Lithium Halides Research Articles

Acidic "Water-in-Salt" Electrolyte Enables a High-Energy Symmetric Supercapacitor Based on Titanium Carbide MXene.

Titanium carbide MXene, Ti3C2Tx, exhibits ultrahigh capacitance in acidic electrolytes at negative potentials yet poor stability at positive potentials, resulting in low-energy densities for Ti3C2Tx-based symmetric supercapacitors. Utilizing "water-in-salt" electrolytes has successfully expanded the stable operation potential window of MXenes. However, this advancement comes at the cost of sacrificing their high capacitance in acidic electrolytes. In this work, we report an acidic "water-in-salt" (AWIS) electrolyte composed of sulfuric acid and saturated lithium halide, which effectively doubled the energy density of the Ti3C2Tx-based symmetric supercapacitor compared to those with bare acidic electrolytes. Specifically, the AWIS electrolyte successfully expanded the voltage window of the symmetric device to 1.1 V. A high specific capacitance of 112.34 F g-1 (at 10 mV s-1) was obtained due to the presence of proton redox. As a result, the symmetric device achieved a high-energy density of 19.1 Wh kg-1 and a high capacitance retention of 96.3% after 10,000 cycles. This work demonstrates the importance of designing stable and redox-active electrolytes for high-energy MXene-based symmetric supercapacitors.

Evolution of Interfacial Electro-Chemo-Mechanics between Lithium Metal and Halide Solid Electrolyte

Evolution of Interfacial Electro-Chemo-Mechanics between Lithium Metal and Halide Solid Electrolyte

A Na-Li dual cation liquid metal battery with high electrode utilization and high cycling stability

Liquid metal batteries (LMBs) with Na anode exhibit the advantages of low-cost, high-safety, long-lifespan, and easy scale-up, making them promising for large-scale energy storage applications. However, the high solubility of Na and its sluggish kinetics in discharge products result in severe self-discharge and low cathode utilization, significantly hindering the development of Na-based LMBs. In this study, a stable Na-Li dual cation LMB with metal Sb cathode is designed based on the in-situ displacement reaction between Na and molten salts of lithium halides electrolyte. This design effectively suppresses the self-discharge of the battery, and the multistage discharge mechanism of the dual-cation system enhances cathode utilization. Moreover, the self-healing property of the Sb cathode protects the electrode against volume expansion and degradation, enhancing cycling performance. The Na-Li| LiCl-KCl-NaCl |Sb cell was constructed and operated at 485 °C. The battery retained 97.02 % of its capacity after 800 cycles at 0.6 C, with a decay rate of 0.00373 % per cycle. Furthermore, the battery achieves a cathode material utilization of 89 % at 0.6 C. These improvements effectively promote the development and application of LMBs.

Solid-State Lithium-Ion Superionic Electrolytes with Reduced Moisture Sensitivity

The remarkable safety and high energy density of solid-state batteries (SSBs) created significant advantages in the development of next-generation energy storage. The properties of these batteries are highly dependent on the characteristics of solid-state electrolytes (SSEs), making them a crucial material in the development of such batteries. Following diverse principles of material design, lithium halide SSEs, particularly Li3InCl6, open new opportunities in the development of SSBs due to their unique properties including broad electrochemical stability window, high lithium-ion conductivity, and excellent deformability. Through a mechano-thermal synthesis approach, Li3InCl6 demonstrates substantial ionic conductivity at room temperature. We studied the temperature-dependent behavior of Li3InCl6 by using in-situ/operando techniques such as XRD and XPS. However, its susceptibility to moisture poses a significant challenge for practical implementation in SSBs. To overcome this limitation, this research is focused on a novel solution: hafnium doping of Li3InCl6. Integrating hafnium into the Li3InCl6 structure results in a substantial improvement in electrochemical performance. The Li2.6In0.6Hf0.4Cl6 solid-state electrolyte not only showcases heightened ionic conductivity but also demonstrates improved resistance to moisture. The achieved ionic conductivity reaches approximately 1 mS cm-1, marking a significant 3.5-fold increase compared to Li3InCl6. Noteworthy is the fact that, after 5 hours of exposure to air with 15% humidity, the observed reduction in ionic conductivity for Li2.6In0.6Hf0.4Cl6 is 37%, a notably lower decrease compared to the 57% reduction seen in Li3InCl6.The efficacy of hafnium doping provides a crucial advancement in the field of solid-state electrolytes, promising a transformative impact on next-generation energy storage systems.

