Preparation and characterisation of synthetic mixtures of lithium isotopes

Re-certification of the absolute isotopic composition of the natural lithium isotopic reference material (IRM), IRMM-016, requires measurements calibrated by means of synthetic mixtures of highly enriched lithium isotopes. Ten such mixtures were prepared by weighing and mixing of two well characterised, isotopically enriched, Li₂CO₃ compounds. The starting materials, 99.9981% enriched ⁶Li, and 99.9937% enriched ⁷Li, were purified by ion exchange, and the purified materials converted from LiOH to Li₂CO₃ by reaction with CO₂. Ten new mixtures were prepared by mixing different weighed amounts of these dissolved Li₂CO₃ carrier compounds. The compounds had an estimated level of impurities of 100 ± 100 μg · g^–1 (expanded uncertainty with a coverage factor of 2). In the ten mixtures, the n(⁶Li)/n(⁷Li) ratio varies from 0.025 to 14 and the achieved expanded relative uncertainty on the amount ratio prepared is typically 2 · 10^–4. These mixtures were then used to determine the correction factor, K, for mass discrimination of the measurement procedure and instrument concerned.     

Synthesis,Crystal Structure and Lithium Motion of Li8SeN2 and Li8TeN2

The compounds Li₈EN₂ with E = Se, Te were obtained in form of orange microcrystalline powders from reactions of Li₂E with Li₃N. Single crystal growth of Li₈SeN₂ additionally succeeded from excess lithium. The crystal structures were refined using single‐crystal X‐ray diffraction as well as X‐ray and neutron powder diffraction data (I4₁md, No. 109, Z = 4, Se: a = 7.048(1) Å, c = 9.995(1) Å, Te: a = 7.217(1) Å, c = 10.284(1) Å). Both compounds crystallize as isotypes with an anionic substructure motif known from cubic Laves phases and lithium distributed over four crystallographic sites in the void space of the anionic framework. Neutron powder diffraction pattern recorded in the temperature range from 3 K to 300 K and X‐ray diffraction patterns using synchrotron radiation taken from 300 K to 1000 K reveal the structural stability of both compounds in the studied temperature range until decomposition. Motional processes of lithium atoms in the title compounds were revealed by temperature dependent NMR spectroscopic investigations. Those are indicated by significant changes of the ⁷Li NMR signals. Lithium motion starts for Li₈SeN₂ above 150 K whereas it is already present in Li₈TeN₂ at this temperature. Quantum mechanical calculations of NMR spectroscopic parameters reveal clearly different environments of the lithium atoms determined by the electric field gradient, which are sensitive to the anisotropy of charge distribution at the nuclear sites. With respect to an increasing coordination number according to 2 + 1, 3, 3 + 1, and 4 for Li(3), Li(4), Li(2), and Li(1), respectively, the values of the electric field gradients decrease. Different environments of lithium predicted by quantum mechanical calculations are confirmed by ⁷Li NMR frequency sweep experiments at low temperatures.     

Recycling of Primary Lithium Batteries Production Residues

Production waste of primary lithium batteries constitutes a considerable secondary lithium feedstock. Although the recycling of lithium batteries is a widely studied field of research, the metallic residues of non-rechargeable lithium battery production are disposed of as waste without further recycling. The risks of handling metallic Li on a large scale typically prevent the metal from being recycled. A way out of this situation is to handle Li in an aqueous solution, from where it can be isolated as Li₂CO₃. However, the challenge in hydrometallurgical treatment lies in the high energy release during dissolution and generation of H₂. To reduce these process-related risks, the Li sheet metal punching residues underwent oxidative thermal treatment from 300 to 400 °C prior to dissolution in water. Converting Li metal to Li₂O in this initial process step results in an energy release reduction of ∼70 %. The optimal oxidation conditions have been determined by experimental design varying three factors: temperature, Li metal sheet thickness, and residence time. With 96.9±2.6 % almost the entire Li amount is converted to Li₂O, after 2.5 h treatment at 400 °C for a Li sheet thickness of 1.99 mm. Final precipitation with CO₂ yields 85.5±3.0 % Li₂CO₃. Using pure Li sheets, the product Li₂CO₃ is obtained in battery-grade quality (>99.5 %). Non-precipitated Li is recirculated into the process on the stage of dissolving Li₂O, thus avoiding loss of material.     

