Growth of noncongruent LiTaO3 crystal by chemical vapor phase equilibration using niobium‐based two‐phase powder

Noncongruent nearly stoichiometric/lithium‐deficient LiTaO₃ crystal was grown by lithium‐rich/lithium‐deficient chemical vapor‐phase‐equilibration (VPE) technique, and low‐cost two‐phase powder LiNbO₃‐Li₃NbO₄ or LiNbO₃‐LiNb₃O₈ instead of expensive LiTaO₃‐Li₃TaO₄ or LiTaO₃‐LiTa₃O₈ was used in the VPE experiments. The LiTaO₃ crystalline phase in the lithium‐rich/lithium‐deficient crystal was confirmed by X‐ray analysis. The lithium‐rich/lithium‐deficient VPE‐induced lithium‐oxide (Li₂O) molar content increase/reduction was measured as a function of VPE duration using gravimetric method, and empirical relations between them are presented for both cases. We show that both the lithium‐rich and lithium‐deficient VPE techniques based on the two‐phase powder LiNbO₃‐Li₃NbO₄ or LiNbO₃‐LiNb₃O₈ can be successfully used to adjust the lithium‐oxide content in a LiTaO₃ crystal and produce a noncongruent nearly stoichiometric or lithium‐deficient crystal plate with desired lithium‐oxide content.     

Effect of surface modification using various acids on electrodeposition of lithium

Sulface modification of lithium was carried out using the chemical reaction of the native film with acids (HF, H₃PO₄, HI, HCl) dissolved in propylene carbonate (PC). The chemical composition change of the lithium surface was detected using X-ray photoelectron spectroscopy. The electrodeposition of lithium on the as-received lithium or the modified lithium was conducted in PC containing 1.0 mol dm^–3 LiClO₄ or LiPF₆ under galvanostatic conditions. The morphology of electrodeposited lithium particles was observed with scanning electron microscopy. The lithium dendrites were observed when lithium was deposited on the as-received lithium in both electrolytes. Moreover the dendrites were also formed on the lithium surface modified with H₃PO₄, HI, or HCl. On the other hand, spherical lithium particles were produced, when lithium was electrodeposited in PC containing 1.0 mol dm^–3 LiPF₆ on the lithium surface modified with HE However spherical lithium particles were not obtained, when PC containing 1.0 mol dm^–3 LiClO₄ was used as the electrolyte. The lithium surface modified by H₃PO₄, HI, or HCl was covered with a thick film consisting of Li₃PO₄, Li₂CO₃, LiOH, or Li₂O. The lithium surface modified with HF was covered with a thin bilayer structure film consisting of LiF and Li₂O. These results clearly show that the surface film having the thin bilayer structure (LiF and Li₂O) and the use of PC containing 1.0 mol dm^–3 LiPF₆ enhance the suppression of dendrite formation of lithium.     

Electrolytic deposition of lithium from non-aqueous solutions

This paper describes a study of the deposition of lithium from lithium salts (LiNO₃, LiCl, and LiClO₄) in organic solvents (CH₃CN, (CH₃)₂SO, HCONH₂, HCON(CH₃)₂, CH₃CON(CH₃)₂, and THF) using the potential-sweep technique. The current efficiency for lithium deposition was found to depend on both the solvent used and the particular anion in the electrolyte. In CH₃CON(CH₃)₂, (CH₃)₂SO, and HCON(CH₃)₂ solutions, the current efficiency for lithium deposition increased in the order: lithium chloride < lithium perchlorate < lithium nitrate whereas in CH₃CN it increased on addition of chloride. Addition of water to the LiNO₃-DMF solution also increased the current efficiency for lithium deposition. The solution which gave the highest efficiency was LiNO₃ in CH₃CON(CH₃)₂, in which efficiencies higher than 70% were obtained. The lithium metal deposited electrolytically from the LiNO₃-HCON(CH₃)₂ solution consisted of fine grains and had a high degree of crystallinity with very smooth deposit surfaces.     