Investigation on crystallographic orientation dependent ion transportation in Li3YBr6 superionic conductor for lithium ion battery

Enhancing ionic conductivity in solid electrolytes poses a significant hurdle in advancing all-solid-state batteries. Researchers have explored a variety of materials and techniques to elevate ionic conductivity. Lithium halide-based materials are emerging as a promising option for solid electrolytes due to their capacity for rapid ion conduction and robust electrochemical stability. Various methods, including substitution strategies and defect chemistry, have been deployed to enhance ionic conductivity within lithium halide solid electrolytes. Ionic conductivity is intricately linked to the substructure of migrating ions; therefore, ionic conductivity can be significantly enhanced by the alteration of the substructure. This work focuses on the impact of crystallographic orientation on ionic conductivity. Halide superionic conductor of structure Li3YX6 (X = halogen) has been used for the study. First, the ion transport mechanism in Li3YBr6 (in the C2/c phase) crystal has been examined and sequentially the impact of the crystallographic orientation has been investigated by creating two surfaces of different crystal orientations of pristine Li3YBr6. Findings of the present work show that among two different crystal-oriented surfaces (010) and (100) the (010) crystal-oriented structure Li3YBr6 has remarkable room temperature ionic conductivity (11.8 mS/cm) which is nearly fourteen times higher than that of pristine Li3YBr6 crystal while (100) oriented structure shows a little increment in room temperature ionic conductivity. To examine the mechanism behind this exceptional ionic conductivity in different structures energy barriers along different migration pathways have been evaluated. For the determination of the energy barrier nudged elastic band simulation was carried out. The results demonstrate that the (010) crystal-oriented surface structure possesses the lowest energy barrier, at 0.16 eV, which is 0.10 eV lower than the (100) oriented structure and 0.19 eV less than pristine Li3YBr6 (C2/c). This reduced energy barrier in the (010) crystal-oriented structure can be attributed to the prevalence of the tetrahedron-to-tetrahedron migration pathway.

Описание и исследование химического взаимодействия в системе Li+,Na+||F-,Cl-,Вг

The use of melts in various fields of industry and scientific research is based on the study of the properties of melts and the chemical processes occurring in them. In modern engineering and technology, a significant number of processes are associated with the use of mixtures of lithium and sodium halides as mixtures that accumulate heat, as electrolytes for medium-temperature chemical current sources. Therefore, the interest in the study of systems involving such systems is continuously increasing. The paper calculates the thermal effects of exchange reactions and Gibbs energy in ternary reciprocal systems of a quaternary reciprocal system Li+,Na+||F-,Cl-,Br-, as well as for a mixture corresponding to the central point of the conversion line. The conversion line is obtained as a result of the intersection of unstable and stable triangles. In accordance with the calculation data, it is shown that the conversion lines in the skeleton of the compositions intersect at the conversion point K3 with the maximum thermal effect of the reaction equal to the sum of the thermal effects of the reactions (as well as the Gibbs energies) for mixtures corresponding to the conversion points K1 and K2.To confirm the stability of the LiF-NaCl-NaBr triangle linking the stable tetrahedron LiF-NaCl-NaBr-NaF and the stable pentatope LiF-LiCl-LiBr-NaCl-NaBr, the interaction of the initial powder mixture of 50 mol % NaF+25 mol.% LiCl+25 mol.% LiBr has been studied by thermogravimetry. The phase transition temperatures are assigned to the heating curve of the mixture. When heated at a rate of 20 K/min, the exothermic effect begins at 463 oC and ends at 504 оC. For a stable triangle, a melt crystallization scheme of the composition of the central point of the conversion line is shown. Stable crystallizing phases have been confirmed by X-ray phase analysis.

Anionic Effects on Concentrated Aqueous Lithium Ion Dynamics.

