It was suggested that the protons from the moisture substitute the lithium ions in Li₅La₃Ta₂O₁₂ samples to form Li₂O and new protonic derivatives, Li_5−x La₃Ta₂O_12−x (OH) _x (0<x<2.15), and the resultant Li₂O may react further with water to form LiOH·H₂O.     

Topochemical reactions of rutile related structures with lithium

The topochemical lithiation of rutile related MO₂ with n-BuLi, and in nonaqueous lithium electrochemical cells is reported. This series illustrates the importance of electronic conductivity and cell volume to substantial lithium incorporation. The Li_xMO₂ compounds are metastable and decompose at temperatures less than 250°C.     

Sol-gel processing of lithium disilicate

Lithium silicate powders were prepared by several sol-gel routes. Starting solutions contained equimolar amounts of lithium and silicon, but single-phase lithium disilicate (Li₂Si₂O₅) formed only when local stoichiometry was maintained through gelation and drying. Gels prepared from solutions containing LiNO₃, tetraethylorthosilicate (TEOS), water and ethanol were visibly homogeneous, but on drying the local stoichiometry was upset by the recrystallization of LiNO₃. Consequently, a lithium-rich phase (Li₂SiO₃) was the first to crystallize on heating with a lesser amount of Li₂Si₂O₅ forming at a higher temperature. Solutions containing TEOS and lithium methoxide formed a precipitate when combined with a water/ethanol hydrolysis solution. The precipitate dissolved before gelation, but the resulting powders crystallized into a mixture of Li₂SiO₃ and Li₂Si₂O₅. The relative amount of Li₂Si₂O₅ could be increased by adding HNO₃ to the hydrolysis solution and using lower water contents. Precipitation was avoided by partially hydrolysing TEOS before adding the lithium alkoxide; these powders crystallized directly into Li₂Si₂O₅ after heating at 550 °C. Gel-derived powders prepared using an Li-Si methoxyethoxide solution also crystallized directly into Li₂Si₂O₅.     

Electrical conductivity of polycrystalline lithium vanadium bronzes

Polycrystalline lithium vanadium bronzes, Li _x V₂O ₅ with different values of x have been prepared by both high temperature synthesis and room temperature chemical lithiation techniques. Electrical conductivity of the specimens initially increases with lithium concentration. The maximum conductivity is obtained in the phase for the high temperature prepared specimens and in Phase II for the room temperature prepared specimens. V⁴⁺ concentration of the specimens has been measured by a spectrophotometric technique and its variation has been correlated with the preparation condition and conductivity.     

Investigation on the stability of Li<Subscript>5</Subscript>La<Subscript>3</Subscript>Ta<Subscript>2</Subscript>O<Subscript>12</Subscript> lithium ionic conductors in humid environment

In this paper, the stability in humid air of Li₅La₃Ta₂O₁₂ lithium ionic conductors synthesized by conventional solid-state reaction was investigated by internal friction, conductivity, weight variation, X-ray diffraction, and thermogravimetric analysis methods. It was found that when the Li₅La₃Ta₂O₁₂ samples were aged in open air at room temperature, the internal friction peaks associated with the short-distance diffusion of lithium vacancies gradually shift toward higher temperature and increase in height, while the weight of the sample increases and impurity phases of LiOH·H₂O appear. These results reveal that the Li₅La₃Ta₂O₁₂ compounds are unstable against moisture in open air at room temperature. It was suggested that the protons from the moisture substitute the lithium ions in Li₅La₃Ta₂O₁₂ samples to form Li₂O and new protonic derivatives, Li_5?x La₃Ta₂O_12?x (OH) _x (0<x<2.15), and the resultant Li₂O may react further with water to form LiOH·H₂O.     

Intrinsically Optimizing Charge Transfer via Tuning Charge/Discharge Mode for Lithium–Oxygen Batteries

Lithium–oxygen batteries have an ultrahigh theoretical energy density, almost ten times higher than lithium‐ion batteries. The poor conductivity of the discharge product Li₂O₂, however, severely raises the charge overpotential and pulls down the cyclability. Here, a simple and effective strategy is presented for regular formation of lithium vacancies in the discharge product via tuning charge/discharge mode, and their effects on the charge transfer behavior. The effects of the discharge current density on the lithium vacancies, ionic conductivity, and electronic conductivity of the discharge product Li₂O₂ are systematically investigated via electron spin resonance, spin‐alignment echo nuclear magnetic resonance, and tungsten nanomanipulators, respectively. The study by density functional theory indicates that the lithium vacancies in Li₂O₂ generated during the discharge process are highly dependent on the current density. High current can induce a high vacancy density, which enhances the electronic conductivity and reduces the overpotential. Meanwhile, with increasing discharge current, the morphology of the Li₂O₂ changes from microtoroids to thin nanoplatelets, effectively shortening the charge transfer distance and improving the cycling performance. The Li₂O₂ grown in fast discharge mode is more easily decomposed in the following charging process. The lithium–oxygen battery cycling in fast‐discharge/slow‐charge mode exhibits low overpotential and long cycle life.     

