Li Atoms Research Articles

Efficient CO2 capture and separation in TpPa COFs: Synergies from functional groups and metal Li

Covalent organic frameworks (COFs) have emerged as promising materials for CO2 capture and separation owing to their exceptional structural stability. Herein, grand canonical Monte Carlo simulation (GCMC) and density functional theory (DFT) were used to first screen the most favorable functional group in the COFs consisting of 1,3,5-triformylphloroglucinol (Tp) and p-phenylenediamine (Pa) functionalized with –OH, –COOH, and –SO3H, respectively (TpPa-X). Subsequently, the H atoms of –SO3H, the best functional group, were replaced by Li atoms to form –SO3Li, revealing the synergies of functional group –SO3H and Li modification on selective CO2 capture. TpPa-OLi/COOLi were also constructed to confirmed the universality of this synergistic effect. The introduction of functional groups enhanced the CO2 capture and separation performances by creating a more suitable pore environment. The Li introduction increased the structural polarity and provided strong adsorption sites, further improving the selective CO2 capture performance. Notably, TpPa-SO3Li exhibited a remarkable CO2 adsorption capacity of 136.11 cm3 cm−3 with the CO2 over N2/CH4 selectivity of 264.22/164.38, respectively, at 298 K and 1.0 bar. Structural stabilities, pore characteristics, gas adsorption distribution, isothermal adsorption heat, and interactions were adopted to reveal the synergistic effect between functional groups and Li in enhancing CO2 capture and separation.

Centrosymmetric CaBaMF8 and Noncentrosymmetric Li2CaMF8 (M = Zr, Hf): Dimension Variation and Nonlinear Optical Activity Resulting from an Isovalent Cation Substitution-Oriented Design.

Zirconium/hafnium fluorides have recently been recognized as potential nonlinear optical (NLO) materials with short ultraviolet (UV) cutoff edges, which is significant in laser science and industry. The synthesis of noncentrosymmetric (NCS) materials based on centrosymmetric (CS) compounds by an isovalent cation substitution-oriented design is an emerging strategy in the NLO territory. Here, two isostructural and novel fluorides, CaBaMF8 (M = Zr (1), Hf (2)), have been synthesized through the combination of alkaline earth metals, zirconium/hafnium, and fluorine elements. They feature zero-dimensional and CS structures composed by an isolated MF8 (M = Zr, Hf) dodecahedron and dissociative Ca2+ and Ba2+ cations, and they display short UV cutoff edges (<200 nm) as well. Two three-dimensional fluorides Li2CaMF8 (M = Zr (3), Hf (4)) are obtained by replacing Ba with alkali metal Li atom, which not only represent phase-matchable second-harmonic-generation activities (0.36, 0.30× KH2PO4 (KDP)) at 1064 nm but also maintain short UV cutoff edges with high reflectance. This work has largely enriched the family of NCS zirconium/hafnium fluorides reaching the short UV region.

Lithium on CH Divacancy Self-Healed Graphane: A First-Principles Study

The possibility of using graphane monolayer crystals as an electrode material is becoming popular. Graphane is stable at room temperature and has a large surface area, but its chemical inertness hinders its direct interactions with Li ions. In this study, we performed density functional theory calculations to study the energetic stability and structural and electronic properties of Li on graphane with various CH divacancy configurations (v12, v13, and v14). The results show that the adsorption of the Li atom reduces the formation energy of the CH divacancy configurations. The Li-v12 is most stable with the highest binding energy of 3.25 eV/Li and relaxes to in-plane with other C atoms. Altering the Li charge state to have Li−1-v12 or Li+1-v12 affects the energetic stability and electronic characters of Li-v12. The Li−1-v12 (Li+1-v12) slightly (greatly) reduces the binding force between the Li and v12 configuration, and furthermore it improves (deteriorates) the conductivity of the structure. Further investigation of graphane with vacancies is encouraged due to these intriguing observations, as it holds promise for potential utilization as an electrode material.

Enabling fast diffusion/conversion kinetics by thiourea-induced wrinkled N, S co-doped functional MXene for lithium-sulfur battery

The long lifespan of high-energy density lithium-sulfur batteries (LSBs) is still hindered by severe polysulfide (PS) shuttling and sluggish sulfur reduction/evolution kinetics process. Herein, we report a facile preparation of thiourea-induced wrinkled nitrogen and sulfur co-doped functionalized MXene (NSMX) to modify the separator to enhance the ion diffusion and conversion kinetics for high-energy LSBs. The combination of theoretical calculations and experimental conclusions demonstrates that the introduction of N, S heteroatoms induces the shift of the d-band center in transition metal Ti towards the Fermi level and results in the robust bonding effect between N/S atoms and Li atom in PS, hence exhibiting admirable adsorption capability to PS and fast catalytic PS reversible conversion rate, which quickly deplete soluble high-order PS and expedites the depletion of the Li2S6 in high potential. The 2D wrinkled polar surface with excellent conductivity assures fast electron transfer and ion migration. Profiting from the enhancement of S utilization and the reduction of unfavorable accumulated Li2S6, the LSBs equipped with NSMX modified separators exhibit a high specific capacity of 1249 mAh g−1 at 0.2 C. At a high rate of 5 C, the LSBs also delivered an impressive reversible capacity of 600 mAh g−1. Moreover, a high capacity and stable cycling can be achieved even under the condition of high S load and lean electrolyte consumption.