The dynamics, orientational anisotropy, diffusivity, viscosity, and density were measured for concentrated lithium salt solutions, including lithium chloride (LiCl), lithium bromide (LiBr), lithium nitrite (LiNO2), and lithium nitrate (LiNO3), with methyl thiocyanate as an infrared vibrational probe molecule, using two-dimensional infrared spectroscopy (2D IR), nuclear magnetic resonance (NMR) spectroscopy, and viscometry. The 2D IR, NMR, and viscosity results show that LiNO2 exhibits longer correlation times, lower diffusivity, and nearly 4 times greater viscosity compared to those of the other lithium salt solutions of the same concentration, suggesting that nitrite anions may strongly facilitate structure formation via strengthening water-ion network interactions, directly impacting bulk solution properties at sufficiently high concentrations. Additionally, the LiNO2 and LiNO3 solutions show significantly weakened chemical interactions between the lithium cations and the methyl thiocyanate when compared with those of the lithium halide salts.

Effects of Lithium Halides on Electrode-Electrolyte Bifunctional Materials for High-Capacity All-Solid-State Batteries.

All-solid-state batteries have attracted attention because of their high energy density, safety, and long cycle life. Sulfide active materials exhibit high capacities and enable an enhanced energy density in all-solid-state batteries. In this study, we synthesized electrode-electrolyte bifunctional materials in the system Li2S-V2S3-LiX (X = F, Cl, Br, or I) through a mechanochemical process. In addition, the effects of the addition of lithium halides on the electrochemical properties were investigated. All-solid-state batteries with the Li2S-V2S3-LiI electrode showed the highest capacity of 400 mAh g-1 among all the cells, even though their electronic and ionic conductivities were the same. From the point of view of the ionic conductivity and structure of the electrodes during cycling, it was clarified that a high reversible capacity was achieved not only by high ionic and electronic conductivities before cycling but also by maintaining the ionic conductivity even at the deep state of charge. Furthermore, high-loading all-solid-state cells were fabricated using the Li2S-V2S3-LiI materials with a mass loading of 37.3 mg cm-2, exhibiting a high areal capacity of approximately 11.5 mAh cm-2 at 60 °C and good cycle performance.

Superionic Conductivity Invoked by Enhanced Correlation Migration in Lithium Halides Solid Electrolytes

Superionic Conductivity Invoked by Enhanced Correlation Migration in Lithium Halides Solid Electrolytes

Configurational Disorder, Strong Anharmonicity, and Coupled Host Dynamics Lead to Superionic Transport in Li3YCl6 (LYC).

In superionic crystals, liquid-like ionic diffusivities often come hand-in-hand with ultra-low thermal conductivity and soft vibrational dynamics. However, generalized relationships between ion transport and vibrational dynamics remain elusive due to the diversity of superionic materials and complex underlying mechanisms. Here, the links between vibrational dynamics and ion transport in close-packed lithium halide ion conductor Li3YCl6 (LYC) are examined using a suite of atomistic first-principles methods. It is shown that configurational disorder, lattice anharmonicity, and coupled host-mobile ion vibrational dynamics together induce a transition to the superionic state. Statistical correlations between ionic hops and activation of the distribution of vibrational modes are found. However, typical phenomena associated with superionic conductors such as selective breakdown of zone-boundary soft phonons, or long wavelength transverse acoustic modes as in the 'phonon-liquid-electron crystal' concept, are not present. Instead, anharmonic zone-boundary modes aiding Li diffusion are found to broaden and soften selectively but persist across the superionic transition. These anharmonic modes couple Li ion motion with the vibrations of the flexible close-packed anion framework, which remains stable and facilitates ionic hopping. The results provide insights into how configurational disorder and soft-yet-resilient vibrational modes enable ionic hopping, particularly in 3D close-packedcrystals.

Designing lithium halide solid electrolytes

All-solid-state lithium batteries have attracted widespread attention for next-generation energy storage, potentially providing enhanced safety and cycling stability. The performance of such batteries relies on solid electrolyte materials; hence many structures/phases are being investigated with increasing compositional complexity. Among the various solid electrolytes, lithium halides show promising ionic conductivity and cathode compatibility, however, there are no effective guidelines when moving toward complex compositions that go beyond ab-initio modeling. Here, we show that ionic potential, the ratio of charge number and ion radius, can effectively capture the key interactions within halide materials, making it possible to guide the design of the representative crystal structures. This is demonstrated by the preparation of a family of complex layered halides that combine an enhanced conductivity with a favorable isometric morphology, induced by the high configurational entropy. This work provides insights into the characteristics of complex halide phases and presents a methodology for designing solid materials.