Determination of lithium isotopic composition by thermal ionization mass spectrometry in seawater

The isotopic composition of lithium in seawater has been determined by thermal ionization mass spectrometry (TIMS) based on the use of lithium hydroxide as the ion source. Isotopic measurements in a reference material supplied by IAEA (L-SVEC Li₂CO₃) were made to check the reproducibility of the method and ⁶Li indicates mobilization of light isotope of lithium form the sediment.     

Determination of diffusion coefficient of lithium in LiMyMn2 ? yO4 spinels using potentiostatic intermittent titration technique

The potentiostatic intermittent titration technique is used to study lithium transport in the LiM _yMn_{2 − y} O₄ compounds with a spinel structure intended for application as cathodic materials in lithiumion and lithium-polymer batteries. The materials are synthesized using the sol-gel method and the melt-impregnation method. Kinetic and diffusion characteristics of the Li _x Mn₂O₄ and Li _x Mn_1.95Cr_0.05O₄ compounds are determined at 25°C as dependent on lithium content 0 < x < 1. The diffusion coefficient of lithium varies significantly in the range of 10⁻¹⁰ to 10⁻¹³ cm²/s under variation of the electrode composition; the surface resistance depends weakly on the concentration of lithium and is 200–500 Ohm cm².     

Air‐Stable Lithium Spheres Produced by Electrochemical Plating

Lithium metal is an ideal anode for next‐generation lithium batteries owing to its very high theoretical specific capacity of 3860 mAh g^?1 but very reactive upon exposure to ambient air, rendering it difficult to handle and transport. Air‐stable lithium spheres (ASLSs) were produced by electrochemical plating under CO₂ atmosphere inside an advanced aberration‐corrected environmental transmission electron microscope. The ASLSs exhibit a core–shell structure with a Li core and a Li₂CO₃ shell. In ambient air, the ASLSs do not react with moisture and maintain their core–shell structures. Furthermore, the ASLSs can be used as anodes in lithium‐ion batteries, and they exhibit similar electrochemical behavior to metallic Li, indicating that the surface Li₂CO₃ layer is a good Li⁺ ion conductor. The air stability of the ASLSs is attributed to the surface Li₂CO₃ layer, which is barely soluble in water and does not react with oxygen and nitrogen in air at room temperature, thus passivating the Li core.     

Structural and Electrochemical Study of Vanadium‐Doped TiO2 Ramsdellite with Superior Lithium Storage Properties for Lithium‐Ion Batteries

Titanium‐oxide‐based materials are considered attractive and safe alternatives to carbonaceous anodes in Li‐ion batteries. In particular, the ramsdellite form TiO₂(R) is known for its superior lithium‐storage ability as the bulk material when compared with other titanates. In this work, we prepared V‐doped lithium titanate ramsdellites with the formula Li_0.5Ti_1?xV_xO₂ (0≤x≤0.5) by a conventional solid‐state reaction. The lithium‐free Ti_1?xV_xO₂ compounds, in which the ramsdellite framework remains virtually unaltered, are easily obtained by a simple aqueous oxidation/ion‐extraction process. Neutron powder diffraction is used to locate the Li channel site in Li_0.5Ti_1?xV_xO₂ compounds and to follow the lithium extraction by difference‐Fourier maps. Previously delithiated Ti_1?xV_xO₂ ramsdellites are able to insert up to 0.8 Li⁺ per transition‐metal atom. The initial gravimetric capacities of 270 mAh g^?1 with good cycle stability under constant current discharge conditions are among the highest reported for bulk TiO₂‐related intercalation compounds for the threshold of one e^? per formula unit.     