Effect of vinylene carbonate as additive to electrolyte for lithium metal anode

The cycling efficiencies and cycling performance of a lithium metal anode in a vinylene carbonate (VC)-containing electrolyte were evaluated using Li/Ni and LiCoO₂/Li coin type cells. The cycling efficiencies of deposited lithium on a nickel substrate in an EC + DMC (1:1) electrolyte containing LiPF₆, LiBF₄, LiN(SO₂CF₃)₂ (LiTFSI), or LiN(SO₂C₂F₅) (LiBETI) at 25 and 50 °C were improved by presence of VC. However, the lithium cycling efficiencies at low temperature (0 °C) decreased by adding VC to the EC+DMC (1:1) electrolyte. The deposited lithium at low temperature exhibited a dendritic morphology and a thicker surface film. The lithium ion conductivity of the VC derived surface film was lower than that of the VC-free surface film at low temperature. Therefore, we concluded that the cycling efficiency decreased with decreasing temperature. On the other hand, the cell containing VC additive has excellent performance at elevated temperature. The deposited lithium at 50 °C in the VC-containing electrolyte exhibited a particulate morphology and formed a thinner surface film. The VC derived surface film, which consists of polymeric species, suppressed the deleterious reaction between the deposited lithium and the electrolyte.     

Characterization of structure and electrochemical properties of lithium manganese oxides for lithium secondary batteries hydrothermally synthesized from δ-KxMnO2

Lithium manganese oxides have attracted much attention as cathode materials for lithium secondary batteries in view of their high capacity and low toxicity. In this study, layered manganese oxide (δ-K_xMnO₂) has been synthesized by thermal decomposition of KMnO₄, and four lithium manganese oxide phases have been synthesized for the first time by mild hydrothermal reactions of this material with different lithium compounds. The lithium manganese oxides were characterized by powder X-ray diffraction (XRD), inductively coupled plasma emission (ICPE) spectroscopy, and chemical redox titration. The four materials obtained are rock salt structure Li₂MnO₃, hollandite (BaMn₈O₁₆) structure α-MnO₂, spinel structure LiMn₂O₄, and birnessite structure Li_xMnO₂. Their electrochemical properties used as cathode material for secondary lithium batteries have been investigated. Of the four lithium manganese oxides, birnessite structure Li_xMnO₂ demonstrated the most stable cycling behavior with high Coulombic efficiency. Its reversible capacity reaches 155 mAh g⁻¹, indicating that it is a viable cathode material for lithium secondary batteries.     

Recovery of Lithium from Seawater Using a New Type of Ion-Sieve Adsorbent Based on MgMn2O4

Abstract

A new type of ion-sieve manganese oxide, HMnO(Mg), was prepared by an acid treatment of MgMn₂O₄. The HMnO(Mg) showed a remarkably high selectivity for lithium ions among alkali metal and alkaline earth metal ions. The selectivity sequences were Na ? K ? Li for alkali metal ions and Mg ≤ Ca ≤ Sr ≤ Ba for alkaline earth metal ions at pH 8. The HMnO(Mg) showed a high selectivity for lithium ions in seawater. The lithium uptake increased with increasing solution pH and adsorption temperature. The maximum lithium uptake from native seawater reached 8.5 mg/g, corresponding to a lithium content of 1.8% in the form of Li₂O. The adsorbed lithium could easily be eluted with a dilute acid solution. The adsorptive capacity for lithium ions gradually decreased through repeated adsorption/elution cycles. The HMnO(Mg) after 4 cycles showed a lithium adsorptivity which was about 60% of the initial value.     