Na2.5Cr0.5Zr0.5Cl6: A New Halide-Based Fast Sodium-Ion Conductor.

All-solid-state batteries employing solid electrolytes (SEs) have received widespread attention due to their high safety. Recently, lithium halides are intensively investigated as promising SEs while their sodium counterparts are less studied. Herein, a new sodium-ion conductor with a chemical formula of Na2.5Cr0.5Zr0.5Cl6 is reported, which exhibits high room temperature ionic conductivity of 0.1 mScm-1 with low migration energy barrier of ≈0.41eV. Na2.5Cr0.5Zr0.5Cl6 has a Fm-3m structure with 41.67mol.% of cationic vacancies owing to the occupation of Cr (8.33mol.%) and Zr (8.33mol.%) ions at Na sites. Supercell calculations show that the lowest columbic energy configuration has Cr/Zr/V (where V is the vacancy) clusters in the structure. Nonetheless, the clusters have mixed effects on the sodium ion conduction pathway, based on the Bond Valence Energy Landscape calculation. A global 3D Na-ion transport percolation network can be revealed in the lowest energy supercell. Effective pathways are connected through the NaCl6 and VCl6 nodes. Besides, Raman spectroscopy and 23Na solid-state nuclear magnetic resonance spectroscopy further prove the tunable structure of the SEs with different Cr to Zr ratios. The optimization between the concentration of Na+ and vacancies is crucial to create an improved network of Na+ diffusion channels.

In Situ/Operando Techniques for Unraveling Mechanisms of Ionic Transport in Solid-State Lithium Indium Halide Electrolyte

Over the past years, lithium-ion solid-state batteries have demonstrated significant advancements regarding such properties as safety, long-term endurance, and energy density. Solid-state electrolytes based on lithium halides offer new opportunities due to their unique features such as a broad electrochemical stability window, high lithium-ion conductivity, and elasticity at close to melting point temperatures that could enhance lithium-ion transport at interfaces. A comparative study of lithium indium halide (Li3InCl6) electrolytes synthesized through a mechano-thermal method with varying optimization parameters revealed a significant effect of temperature and pressure on lithium-ion transport. An analysis of Electrochemical Impedance Spectroscopy (EIS) data within the temperature range of 25–100 °C revealed that the optimized Li3InCl6 electrolyte reveals high ionic conductivity, reaching 1.0 mS cm−1 at room temperature. Herein, we present the utilization of in situ/operando X-ray Photoelectron Spectroscopy (XPS) and in situ X-ray powder diffraction (XRD) to investigate the temperature-dependent behavior of the Li3InCl6 electrolyte. Confirmed by these methods, significant changes in the Li3InCl6 ionic conductivity at 70 °C were observed due to phase transformation. The observed behavior provides critical information for practical applications of the Li3InCl6 solid-state electrolyte in a broad temperature range, contributing to the enhancement of lithium-ion solid-state batteries through their improved morphology, chemical interactions, and structural integrity.

Structural regulation of halide superionic conductors for all-solid-state lithium batteries

Metal halide solid-state electrolytes have gained widespread attention due to their high ionic conductivities, wide electrochemical stability windows, and good compatibility with oxide cathode materials. The exploration of highly ionic conductive halide electrolytes is actively ongoing. Thus, understanding the relationship between composition and crystal structure can be a critical guide for designing better halide electrolytes, which still remains obscure for reliable prediction. Here we show that the cationic polarization factor, which describes the geometric and ionic conditions, is effective in predicting the stacking structure of halide electrolytes formation. By supplementing this principle with rational design and preparation of more than 10 lithium halide electrolytes with high conductivity over 10−3 S cm−1 at 25 °C, we establish that there should be a variety of promising halide electrolytes that have yet to be discovered and developed. This methodology may enable the systematic screening of various potential halide electrolytes and demonstrate an approach to the design of halide electrolytes with superionic conductivity beyond the structure and stability predictions.

The correlation of the liquidus curves and valence electron structures of a ternary lithium halide molten-salt electrolyte for liquid metal batteries.