Determination of diffusion coefficient of lithium in LiMyMn2 ? yO4 spinels using galvanostatic intermittent titration technique

The galvanostatic intermittent titration technique is used to study lithium transport in the LiM _y Mn_{2 − y} O₄ compounds with a spinel structure intended for application as cathodic materials in lithium-ion and lithium-polymer batteries. Equilibrium intercalation isotherms of the Li _x Mn₂O₄ and Li _x Mn_1.95Cr_0.05O₄ compounds and also their diffusion characteristics are determined at 25°C as dependent on lithium content x, 0 < x < 1. The diffusion coefficient of lithium varies in a complex way in the range of 10⁻¹⁰ to 10⁻¹² cm²/s under variation of the electrode composition.     

Li+ cation coordination in [Li2(CF3SO3)2(diglyme)] and [Li3(C2F3O2)3(diglyme)]

The title compounds, poly­[[[bis(2‐methoxy­ethyl) ether]­lithium(I)]‐di‐μ₃‐tri­fluoro­methanesulfonato‐lithium(I)], [Li₂(CF₃SO₃)₂(C₆H₁₄O₃)]_n, and poly­[[[bis(2‐methoxy­ethyl) ether]­lithium(I)]‐di‐μ₃‐tri­fluoro­acetato‐dilithium(I)‐μ₃‐tri­fluoro­acetato], [Li₃(C₂F₃O₂)₃(C₆H₁₄O₃)]_n, consist of one‐dimensional polymer chains. Both structures contain five‐coordinate Li⁺ cations coordinated by a tridentate diglyme [bis(2‐methoxy­ethyl) ether] mol­ecule and two O atoms, each from separate anions. In both structures, the [Li(diglyme)X₂]^? (X is CF₃SO₃ or CF₃CO₂) fragments are further connected by other Li⁺ cations and anions, creating one‐dimensional chains. These connecting Li⁺ cations are coordinated by four separate anions in both compounds. The CF₃SO₃^? and CF₃CO₂^? anions, however, adopt different forms of cation coordination, resulting in differences in the connectivity of the structures and solvate stoichiometries.     

Ionic processes in solid-electrolyte passivating films on lithium

The electrochemical behaviour of a Li electrode in solutions of LiAlCl₄ in thionyl chloride, LiBF₄ in γ-butyrolactone and LiClO₄ in the mixed solvent propylene carbonate (PC) + dimethoxyethane (DME) in the process of cell storage has been investigated by the methods of electrode impedance spectroscopy and pulse voltammetry. Analogous studies have been carried out in PC + DME solution with the Li electrode coated with a specially formed protecting film of Li₂CO₃. The results have been compared with those obtained earlier for other lithium electrochemical systems. The general regularities of the Li electrode electrochemical kinetics attributed to the process of Li⁺ ion transport through a passivating film coating a lithium surface have been discussed. Received: 22 February 1999 / Accepted: 20 June 1999     

Intercalation processes influence the structure and electrophysical properties of lithium-conducting compounds having defect perovskite structure

The structural features and electrophysical properties of lithium-conducting compounds having defect perovskite structure based on Li_0.5La_0.5Nb₂O₆ and Li_0.5La_0.5TiO₃ were studied using X-ray diffraction and synchrotron analyses, potentiometry, and complex impedance spectroscopy. Intercalated lithium was found to differently influence ion conductance in titanium- and niobium-containing materials. This difference was found to arise from the structural features of the materials. The systems studied have high chemical diffusion coefficients of lithium (D _Li⁺ = 1 × 10⁻⁶ cm²/s for Li_0.5La_0.5Nb₂O₆ and D _Li⁺ = 3.3 × 10⁻⁷ cm²/s for Li_0.5La_0.5TiO₃).     