Influence of precursors of Li2O and MgO on surface and catalytic properties of Li‐promoted MgO in oxidative coupling of methane

The influence of the catalyst precursors (for Li₂O and MgO) used in the preparation of Li‐doped MgO (Li/Mg = 0.1) on its surface properties (viz basicity, CO₂ content and surface area) and activity/selectivity in the oxidative coupling of methane (OCM) process at 650–750 °C (CH₄/O₂ feed ratio = 3.0–8.0 and space velocity = 5140–20550 cm³ g⁻¹ h⁻¹) has been investigated. The surface and catalytic properties are found to be strongly affected by the precursor for Li₂O (viz lithium nitrate, lithium ethanoate and lithium carbonate) and MgO (viz magnesium nitrate, magnesium hydroxide prepared by different methods, magnesium carbonate, magnesium oxide and magnesium ethanoate). Among the Li–MgO (Li/MgO = 0.1) catalysts, the Li–MgO catalyst prepared using lithium carbonate and magnesium hydroxide (prepared by the precipitation from magnesium sulfate by ammonia solution) and lithium ethanoate and magnesium acetate shows high surface area and basicity, respectively. The catalysts prepared using lithium ethanoate and magnesium ethanoate, and lithium nitrate and magnesium nitrate have very high and almost no CO₂ contents, respectively. The catalysts prepared using lithium ethanoate or carbonate as precursor for Li₂O, and magnesium carbonate or ethanoate, as precursor for MgO, showed a good and comparable performance in the OCM process. The performance of the other catalysts was inferior. No direct relationship between the basicity of Li‐doped MgO or surface area and its catalytic activity/selectivity in the OCM process was, however, observed. © 2000 Society of Chemical Industry     

Effect of purification of 2-methyltetrahydrofuran/ethylene carbonate mixed solvent electrolytes on cyclability of lithium metal anodes for rechargeable cells

The effects of the purification of LiAsF₆–2-methyl tetrahydrofuran (2MeTHF)/ethylene carbonate (EC) mixed solvent organic electrolytes on the charge–discharge cyclability of lithium metal anodes has been investigated by using an accelerated method for evaluating lithium cycling efficiency. This method involves cycle tests on coin cells with an amorphous V₂O₅–P₂O₅ (95:5 molar ratio) cathode and an anode containing a small amount of lithium. Using this method, the cycle life of the cell was determined over a short period simply from the lithium cycling efficiency. The lithium cycling efficiency in LiAsF₆–2MeTHF/EC was improved by removing both water and organic impurities such as peroxides. An electrolyte containing less than 14ppm of water and 20ppm of organic impurities had a high lithium cycling efficiency of 97.2%.     

LiAlO2-coated LiNi0.8Co0.1Mn0.1O2 and chlorine-rich argyrodite enabling high-performance all-solid-state lithium batteries at suitable stack pressure

All-solid-state lithium batteries (ASSLBs), which are consisted of Li_5.5PS_4.5Cl_1.5 electrolyte, metal lithium anode and LiNi_0.8Mn_0.1Co_0.1O₂ (NCM811) cathode, are speculated as a promising next generation energy storage system. However, the unstable oxide cathode/sulfide-based electrolyte interface and the dendrite formation in sulfide electrolyte using the lithium metal anode hinder severely commercialization of the ASSLBs. In this work, the dendrite formation in sulfide electrolyte is investigated in lithium symmetric cell by varying the stack pressure (3, 6, 12, 24 MPa) during uniaxial pressing, and uniformly nanosized LiAlO₂ buffer layer was carefully coated on NCM811 electrode (LiAlO₂@NCM811) to improve the cathode/electrolyte interface stability. The result shows that lithium symmetrical cell has a steady voltage evolution over 400 h under 6 MPa stacking pressure, and the assembled LiAlO₂@NCM811/Li_5.5PS_4.5Cl_1.5/Li battery under the stack pressure of 6 MPa exhibits large initial discharge specific capacity and excellent cycling stability at 0.05 C and 25 °C. The feasibility of using the lithium metal anode in all-solid-state batteries (ASSBs) under suitable stack pressure combined with uniformly nanosized LiAlO₂ buffer layer coated on NCM811 electrode supply a facile and effective measures for constructing ASSLBs with high energy density and high safety.     