Preparation of powders and films of the lithium ion conducting solid electrolyte Li1.3Al0.3Ti1.7(PO4)3

This paper describes a process for the preparation of powders and films of the lithium ion conducting solid electrolyte Li_1.3Al_0.3Ti_1.7(PO₄)₃ from peroxide solutions. The use of peroxide solutions ensures the preparation of Li_1.3Al_0.3Ti_1.7(PO₄)₃ with a room-temperature electrical conductivity of (4?C5) × 10^?4 S/cm by calcining a precursor at 800°C. The synthesized Li_1.3Al_0.3Ti_1.7(PO₄)₃ powders were characterized by X-ray diffraction, thermal analysis (DTA/TG), and ionic and electronic conductivity measurements. The growth of Li_1.3Al_0.3Ti_1.7(PO₄)₃ solid electrolyte films is described.     

Lithium ion conduction in Li5A104, Li5GaO4 and Li6ZnO4

Polycrystalline samples of Li₅Al0₄, Li₅Ga0₄, and Li₆Zn0₄ have been synthesized, and their ionic conductivity measured over a range of temperature. These materials, which have the antifluorite structure with large concentrations of intrinsic cation vacancies, have Arrhenius-like conductivities at low temperatures, with a steep rise in the range 385–450°C, reaching very high values, with a very small temperature dependence, thereafter. Materials of this type, which exhibit the highest values of lithium ion conductivity yet found, may have important practical applications in devices such as elevated temperature batteries.     

Fast ionic lithium conduction in solid lithium nitride chloride

Lithium nitride chloride (Li_1.8N_0.4Cl_0.6) crystallizes in a defect anti-fluorite structure with 10% of the lithium sites being vacant. Its electrical conductivity and thermodynamic stability have been investigated in the temperature range from 25 to 400° C. Lithium ions are the predominant charge carriers, yielding a conductivity temperature product of σ T = 7.456 × 10⁴ exp(?0.49₅ eV/kT) $\text{Ω}{}^{\mathrm{?1}}$ cm^?K. The electronic contribution to the total conductivity is smaller by a factor of less than 10^?4. The material is thermodynamically stable against pure metallic lithium and has a decomposition voltage larger than 2.5 V.     

Intercalation of lithium from Al–Li alloys into lithium titanates

Abstract

An investigation was carried out into the possibility of removing lithium from molten aluminium using insertion compounds. The compounds selected were Li₂O. 3TiO₂ and Li₂O. 2·5 TiO₂ and the structure and degree of insertion were studied. It was found that lithium could be incorporated into the structure, then removed electrochemically.

MST/735     

Bulk ac conductivity studies of lithium substituted layered sodium trititanates (Na<Subscript>2</Subscript>Ti<Subscript>3</Subscript>O<Subscript>7</Subscript>)

Lithium mixed sodium trititanates with 0.3, 0.5 and 1.0 M percentage of Li₂CO₃ (general formula Na_2−X Li _X Ti₃O₇) have prepared by a high temperature solid-state reaction route. EPR analysis, high temperature range (473–773 K) and variable frequency range (100 Hz–1 MHz) ac conductivity measurements were carried out on prepared sample. The lithium ions are accommodated with the sodium ions in the interlayer space. The EPR specta of lithium mixed sodium Trititanates confirm the partial reduction of Ti⁴⁺ ions to Ti³⁺. Four distinct regions have identified in the LnσT versus 1,000/T plots. Various conduction mechanisms which dependence on concentration, frequency and temperature are reported in this paper for lithium mixed layered sodium Trititanates. The dilation of interlayer space has further been proposed to occur due to inclusion of lithium ions in the interlayer space. The conductivity increases as the concentration of lithium increases. The increase of ionic conductivity in these compounds is due to accommodation of lithium ions with sodium ions in interlayer space.     