高效锂离子筛吸附剂MnO2•0.5H2O的软化学合成及吸附性能研究

以MnCl₂•4H₂O, LiOH•H₂O等试剂为初始原料, 采用溶胶-凝胶、水热处理、固化等软化学合成步骤制备了锂离子筛前驱体Li_1.6Mn_1.6O₄, 并经稀盐酸抽锂后得到了高选择性锂离子筛吸附剂MnO₂•0.5H₂O. 着重对合成过程中锂锰比, 氧化剂用量等因素影响进行了探讨, 并对所制备吸附剂的吸附性能进行了研究. 结果表明, 经软化学合成步骤制备的锂离子筛对Li^＋有良好的吸附量和选择性, 在未来从海水、卤水等液态锂资源富集或提取锂的应用中具有很大的潜力.     

Transport Properties of Solid Electrolytes: Effect of the Isotope Composition of Lithium Charge Carriers

The isotope composition of lithium charge carriers is experimentally found to severely affect transport in solid electrolytes -Li₃BO₃, Li₃N, Li₃AlN₂, Li₅SiN₃, Li₆MoN₄, Li₆WN₄, and LiCl. The lithium cation conduction of these decreases with increasing content of ⁶Li or ⁷Li and reaches a minimum at [⁶Li] = [⁷Li]. The activation energy for conduction increases, reaches a maximum in the same compositions, and then diminishes. Rates of spin–lattice relaxation of ⁷Li nuclei in electrolytes are studied by an NMR method at 15–35 MHz. The calculated activation energy for short-range motion (to one interatom distance) of lithium charge carriers in crystal lattices of electrolytes is lower than that for ionic conduction by 2–3 times, which is attributed to two types of correlation (electrostatic, isotopic) of charge carriers.     

Lithium Ion Mobility in Lithium Phosphidosilicates: Crystal Structure, 7Li, 29Si,and 31P MAS NMR Spectroscopy,and Impedance Spectroscopy of Li8SiP4 and Li2SiP2

The need to improve electrodes and Li‐ion conducting materials for rechargeable all‐solid‐state batteries has drawn enhanced attention to the investigation of lithium‐rich compounds. The study of the ternary system Li‐Si‐P revealed a series of new compounds, two of which, Li₈SiP₄ and Li₂SiP₂, are presented. Both phases represent members of a new family of Li ion conductors that display Li ion conductivity in the range from 1.15(7)×10^?6 Scm^?1 at 0 °C to 1.2(2)×10^?4 Scm^?1 at 75 °C (Li₈SiP₄) and from 6.1(7)×10^?8 Scm^?1 at 0 °C to 6(1)×10^?6 Scm^?1 at 75 °C (Li₂SiP₂), as determined by impedance measurements. Temperature‐dependent solid‐state ⁷Li NMR spectroscopy revealed low activation energies of about 36 kJ mol^?1 for Li₈SiP₄ and about 47 kJ mol^?1 for Li₂SiP₂. Both compounds were structurally characterized by X‐ray diffraction analysis (single crystal and powder methods) and by ⁷Li, ²⁹Si, and ³¹P MAS NMR spectroscopy. Both phases consist of tetrahedral SiP₄ anions and Li counterions. Li₈SiP₄ contains isolated SiP₄ units surrounded by Li atoms, while Li₂SiP₂ comprises a three‐dimensional network based on corner‐sharing SiP₄ tetrahedra, with the Li ions located in cavities and channels.     

Studies on the effects of coated Li2CO3 on lithium electrode

Although a lithium metal anode has a high energy density compared with a carbon insertion anode, the poor rechargeability prevents the practical use of anode materials. A lithium electrode coated with Li₂CO₃ was prepared as a negative electrode to enhance cycleability through the control of the solid electrolyte interface (SEI) layer formation in Li secondary batteries. The electrochemical characteristics of the SEI layer were examined using chronopotentiometry (CP) and impedance spectroscopy. The Li₂CO₃-SEI layer prevents electrolyte decomposition reaction and has low interface resistance. In addition, the lithium ion diffusion in the SEI layer of the uncoated and the Li₂CO₃-coated electrode was evaluated using chronoamperometry (CA).     