Effect of magnesium on the electrochemical behavior of lithium anode in LiOH aqueous solution used for lithium-water battery

The effect of adding magnesium to lithium on lithium electrochemical behavior in 4 mol L⁻¹ LiOH is studied using electrochemical techniques. The results show that the hydrogen evolution rate is decreased with increasing Mg content. Through theoretical analysis and X-ray (XRD) investigation, MgH₂ and Mg(OH)₂ are created on the surface film of lithium-magnesium alloys after discharge. The porosity of the lithium surface film is decreased by MgH₂, Mg(OH)₂ combined with LiOH and LiOH·H₂O and the hydrogen evolution rate is decreased effectively. Magnesium addition to lithium reduces the extent of hydrogen evolution by alteration of the hydride-hydroxide layer also reduces the extent of anodic dissolution without a significant change in the system efficiency.     

The conductivity and characterization of the plasticized polymer electrolyte based on the P(AN-co-GMA-IDA) copolymer with chelating group (II): The effect of free ion in the plasticized polymer electrolyte

A new gel-type polymer electrolyte (GPE) was made by the copolymerizing acrylonitrile (AN) and (2-methylacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester) (GMA-IDA). The copolymer mixed with a plasticizer—propylene carbonate (PC) and lithium salt to form GPE. The lithium salts are LiCF₃SO₃, LiBr and LiClO₄. FT-IR spectra show that the lithium ion in the LiClO₄ system has the strongest interaction with the group based on the plasticized polymer. FT-IR spectra also indicate that CF₃SO₃⁻ prefers producing anion-cation association. Moreover, the ¹³C solid state NMR spectra for the carbons attached to the PC of GPE exhibited different level of chemical shift (158.5 ppm) when the different lithium salts were added to the electrolyte. The results of differential scanning calorimeter (DSC) also indicate that the LiClO₄ system has more free lithium ions; therefore, it has the maximum conductivity. In this study, the highest conductivity 2.98 × 10⁻³ S cm⁻¹ exists in AG2/PC = 20/80 wt.% system which contain 3 mmole (g-polymer)⁻¹ LiClO₄. Additionally, the polymer electrolytes, which contain GMA-IDA have better interfacial resistance stability with lithium electrode.     

Electrochemical properties of lithium ionic conductors of the type: LiJ · xC9H15NO3 · CH3J

A series of lithium ionic conductors of the type: LiJ · xC₉H₁₅NO₃ · CH₃J (N-methylammonium iodide of 2,6,10-tri-oxa-13-azatricyclo[7,3,1,0^5,13]tridecane) was investigated. The ionic conductivity of these compounds is higher than that of pure lithium iodide and comparable to that of doped lithium iodide or lithium iodide alumina mixtures. This effect is obviously due to a softening of the substances at elevated temperatures. The electrochemicl properties were checked by cyclic voltammograms at elevated temperatures. Cells of the type Li/electrolyte/AgJ (mixt) and Le/electrolyte/J₂ were discharged and voltammograms of the AgJ (mixt) electrode were recorded.     

Effect of adding magnesium to lithium on the performance of discharge and hydrogen evolution of the lithium anode

The present study evaluates the effect of magnesium as an inhibitor on the performance of discharge and hydrogen evolution of lithium anode in alkaline electrolyte with additives. The electrochemical behaviors of lithium and lithium–magnesium alloy are assessed by hydrogen evolution rate, discharge current density, anodic potential, and potentiodynamic polarization. For these conditions, the results show that addition of magnesium to lithium enhances the current efficiency. Addition of 0.07 wt% Mg to lithium has minor effect on discharge current and anodic potential of lithium anode. The chemical composition and the morphology of the anode surfaces were evaluated by X-ray diffraction and scanning electron microscopy. The results show that the slow dissolution of lithium–magnesium alloy generates the formation of LiOH, LiOH·H₂O, and Mg(OH)₂. After discharge in saturated alkaline electrolyte with additives, the lithium–magnesium surface is less porous than lithium surface. Hydrogen evolution decrease, prompted by adding magnesium to lithium, is related to surface integrity enhanced by Mg(OH)₂.     

