Li Halides Research Articles

Tuning solvation behavior within electric double layer via halogenated MXene for reliable lithium metal batteries

Solid electrolyte interphase (SEI)/electrolyte interface is critical in determining the lithium (Li) plating/stripping behavior. The solvation structure of Li-ion is well understood in the bulk electrolyte. Still, the mechanism of how SEI components affect the Li-ion solvation structure and desolvation energy barrier at the SEI/electrolyte interface is still unclear. Herein, Ti3C2 Maxine with single halogenated terminations (−Cl, −Br, −I) are synthesized and used as a model system, because their surface terminations induce a double halide-rich SEI formation (LiF and LiCl/LiBr/LiI). We examine the influence of the interaction strength between different Li halides and Li-ion on coordination number of Li ions and distribution of Li ions within the inner Helmholtz plane (IHP). A solvation sheath with a low solvent coordination number forms near the IHP of the LiBr interphase, improving the kinetics of Li deposition. Accordingly, half-cells utilising Li-carbon fiber/Ti3C2Br2 electrodes exhibit a long lifespan of 12,000 h (1 mA cm−2, 1 mAh cm−2). A pouch cell comprising Li-carbon fiber/Ti3C2Br2 anode and LiFePO4 cathode displays a capacity retention rate of 97 % after 300 cycles even at a low negative to positive electrode capacity ratio of 2.26. Our research provides crucial principles for the design of SEI components in Li metal batteries.

Hybrid Artificial Solid Electrolyte Interphase with Dendrite-Free Lithium Deposition and High Ion Transport Kinetics.

Interfacial issues and dendritic Li deposition in lithium metal batteries (LMBs) hamper the practical application of liquid or solid-state cells. Here, a hybrid solid electrolyte interphase (SEI), based on hydroxyl-functionalized boron nitride (BN) nanosheets and poly(vinyl alcohol), is designed to solve the unstable nature of the Li anode-electrolyte interface. Rather than acquiring a rich Li halide environment through intense electrolyte decomposition, the hybrid SEI effectively regulates electrolyte decomposition and guarantees uniform Li plating via boosting interfacial Li+ ion transport at the interface. The Li+ ion boosting kinetics were deeply analyzed using simulations and spectroscopic analysis. It is revealed that the hydroxyl-functionalized BN can decrease kinetic energy barriers for Li+ ions and strongly holds TFSI- ions, thereby ensuring faster Li+ ion migration between electrodes and electrolytes. Tailoring the interfacial Li+ ion dynamics with hybrid SEI renders the Li transference number enhancement from 0.391 to 0.562 and 0.178 to 0.327 in liquid and solid-state cells, respectively. Moreover, Li symmetric cells with hybrid SEI exhibit an ultrahigh stability over 3500 h at 2 mA cm-2 with 2 mA h cm-2, along with the improved solid-state LMB performances. Our results suggest increasing Li+ ion transport at the interface is an alternative to resolve Li anode issues.

(Invited) Direct Recycling and Upcycling of Spent Ncm Cathodes through Flux-Mediated Synthesis

Ionic liquids (ILs) and molten salts (MSs) as flux media offer many advantages , such as negligible vapor pressures, negligible flammability, wide liquidus ranges, good thermal stability, and much synthesis flexibility. The unique solvation environment of these ionic media provides functional flux media for controlling topotactic formation of solid-state materials with a minimum perturbation of morphologies. A successful lithiation via ionothermal synthesis using a cost-effective Li halide as Li source and recyclable ILs as solvents will be discussed for the direct recycling of LiNi1/3Co1/3Mn1/3O2 (NCM 111) cathodes. The lithiation of spent cathodes can enable the direct recycling of spent cathode materials in lithium-ion batteries. In addition, the use of both ILs and MSs in upcycling spent NCM 111 will be also discussed.

Direct Recycling of Spent NCM Cathodes through Ionothermal Lithiation

AbstractIonic liquids (ILs) are a family of nonconventional molten salts that offer many advantages, such as negligible vapor pressures, negligible flammability, wide liquidus ranges, good thermal stability, and much synthesis flexibility. The unique solvation environment of these ILs provides new reaction or flux media for controlling formation of solid‐state materials with a minimum perturbation of morphologies. A successful lithiation via ionothermal synthesis using a cost‐effective Li halide as Li source and recyclable ILs as solvents is reported here for the direct recycling of LiNi1/3Co1/3Mn1/3O2 (NCM 111) cathodes. In addition, the ionic liquids can be readily recycled and reused after ionothermal lithiation. The lithiation of spent cathodes can enable the direct recycling of spent cathode materials in lithium‐ion batteries.