Polyethylene-supported poly(acrylonitrile-co-methyl methacrylate)/nano-Al2O3 microporous composite polymer electrolyte for lithium ion battery

Nano-Al₂O₃ was doped in poly(acrylonitrile-co-methyl methacrylate) (P(AN-co-MMA)), and polyethylene(PE)-supported P(AN-co-MMA)/nano-Al₂O₃ microporous composite polymer electrolyte (MCPE) was prepared. The performances of the prepared MCPE for lithium ion battery use, including ionic conductivity, electrochemical stability, interfacial compatibility, and cyclic stability, were studied by scanning electron spectroscopy, linear sweep voltammetry, and electrochemical impedance spectroscopy. It is found that the nano-Al₂O₃ significantly affects the MCPE performances. Compared to the MCPE without any nano-Al₂O₃, the MCPE with 10 wt.% nano-Al₂O₃ reaches its best performances. Its ionic conductivity is improved from 2.0 × 10⁻³ to 3.2 × 10⁻³ S cm⁻¹, its decomposition potential is enhanced from 5.5 to 5.7 V (vs Li/Li⁺), and its interfacial resistance on lithium is reduced from 520 to 160 Ω cm². Thus, the battery performance is improved.     

Ionic conductivity and interfacial stability of Li6PS5Cl–Li6.5La3Zr1.5Ta0.5O12 composite electrolyte

Solid electrolytes which possess excellent lithium-ion conductivity and chemical compatibility with electrode materials are necessary for the commercialization of all-solid-state lithium batteries. However, a single solid electrolyte meeting above requirements is difficult. Consequently, the composite electrolytes have attracted more attention. In this paper, Li₆PS₅Cl–xLi_6.5La₃Zr_1.5Ta_0.5O₁₂ (LLZTO) (x = 0, 2.5 wt%, 5 wt%, 10 wt%) composite electrolytes are prepared by a simple planetary grinding process. It has been found that adding an appropriate amount of LLZTO can increase the lithium-ion conductivity. At 30 °C, the lithium-ion conductivity increases from 2.6 × 10⁻⁴ S/cm (Li₆PS₅Cl) to 5.4 × 10⁻⁴ S/cm (Li₆PS₅Cl-5 wt% LLZTO). Besides, the addition of LLZTO to the Li₆PS₅Cl can influence the growth rate of the SEI. It has been shown that the SEI growth rate obeys a parabolic rate law, and the growth rates of Li₆PS₅Cl, Li₆PS₅Cl-2.5 wt% LLZTO, Li₆PS₅Cl-5 wt% LLZTO, and Li₆PS₅Cl-10 wt% LLZTO are 8.62, 3.53, 3.33, and 3.38 Ω/h^1/2 at 60 °C, respectively. In lithium plating and stripping experiment, the voltage of symmetrical Li/Li₆PS₅Cl/Li cell suddenly drops to 0 V after cycling 39 h at 0.103 mA/cm² (0.097 mAh/cm²). On the contrary, the Li/Li₆PS₅Cl–xLLZTO (x = 2.5 wt%, 5 wt%, 10 wt%)/Li symmetrical cell exhibits a stable voltage profile over 100 h at the same test conditions. The corresponding interfacial impedance of Li/Li₆PS₅Cl–xLLZTO (x = 2.5 wt%, 5 wt%, 10 wt%) remains stable after 10, 30, and 50 charge/discharge cycles.