Examination of the effects of LiOH, LiCl, and LiNO3 on alkali-silica reaction

Lithium additives have been shown to reduce expansion associated with alkali-silica reaction (ASR), but the mechanism(s) by which they act have not been understood. The aim of this research is to assess the effectiveness of three lithium additives—LiOH, LiCl, and LiNO₃—at various dosages, with a broader goal of improving the understanding of the means by which lithium acts. The effect of lithium additives on ASR was assessed using mortar bar expansion testing and quantitative elemental analysis to measure changes in concentrations of solution phase species (Si, Na, Ca, and Li) in filtrates obtained at different times from slurries of silica gel and alkali solution. Results from mortar bar tests indicate that each of the lithium additives tested was effective in reducing expansion below an acceptable limit of 0.05% at 56 days. However, different lithium additive threshold dosages ([Li₂O]/[Na₂O_e]) were required to accomplish this reduction in expansion; these were found to be approximately 0.6 for LiOH, 0.8 for LiNO₃, and 0.9 for LiCl. Quantitative elemental analysis indicated that sodium and lithium were both bound in reaction products formed within the silica gel slurry. It is also believed that lithium may have been preferentially bound over sodium in at least one of the reaction products because a greater percent decrease in dissolved lithium than dissolved sodium was observed within the first 24 h. It appears that lithium additives either decreased silica dissolution, or promoted precipitation of silica-rich products (some of which may be nonexpansive), because the dissolved silica concentration decreased with increasing dosage of lithium nitrate or lithium chloride additive.     

Thermal behavior of the nonstoichiometric lithium niobate powders synthesized via a combustion method

Lithium niobate (Li_xNb_1?xO_3+δ) powders with various compositions are prepared via combustion synthesis. The thermal properties, crystal structure, and surface morphology of the as-prepared lithium niobate powders are characterized by thermogravimetric and differential thermal analyses (TG/DTA), powder X-ray diffraction (XRD), and scanning electron microscopy (SEM). When the calcination temperature reached 900 °C, the secondary phases Li₃NbO₄ and LiNb₃O₈ were observed. The lithium concentration before 900 °C was 40–43%. The lattice parameters increased slightly with decreasing concentration of lithium ions. When the calcination temperature was higher than 900 °C, the major Li_0.91NbO₃ phase and the minor LiNbO₃ phase coexisted in the nonstoichiometric lithium niobate with 43% lithium content.     

Lithium Ion Diffusion Mechanism in Lithium Lanthanum Titanate Solid‐State Electrolytes from Atomistic Simulations

Perovskite‐structured lithium lanthanum titanate (LLT, La_2/3–xLi_3xTiO_3, 0 <  x < 0.16) is a promising solid electrolyte with high lithium ion conductivity and a good model system to understand lithium ion diffusion behaviors in solids. Molecular dynamics (MD) and related atomistic computer simulations were used to study the diffusion behavior and diffusion mechanism as a function of composition in LLT solid‐state electrolytes. The effect of defect concentration on the structure and lithium ion diffusion behaviors in LLT was systematically studied using MD simulations and molecular static calculations with the goal to obtain fundamental understanding of the diffusion mechanism of lithium ions in these materials. The simulation results show that there exists an optimal vacancy concentration at around x = 0.067 at which lithium ions have the highest diffusion coefficient and the lowest diffusion energy barrier. The lowest energy barrier from dynamics simulations was found to be around 0.22 eV, which compared favorably with 0.19 eV from static nudged elastic band calculations. It was also found that lithium ions diffuse through bottleneck structures made of oxygen ions, which expand in dimension by 8%–10% when lithium ions pass through. By designing perovskite structures with larger bottleneck sizes can be a means of further improving lithium ion conductivities in these materials.     