Fractionation of Cl/Br during fluid phase separation in magmatic–hydrothermal fluids

Brine and vapor inclusions were synthesized to study Cl/Br fractionation during magmatic–hydrothermal fluid phase separation at 900°C and pressures of 90, 120, and 150MPa in Li/Na/K halide salt–H2O systems. Laser ablation ICP-MS microanalysis of high-density brine inclusions show an elevated Cl/Br ratio compared to the coexisting low-density vapor inclusions. The degree of Cl/Br fractionation between vapor and brine is significantly dependent on the identity of the alkali metal in the system: stronger vapor partitioning of Br occurs in the Li halide–H2O system compared to the systems of K and Na halide–H2O. The effect of the identity of alkali-metals in the system is stronger compared to the effect of vapor–brine density contrast. We infer that competition between alkali-halide and alkali-OH complexes in high-temperature fluids might cause the Cl/Br fractionation, consistent with the observed molar imbalances of alkali metals compared to halides in the analyzed brine inclusions. Our experiments show that the identity of alkali metals controls the degrees of Cl/Br fractionation between the separating aqueous fluid phases at 900°C, and suggest that a significant variability in the Cl/Br ratios of magmatic fluids can arise in Li-rich systems.

Effect of Li-halides on the morphology of cuprates ceramics and their properties under neutron irradiation

Superconducting YBa2Cu3O7-d ceramics were prepared with small addition (2-10 mol%) of lithium halides (LiF and LiCl). In all cases, the sample structure became less compact but the grains got better connected. Therefore, there is an optimal content of Li halide, around 4 mol%, which provides the best transport properties and the highest critical temperature. When submitted to neutron irradiation, the normal state resistivity shows an overall increase while the critical temperature slightly increases (dTc ≤ 1 K) in the more homogeneous samples and decreases in the stronger Li-doped samples (dTc ≤ -2.8 K).

All-electron Bethe-Salpeter calculations for shallow-core x-ray absorption near-edge structures

X-ray absorption near-edge structure spectra are calculated by fully solving the electron/core-hole Bethe-Salpeter equation (BSE) in an all-electron framework. We study transitions from shallow core states, including the Mg ${L}_{2,3}$ edge in MgO, the Li $K$ edge in the Li halides LiF, LiCl, LiBr, and LiI, as well as ${\text{Li}}_{2}\text{O}$. We illustrate the advantage of the many-body approach over a core-hole supercell calculation. Both schemes lead to strongly bound excitons, but the nonlocal treatment of the electron-hole interaction in the BSE turns out to be crucial for an agreement with experiment.

Regularities in Melting Points of Lithium Halides: Is LiH Anomalous?

Using experimental data for the melting temperature T m for four Li halides (F to I), it is demonstrated that T m Z 1/3 is close to constant, ≅ (2530 ± 250) K, where Z is the atomic number of the halogen. This formula is not appropriate for what sometimes is considered the simplest halide, LiH, and therefore alternatives are investigated which involve a characteristic electrostatic energy e 2/εs, with s the internuclear separation and ε the static dielectric constant.

The Application of Atomic Force Microscopy for the Study of Li Deposition Processes

Li deposition on copper substrates was investigated using atomic force microscopy. The electrolyte solutions included , and solutions in propylene carbonate. This work demonstrated the applicability of atomic force microscopy to the study of Li electrochemistry. It proved that the sensitive electrodes and solutions can be properly isolated from atmospheric contaminants and that surface scanning of the tip leaves the electrode's morphology unchanged Li deposition in solutions was found to be more uniform than Li deposition in solutions. This difference is attributed to the different surface chemistry developed in the two electrolyte solutions as known from previous studies. It was also possible to follow surface film formation on copper upon polarization to potentials higher than those of Li deposition, due to reduction of solution species at low potentials and precipitation of insoluble Li halides, and .

Synthesis of LiMnO 2 and LiFeO 2 in molten Li halides

LiMnO 2 is obtained from NaMnO 2 via Li→Na exchange in molten LiI. The material crystallizes in an ordered rocksalt structure of idealized cationic distribution {Li 2} 16c [Mn 2] 16dO 4 (space group Fd3m). A second new method for the preparation of isotypic LiMnO 2 consists of Li intercalation via molten LiI into the spinel Li[Mn 2]O 4. LiFeO 2, with a layered ordered rocksalt structure of α-NaFeO 2 type (R 3 m) is obtained from NaFeO 2 via Li→Na exchange in an eutectic melt of LiCl and LiNO 3, whereas due to their higher melting points the employment of pure Li halides results in the formation of the α-LiFeO 2 type (Fm3m) with disordered rocksalt structure.