     

CBNM - determination of Li in BCR reference materials RM 303 and RM 304 lyophilized serum by isotope dilution mass spectrometry (IDMS)

Summary Lithium was determined in two BCR Candidate Reference Materials 303 and 304 by Isotope Dilution Mass Spectrometry using the state-of-the-art performance of isotope-specific methods gained during previous certifications of ⁶LiF reference targets used for the determination of the neutron lifetime [1]. After reconstitution of the serum, four aliquots of each of the two candidate materials from four different bottles were spiked with a previously characterized enriched ⁶Li spike [2] which is now available as CBNM IRM-615 and has a certified ⁶Li/⁷ Li ratio of 21.78±0.12 and a certified lithium concentration of 4.001±0.028 mol/g solution. The serum aliquots were digested in an HNO₃/H₂O₂ mixture and after evaporation of the acid, the lithium was separated on a cation exchange column, eluted with 0.3 mol/L HCl and used as LiCl for mass spectrometric measurement on an NBS type thermal ionization mass spectrometer. Similarly an unknown sample BCR X, provided by BCR to check the performance of the certifying laboratories, was analyzed. In addition the chemical preparation method was controlled by assaying NBS (NIST) SRM 909. The chemical blank was determined by IDMS using ⁶Li enriched CBNM IRM-615. The measurements were corrected for isotopic fractionation using the Isotopic Reference Material CBNM IRM-016 chemically prepared in the same way as the samples. The CRM samples as well as the BCR X sample and the NBS SRM 909 were also analyzed for isotopic composition to verify whether they had indeed natural isotopic composition. The final results have an overall uncertainty of 1.2 and 1.5%, respectively. This overall uncertainty (on a 2s basis or an estimate thereof) takes into account all uncertainty contributions of statistical as well as of systematic nature (uncertainties on used reference materials, density and blank determinations). The final results compare favorably with the values proposed by BCR for certification, but have a smaller (better) uncertainty: CRM 303: (0.517 4±0.005 7) mmol/L, CRM 304: (0.987±0.014) mmol/L     

Polymer/colloid dual-phase electrolyte membrane for rechargeable lithium batteries

In this work, a polymer/ceramic phase-separation porous membrane is first prepared from polyvinyl alcohol–polyacrylonitrile water emulsion mixed with fumed nano-SiO₂ particles by the phase inversion method. This porous membrane is then wetted by a non-aqueous Li–salt liquid electrolyte to form the polymer/colloid dual-phase electrolyte membrane. Compared to the liquid electrolyte in conventional polyolefin separator, the obtained electrolyte membrane has superior properties in high ionic conductivity (1.9 mS?cm^?1 at 30 °C), high Li⁺ transference number (0.41), high electrochemical stability (extended up to 5.0 V versus Li⁺/Li on stainless steel electrode), and good interfacial stability with lithium metal. The test cell of Li/LiCoO₂ with the electrolyte membrane as separator also shows high-rate capability and excellent cycle performance. The polymer/colloid dual-phase electrolyte membrane shows promise for application in rechargeable lithium batteries.     

Ionic conduction of lithium for Perovskite-type compounds, Li x La(1− x )/3NbO3 and (Li0.25La0.25)1− x Sr0.5 x NbO3

Perovskite-type compounds, Li _x La_{(1− x )/3}NbO₃ and (Li_0.25La_0.25)_{1− x} Sr_{0.5 x} NbO₃ as lithium ionic conductors, were synthesized by a solid-state reaction. From powder X-ray diffraction, the solid solution ranges of the two compounds were determined to be 0≤x≤0.25 and 0≤x≤0.125, respectively. In the Li _x La_{(1− x )/3}NbO₃ system, the ionic conductivity of lithium at room temperature, σ₂₅, exhibited a maximum value of 4.7 × 10⁻⁵ S · cm⁻¹ at x = 0.10. However, because of the decrease in the lattice parameters with increasing Li concentration x˙, σ₂₅ of the samples decreased with increasing x from 0.10 to 0.25. Also, in the (Li_0.25La_0.25)_{1− x} Sr_{0.5 x} NbO₃ system, the lattice parameter increased with the increase of Sr concentration and the σ₂₅ achieved a maximum (7.3 × 10⁻⁵ S · cm⁻¹ at 25 °C) at x = 0.125. Received: 12 September 1997 / Accepted: 15 November 1997