Crystal structure of cubic Li7-3xGaxLa3Zr2O12 with space group of I-43d

Cubic Li_7-3xGa_xLa₃Zr₂O₁₂ is a cubic phase with a space group of I-43d instead of Ia-3d. This structure is more conducive to the migration of lithium ions. However, the effect of Ga on the size and environment of lithium ion transport channels has not been researched. In this work, Li_7-3xGa_xLa₃Zr₂O₁₂ (x = 0–0.25) was formulated, and the crystal structure was obtained by neutron diffraction. The results indicated that the minimum channel size to control Li⁺ migration in LLZO was the bottleneck size between the Li2 and Li3 sites (bottleneck size 2), and compared with lanthanum ions, the zirconium ions were closer to lithium ions. As the Ga content increased, bottleneck size 2 levelled off, while the lithium concentration and the distance between skeleton ions and lithium ions decreased. As a result, the lithium ionic conductivity primarily increased and then decreased. When doping 0.2 pfu of Ga, LLZO exhibited the highest lithium ionic conductivity of 1.45 mS/cm at 25 °C due to the coordinated regulation of Li⁺ concentration, bottleneck size, and the distance between skeleton ions and lithium ions.     

Gel electrolytes based on lithium modified silica nano-particles

In this work lithium modified silica (Li-SiO₂) nano-particles were synthesized and used as a single ion lithium conductor source in gel electrolytes. It was found that Li-SiO₂ exhibited good compatibility with DMSO, DMA/EC (a mixture of N,N-dimethyl acetamide and ethylene carbonate) and the ionic liquid, N-methyl-N-propyl pyrrolidinium bis(trifluoromethylsulfonyl) amide ([C₃mpyr][NTf₂]). Several gel electrolytes based on Li-SiO₂ were obtained. These gel electrolytes were investigated by DSC, solid state NMR, conductivity measurements and cyclic voltammetry. Conductivities as high as 10⁻³ S/cm at room temperature were observed in these nano-particle gel electrolytes. The results of electrochemical tests showed that some of these materials were promising for using as lithium conductive electrolytes in electrochemical devices, with high lithium cycling efficiency evident.     

Electrochemical behavior of anatase TiO2 in aqueous lithium hydroxide electrolyte

The electrochemical behavior of titanium dioxide (TiO₂) in aqueous lithium hydroxide (LiOH) electrolyte has been investigated. Cyclic voltammetry shows that electroreduction results in the formation of a number of products. X-ray diffraction of the electroreduced TiO₂ shows that Li _x TiO₂, Ti₂O₃, Ti₂O and TiO are formed. The formation of Li _x TiO₂ is confirmed through X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) studies of the electroreduced TiO₂. The formation of Li _x TiO₂ is electro reversible. In this respect, the electrochemical behavior of TiO₂ in concentrated aqueous lithium hydroxide electrolyte is similar to that for lithium perchlorate (LiClO₄) non-aqueous media.     

Isothermal calorimetry investigation of Li1+xMn2−yAlzO4 spinel

The heat generation of LiMn₂O₄, Li_1.156Mn_1.844O₄, and Li_1.06Mn_1.89Al_0.05O₄ spinel cathode materials in a half-cell system was investigated by isothermal micro-calorimetry (IMC). The heat variations of the Li/LiMn₂O₄ cell during charging were attributed to the LiMn₂O₄ phase transition and order/disorder changes. This heat variation was largely suppressed when the stoichiometric spinel was doped with excess lithium or lithium and aluminum. The calculated entropy change (dE/dT) from the IMC confirmed that the order/disorder change of LiMn₂O₄, which occurs in the middle of the charge, was largely suppressed with lithium or lithium and aluminum doping. The dE/dT values obtained did not agree between the charge and the discharge at room temperature (25 °C), which was attributed to cell self-discharge. This discrepancy was not observed at low temperature (10 °C). Differential scanning calorimeter (DSC) results showed that the fully charged spinel with lithium doping has better thermal stability.