Correlation between surface chemistry, morphology, cycling efficiency and interfacial properties of Li electrodes in solutions containing different Li salts

The influence of the Li salt used on the behaviour of Li electrodes in tetrahydrofurane (THF) and propylene carbonate (PC) solutions was investigated. The salts studied included Li halides (LiBr, LiI), LiBF 4, LiPF 6, LiSO 3CF 3 and LiN(SO 2CF 3) 2. The correlation between the electrochemical properties, surface chemistry and morphology of Li electrodes in the above systems was studied using impedance spectroscopy, surface sensitive in situ and ex situ FTIR, X-ray microanalysis, electron microscopy and standard experiments of charge discharge cycling. It was found that all the salt anions explored have strong effects on all the above aspects, eg they strongly affect Li surface chemistry in solutions and participate in the build-up of surface films. The electrical properties of the Li-solution interphase formed in the different salt solutions are remarkably dependent on the salt anion. Consequently, the morphology and Li utility in repeated charge-discharge cycling are also strongly influenced by the salt used. Except for the Li halides, all the salts studied seem to be more reactive to lithium than LiClO 4 and LiAsF 6. They are worse than the commonly used LiAsF 6 for rechargeable Li battery systems because their strong involvement in the Li surface chemistry adversely affects Li cycling efficiency.

Polybutadiene Modification: Reactions of Halogen-Containing Polybutadienes with Organolithium Compounds

Abstract Polybutadiene (PB) can be easily halogenated by reaction with iodine chloride or bromine in tetrahydrofuran. The resulting glassy polymers were reacted with n-butyllithium, sec-butyl-lithium, and polystyryllithium in THF. Iodochlorinated PB gave a polybutadiene with a different cis/trans ratio with n-BuLi. The reformation of PB was accompanied by partial crosslinking. The reaction probably involved a halogen-metal exchange followed by intra- and intermolecular elimination of Li halide. With brominated PB, both coupling and elimination took place. With sec-BuLi, an allylic iodine derivative was obtained from iodochlorinated PB, probably by dehydrochlorination. The iodinated intermediate can easily undergo a coupling reaction with further sec-BuLi. Both iodochlorinated and brominated polybutadienes gave graft copolymers by reaction with polystyryllithium in THF. Grafting was always accompanied by gel formation.

Ultrasonic parameters in the born model of the lithium halides

The dC dP of the elastic constants of LiCl, LiBr and LiI have been measured at 295 K and are presented together with previous results for LiF. They are strikingly smooth when plotted against nearest neighbor distance, d 0, except for the longitudinal [110] stiffness of LiI. When combined with known temperature coefficients of the elastic constants, the dC dP lead to values of ξ = ( d ln B T dT ) v which are uniformly negative and smooth in the sequence FClBrI, but larger for these crystals of high Debye θ 295 than in the Na, K and Rb halides. The resulting Born model exponential parameters, d 0 ϱ , are precisely linear with d 0 in contrast with d 0 ϱ values where compression ξ were used in the necessary correction for vibrational effects. Values of dB T dP are all about 0·7 higher than predicted by the Born model for these materials with relatively low d 0 ϱ , but the trend with d 0 conforms to the prediction. In this respect, and in ξ, the Li halides are somewhat different than the Na. K and Rb halides but otherwise fit in well.

Stereoselektivität diastereogener CC‐Verknüpfungen, I. Die Beeinflußbarkeit der syn‐Stereoselektivität bei Carben‐Additionen an Olefine

AbstractDas Verhältnis, in dem diastereomere Cyclopropane gebildet werden, ist von mehreren Faktoren abhängig, insbesondere auch von der Olefin‐Konzentration. Vorsicht scheint deshalb geboten zu sein, wenn aus solchen Diastereomerenverhältnissen mechanistische Rückschlüsse gezogen werden sollen.

Optical Properties of Na and Li Halide Crystals at 55 °K

AbstractNew results on the low temperature reflectivity of Li and Na halides between 5 and 10 eV are reported and discussed on the basis of recent band structure calculations. Furthermore, fine structure accompanying the lowest exciton has been detected in some crystals. This structure is examined in detail and attributed to the exciton‐phonon interaction.