Liquid metal batteries have received considerable attention owing to their excellent properties. However, an electrolyte with low melting temperature is required to decrease operating temperature for the safety of liquid metal batteries and for saving energy. For revealing the mechanism of low liquefaction temperature, an empirical electron theory of solid molecules was used to study the thermal properties of pure lithium halides and their ternary-phase systems systematically. The theoretical bond lengths, melting points, liquefaction temperatures and mixed energies of pure lithium halides and their ternary phases match the experimental values well. The mechanism of liquefaction temperature for ternary lithium halides depends on their valence electron structures. The liquefaction temperature can be stabilized on a liquidus line or curve through the modulation of the constant number of covalent electrons (nc) and lattice electrons (nl). The liquefaction temperatures on various liquidus lines and curves are positively related to the linear density of valence electron pairs on the strong Li-X bond, bonding factor, and number of valence electrons in the s orbital but are negatively related to the number of valence electrons in the p orbital. With an increase in the linear density of the valence electron pair number and bonding factor, bond strength is enhanced, which increases the resistance of the strong Li-X bond against the break force induced by thermal phonon vibrations, and more thermal phonons with high vibrating energy are required for breaking the strongest Li-X bond at a higher temperature; therefore, the liquefaction temperature increases.

Morphology of Lithium Halides in Tetrahydrofuran from Molecular Dynamics with Machine Learning Potentials

The preferred structures of lithium halides (LiX, with X = Cl, Br, I) in organic solvents have been the subject of a wide scientific debate, and a large variety of...

Lithium chloride selective ion-pair recognition by heteroditopic [2]rotaxanes.

The first heteroditopic [2]rotaxane host systems capable of strong and selective binding of lithium chloride ion-pair species are described. Importantly, a cooperative 'switch on' mechanism was found to operate, in which complexation of a lithium metal cation enhances the halide anion affinity of the rotaxanes via a combination of favourable proximal electrostatic and preorganised allosteric effects. The mechanically bonded rotaxane host design features a macrocycle component possessing a 2,6-dialkoxy pyridyl cation binding motif and an isophthalamide anion binding group, as well as an axle component functionalised with either a halogen bonding (XB) iodotriazole or hydrogen bonding (HB) prototriazole moiety. Extensive quantitative 1H NMR titration studies in CD3CN/CDCl3 solvent mixtures determined enhanced ion-pair binding affinities for lithium halides over the corresponding sodium or potassium halide salts, with the axle prototriazole-containing HB rotaxane in particular demonstrating a marked selectivity for lithium chloride. Solid-state X-ray crystallographic studies and computational DFT investigations provide evidence for a [2]rotaxane host axle-separated ion-pair binding mode, in which complementary cation and anion binding motifs from both the macrocycle and axle components act convergently to recognise each of the charged guest species.

Forming Artificial Solid-Electrolyte-Interfaces between Lithium Metal Anodes and Halide and Sulfide Solid Electrolytes in All-Solid-State-Batteries Via Spatial-Atomic-Layer-Deposition