Lithium intercalation and deintercalation processes in Li4Ti5O12 and LiFePO4

We have studied the kinetics of electrochemical lithium intercalation and deintercalation processes at different currents in lithium iron phosphate and lithium titanate based composite materials containing fine carbon particles. The results demonstrate that lithium intercalation and deintercalation processes in the electrode materials are characterized by an overvoltage: 4 and 2 mV, respectively, for a cell with a lithium titanate based electrode and 4 and 24 mV for a lithium iron phosphate based cell. Li₄Ti₅O₁₂ solubility in Li₇Ti₅O₁₂ is 1.1% (the limit of the solid solution at Li_4.03Ti₅O₁₂), and Li₇Ti₅O₁₂ solubility in Li₄Ti₅O₁₂ is 2.5% (the limit of the solid solution at Li_6.93Ti₅O₁₂). The conductivity of the phosphate and titanate solid solutions involved in the lithium intercalation and deintercalation processes has been determined.     

Conductivity studies of lithium zinc silicate glasses with varying lithium contents

The electrical conductivity of lithium zinc silicate (LZS) glasses with composition, (SiO₂)_0.527 (Na₂O)_0.054(B₂O₃)_0.05(P₂O₅)_0.029(ZnO)_0.34−x (Li₂O) _x (x = 0.05, 0.08, 0.11, 0.18, 0.21, 0.24 and 0.27), was studied as a function of frequency in the range 100 Hz–15 MHz, over a temperature range from 546–637 K. The a.c. conductivity is found to obey Jonscher’s relation. The d.c. conductivity (σ _d.c.) and the hopping frequency (ω _h), inferred from the a.c. conductivity data, exhibit Arrhenius-type behaviour with temperature. The electrical modulus spectra show a single peak, indicating a single electrical relaxation time, τ, which also exhibits Arrhenius-type behaviour. Values of activation energy derived from σ _d.c., ω _h and τ are almost equal within the experimental error. It is seen that σ _d.c. and ω _h increase systematically with Li₂O content up to 21 mol% and then decrease for higher Li₂O content, indicating a mixed alkali effect caused by mobile Li⁺ and Na⁺ ions. The scaling behaviour of the modulus suggests that the relaxation process is independent of temperature but depends upon Li⁺ concentration.     

Li‐Ion Cooperative Migration and Oxy‐Sulfide Synergistic Effect in Li14P2Ge2S16−6xOx Solid‐State‐Electrolyte Enables Extraordinary Conductivity and High Stability

Critical to the development of all‐solid‐state lithium‐ion batteries technology are novel solid‐state electrolytes with high ionic conductivity and robust stability under inorganic solid‐electrolyte operating conditions. Herein, by using density functional theory and molecular dynamics, a mixed oxygen‐sulfur‐based Li‐superionic conductor is screened out from the local chemical structure of β‐Li₃PS₄ to discover novel Li₁₄P₂Ge₂S₈O₈ (LPGSO) with high ionic conductivity and high stability under thermal, moist, and electrochemical conditions, which causes oxygenation at specific sites to improve the stability and selective sulfuration to provide an O‐S mixed path by Li‐S/O structure units with coordination number between 3 and 4 for fast Li‐cooperative conduction. Furthermore, LPGSO exhibits a quasi‐isotropic 3D Li‐ion cooperative diffusion with a lesser migration barrier (≈0.19 eV) compared to its sulfide‐analog Li₁₄P₂Ge₂S₁₆. The theoretical ionic conductivity of this conductor at room temperature is as high as ≈30.0 mS cm^?1, which is among the best in current solid‐state electrolytes. Such an oxy‐sulfide synergistic effect and Li‐ion cooperative migration mechanism would enable the engineering of next‐generation electrolyte materials with desirable safety and high ionic conductivity, for possible application in the near future.     

Synthesis and characterization of new glasses based on Li<Subscript>2</Subscript>S-P<Subscript>2</Subscript>S<Subscript>5</Subscript>-Sb<Subscript>2</Subscript>S<Subscript>3</Subscript> system

There is great interest in sulfide glasses because of their high lithium ion conductivity. New sulfide glasses based on Li₂S-P₂S₅-Sb₂S₃ system have been synthesized by a classical quenching technique. A summary of thermal and structural characterization is presented. Electrical conductivities of the samples have been determined by Impedance Spectroscopy. The compositions of low lithium content (below 20% mol) have presented low electronic conductivities close to 10⁻⁸ S/cm at room temperature. The compositions of medium lithium content (30–50% mol) have presented mixed ionic-electronic behavior with predominant on ionic conductivity with a maximum values around 10⁻⁶ S/cm for samples up to 50% Li₂S at room temperature. Arrhenius behavior is verified between 25°C and T_g for all glasses with activation energies about 0.55–0.64 eV. A comparative study of conductivities with glasses belonging to the other chalcogenide systems has been undertaken.