The energy of formation of Schottky defects in ionic crystals

Abstract This paper calculates the energy of formation Ws of Schottky defects in ionic crystals by methods derived from the original method of Mott and Littleton. The main aim of these calculations is to examine the variations in the predicted energies resulting from reasonable variations in the assumed models. The types of variation considered are: (1) changes in the description of the long-range displacement and polarization field around the vacancies, corresponding to the inclusion of (a) purely elastic distortions and (b) electronic deformations of the ions resulting from the polarization of the lattice; (2) changes in the magnitude of the second neighbour Born-Mayer interactions corresponding to different available choices for ionic radii and to the inclusion or otherwise of Van der Waals forces; and, more briefly, (3) changes from the Born-Mayer form to the Born—Mayer-Yerwey form of closed-shell repulsion potential. The results are given in tables but are broadly as follows. For a given closed-shell repulsive potential, the inclusion of elastic terms in the displacement field (in addition to polarization displacements resulting from the effective charges on the defects) raises Ws, while inclusion of electronic deformations lowers it again. The net result of including both is to increase Ws by ∼½ev. For given assumptions about the displacement and polarization field changes in the Born-Mayer constants can be important; thus use of the conventional Goldschmidt radii in place of the more recent radii of Tosi and Fumi leads to a lowering of the Schottky energies by amounts which are larger for the compounds of small cations and large anions—for NaCl by ∼1/2ev. These results are consistent with those of Tosi and result from the importance of the first-neighbour interactions in determining Ws. Use of a Born-Mayer—Yerwey potential increases Ws compared to the values for the corresponding Bom-Mayer form. Experimental values of W s are known for some alkali halides. Reasonable agreement with those for Nad, NaBr and KC1 results from using the Tosi-Fumi constants in a Born-Mayer potential, but for the Li halides and KBr the calculated values are too low. For these substances a somewhat stiffer potential seems necessary. Our results, especially those on the effect of the changes in the closod-shell repulsions, are important for the extension of this model to simple oxides.

Elastic Constants of the Alkali Halides at 4.2°K

Adiabatic elastic constants of LiCl, NaF, NaCl, NaBr, KF, RbCl, RbBr, and RbI were measured at 4.2 and 300\ifmmode^\circ\else\textdegree\fi{}K, using the ultrasonic pulse-echo technique. Data are also given for several of these materials, for the temperature interval 4.2 to 300\ifmmode^\circ\else\textdegree\fi{}K. It is observed that the elastic anisotropy factor, $A=\frac{2{c}_{44}}{({c}_{11}\ensuremath{-}{c}_{12})}$, increases with temperature. This results in the Li halides becoming less anisotropic and the Na, K, and Rb halides becoming more anisotropic as the temperature decreases toward $T=0\ifmmode^\circ\else\textdegree\fi{}$K. The Cauchy relation (${c}_{12}={c}_{44}$) is not satisfied at 4.2\ifmmode^\circ\else\textdegree\fi{}K for any of the materials studied. The degree of failure of the Cauchy relation ($\ensuremath{\Delta}={c}_{12}\ensuremath{-}{c}_{44}$) is larger at 4.2\ifmmode^\circ\else\textdegree\fi{}K than at room temperature for the Li and Na halides but is smaller for the K and Rb halides. Also calculated was the $T=0\ifmmode^\circ\else\textdegree\fi{}$K value ${{\ensuremath{\Theta}}_{0}}^{\mathrm{el}}$ of the Debye characteristic temperature from the 4.2\ifmmode^\circ\else\textdegree\fi{}K elastic-constant data, using the tables given by de Launay. The values of ${{\ensuremath{\Theta}}_{0}}^{\mathrm{el}}$ in \ifmmode^\circ\else\textdegree\fi{}K are: LiCl (429\ifmmode\pm\else\textpm\fi{}2.2), NaF(491.5\ifmmode\pm\else\textpm\fi{}2.4), NaCl(321.2\ifmmode\pm\else\textpm\fi{}1.6), NaBr(224.6\ifmmode\pm\else\textpm\fi{}1.2), KF(335.9\ifmmode\pm\else\textpm\fi{}1.7), RbCl(168.9\ifmmode\pm\else\textpm\fi{}0.85), RbBr(136.5\ifmmode\pm\else\textpm\fi{}0.7), and RbI(108.0\ifmmode\pm\else\textpm\fi{}0.55). Comparison with ${{\ensuremath{\Theta}}_{0}}^{c}$ the Debye characteristic temperature derived from low-temperature specific-heat data, shows the two to be equal within experimental error in almost all cases. However, there is some indication of a trend toward ${{\ensuremath{\Theta}}_{0}}^{\mathrm{el}}$ being larger than ${{\ensuremath{\Theta}}_{0}}^{c}$ by an amount on the order of 1 to 3%. Whether this trend is real or the result of some systematic error in the experiments or analysis is not known at this time.

The ionic conductivity of Li‐halide crystals

AbstractThe ionic conductivity of mixed crystals of Li halides and Mg halides has been measured. From these measurements the mobility of Li vacancies and the concentration of vacancies in pure Li halides has been derived, with the two assumptions that the defects in Li halides are Schottky defects and the mobility of halide vacancies is negligibly small.The conductivity can be represented by an equation of the form:x = A exp(‐U/kT)[1 + {1 + (4 A′/a2) exp(‐E/kT)}½]in which x is the specific conductivity, U the height of the potential barrier which must be surmounted by the Li+ ions when moving through the crystal, E the energy required for the formation of a pair of vacancies, a the concentration of Mg halide and A′ and A constants.The magnitude of E, U, A and A′ (table I) have been compared with theoretical estimates.