Increasing need in energy density and safety of current lithium-ion batteries has resulted in a search for next generation battery technologies1,2. All-solid-state-batteries (ASSBs) could answer these needs owing to the use electrode materials with higher capacities and potential difference, and by replacing flammable liquid electrolytes with solid electrolytes3,4. ASSBs using inorganic sulfide and halide solid electrolytes in particular have drawn a lot of attention as the electrolytes have very high RT ionic conductivities (>10-3 S.cm-1)5–7. Nevertheless, they suffer from issues related to electro-chemical and chemo-mechanical stabilities at electrode – electrolyte interfaces7,8. One promising approach to mitigate this issue is depositing an artificial solid-electrolyte-interface (SEI) layer via atomic-layer-deposition (ALD)9–11. In this work, we deposited a variety of artificial layers with different thicknesses and chemistries on the lithium metal anode using spatial ALD. We characterized the bonding within the thin film layer using X-ray photoelectron spectroscopy, and evaluated the stabilizing effect of the artificial SEI layer using electrochemical impedance spectroscopy and galvanostatic lithium plating and stripping methods. We compared the growth of lithium dendrites within the solid electrolyte pellets post-mortem analysis via scanning electron microscopy. J. Janek and W. G. Zeier, Nat. Energy (2023) https://www.nature.com/articles/s41560-023-01208-9.Q. Wang, L. Jiang, Y. Yu, and J. Sun, Nano Energy, 55, 93–114 (2019) https://doi.org/10.1016/j.nanoen.2018.10.035.J. B. Goodenough and M. H. Braga, Dalt. Trans. (2017) http://xlink.rsc.org/?DOI=C7DT03026F.J. Janek and W. G. Zeier, Nat. Energy, 1, 16141 (2016) http://www.nature.com/articles/nenergy2016141.R. Schlem et al., Adv. Energy Mater., 11, 2101022 (2021) https://onlinelibrary.wiley.com/doi/10.1002/aenm.202101022.S. Ohno et al., Prog. Energy, 2, 022001 (2020) https://iopscience.iop.org/article/10.1088/2516-1083/ab73dd.T. Koç, F. Marchini, G. Rousse, R. Dugas, and J. M. Tarascon, ACS Appl. Energy Mater., 4, 13575–13585 (2021).Y. He, C. Lu, S. Liu, W. Zheng, and J. Luo, Adv. Energy Mater., 9, 1–40 (2019).L. Han, C. Te Hsieh, B. Chandra Mallick, J. Li, and Y. Ashraf Gandomi, Nanoscale Adv., 3, 2728–2740 (2021).J. Liu and X. Sun, Nanotechnology, 26, 24001 (2015) http://dx.doi.org/10.1088/0957-4484/26/2/024001.Y. Jiang et al., Energy Storage Mater., 28, 17–26 (2020) https://doi.org/10.1016/j.ensm.2020.01.019.

Transforming Li3PS4 Via Halide Incorporation: a Path to Improved Ionic Conductivity and Stability in All‐Solid‐State Batteries

AbstractTo enhance Li+ transport in all‐solid‐state batteries (ASSBs), harnessing localized nanoscale disorder can be instrumental, especially in sulfide‐based solid electrolytes (SEs). In this investigation, the transformation of the model SE, Li3PS4, is delved into via the introduction of LiBr. 31P nuclear magnetic resonance (NMR)unveils the emergence of a glassy PS43− network interspersed with Br−. 6Li NMR corroborates swift Li+ migration between PS43− and Br−, with increased Li+ mobility indicated by NMR relaxation measurements. A more than fourfold enhancement in ionic conductivity is observed upon LiBr incorporation into Li3PS4. Moreover, a notable decrease in activation energy underscores the pivotal role of Br− incorporation within the anionic lattice, effectively reducing the energy barrier for ion conduction and transitioning Li+ transport dimensionality from 2D to 3D. The compatibility of Li3PS4 with Li metal is improved through LiBr incorporation, alongside an increase in critical current density from 0.34 to 0.50 mA cm−2, while preserving the electrochemical stability window. ASSBs with 3Li3PS4:LiBr as the SE showcase robust high‐rate and long‐term cycling performance. These findings collectively indicate the potential of lithium halide incorporation as a promising avenue to enhance the ionic conductivity and stability of SEs.

Exploring the effect of lithium halide artificial SEI on the electrochemical performance of lithium metal batteries

The urgent need for high-energy–density rechargeable batteries is driving lithium (Li) metal as a promising anode material. However, the conventional solid electrolyte interface (SEI) on lithium metal suffers from elevated interfacial impedance, poor mechanical properties, and non-uniform Li+ flux. Previously, LiF has been proven to be an effective component of the SEI protecting lithium metal. However, this is a rarely reported application of LiCl and LiBr in SEI. Herein, we design SEI containing lithium halide in different ratios (LiF0.8Cl0.1Br0.1, LiF0.33Cl0.33Br0.33, LiCl, LiBr) to investigate the action laws of lithium halide in SEI. It has been shown that the performance of SEI containing lithium halide against lithium anode increases with the LiF content in the SEI. The higher the proportion of LiF in SEI, the better the cycle life and stability of Li-Li symmetric cells, and the higher the initial capacity and the capacity retention of LFP-Li full cells. The symmetric cell with LiF0.8Cl0.1Br0.1@Li has the smallest average polarization voltage (about ± 30 mV) and long cycle life of up to 1000 h. LiFePO4||LiF0.8Cl0.1Br0.1@Li cells have the highest initial capacity (127.4 mAh/g), and still had 83.6 % capacity retention after 1000 cycles at 2C.