Pushing The Extreme of Multicentre Bonding: Planar Pentacoordinate Hydride.

Planar hypercoordination has sparkled interest among the researchers from last few decades. Most of the elements in the Periodic Table have shown this remarkable structural feature. However, the smallest element, hydrogen, is missing in the list. No evidence is there in the literature. Herein, we introduce the first planar pentacoordinate hydrogen atom (ppH) in the global minimum geometry of Li5 H6 - cluster. Bonding analysis indicates that the central hydrogen atom is stabilized by multicentre bonding with five surrounding Li atoms. Natural charge analysis reveals that the central hydrogen is acting like a hydride which is strongly attracted by the positively charged surrounding lithium centres. The ppH structure is stabilized by strong electrostatic attraction as well as extensive multicentre bonding. Aromaticity has no role to play here. The cluster is dynamically stable and is expected to be detected in gas phase.

Pushing The Extreme of Multicentre Bonding: Planar Pentacoordinate Hydride

AbstractPlanar hypercoordination has sparkled interest among the researchers from last few decades. Most of the elements in the Periodic Table have shown this remarkable structural feature. However, the smallest element, hydrogen, is missing in the list. No evidence is there in the literature. Herein, we introduce the first planar pentacoordinate hydrogen atom (ppH) in the global minimum geometry of Li5H6− cluster. Bonding analysis indicates that the central hydrogen atom is stabilized by multicentre bonding with five surrounding Li atoms. Natural charge analysis reveals that the central hydrogen is acting like a hydride which is strongly attracted by the positively charged surrounding lithium centres. The ppH structure is stabilized by strong electrostatic attraction as well as extensive multicentre bonding. Aromaticity has no role to play here. The cluster is dynamically stable and is expected to be detected in gas phase.

The role of radiation pressure in lithium deficit for stars in the stage of late accretion: failure of lithium test for young stellar clusters

ABSTRACT We study the behaviour of lithium atoms in the radiation field of main-sequence (MS) stars. The radiation pressure on atoms in the resonant lines of the ${\rm Li\, {\small I}}$ 6708 Å doublet exceeds the gravity at Teff &amp;gt; 3000 K. The lifetime of ${\rm Li}$ atoms before their ionization is sufficient to achieve the escape velocity. Free ${\rm Li}$ atoms cannot approach the pre-main sequence (PMS) and MS stars if the surrounding gas is sufficiently transparent. Accretion of small bodies (SBs) can partially restore the lithium abundance when SB directly falls on to the star in elongated orbits. In the case of accretion from discs consisting of SB fragments, when the parent bodies move in quasi-circular orbits, the boundary of the SB sublimation region plays a decisive role. Near hot stars, the free ${\rm Li}$ atom is rapidly ionized and participates in accretion on to the star in the form of ions, contributing to an increase in the ${\rm Li}$ abundance. Low-mass stars with low temperatures cannot hold lithium atoms. Near stars with Planck energy distribution in the radiation field, lithium deficiency occurs if 3000 K &amp;lt; Teff &amp;lt; 3400 K. New stars with [Fe/H] = 0.0 may indicate a lithium deficiency at Teff &amp;lt; 5000 K. Failure of the lithium test to estimate the age of a stellar cluster may indicate a significant contribution of accretion in the form of debris discs consisting of SBs.

Li Decorated Penta-BCN as a Competitive Reversible Hydrogen Storage Media: A First-Principles Study.

Efficient storage media are crucial for practical applications of hydrogen, which is the most promising clean energy resource. In addition to possessing a highly reversible gravimetric capacity, the stability and superlight mass of potential storage media should not be underestimated. In this study, we exploit the light mass and unique puckered structure of penta-BCNs to design Li-decorated penta-BCNs for hydrogen storage via a series of first-principles calculations. Our results reveal that Li atoms can form stable chemical complexes with the surface of penta-BCNs with an average binding energy of -2.21 eV without causing deformation. Each Li@penta-BCN unit can physically adsorb up to 27H2 molecules, and the highest hydrogen storage capacity can reach 7.44 wt %, with an average adsorption energy of -0.16 eV/H2, surpassing the target value of 5.5 wt % set by the U.S. Department of Energy. Further elaborate analysis of the electronic structure shows the polarization enhancement mechanism, which is caused by charge transfer from Li atoms to the penta-BCN surface. Our results indicate that Li-decorated penta-BCN could be a promising hydrogen storage material for further application and inspire the theoretical or experimental design of novel materials for clean energy.

Modulating the Electrical Properties of Lithium-Doped Zinc Oxide: Interplay of Lithium Content, Oxygen Pressure, and Temperature

This research elucidates the intricate interplay of lithium content, oxygen pressure, and temperature and their influence on the electrical properties of Lithium-doped zinc oxide (LZO). The electrical behavior of zinc oxide (ZnO), a prominent semiconductor material, can be modulated when doped with lithium (Li). Through systematic experimentation, we demonstrate that varying lithium content in the ZnO matrix leads to notable shifts in carrier concentration and mobility, which in turn impacts the material's conductivity and overall electrical performance. Furthermore, oxygen pressure during synthesis plays a pivotal role in defect formation, especially oxygen vacancies, which interact dynamically with lithium dopants to further modulate electrical behavior. Introducing the variable of temperature, our study reveals a synergistic effect, where temperature not only affects intrinsic carrier concentration but also the interactions between lithium dopants and inherent defects in ZnO. Under optimized conditions of oxygen pressure and temperature, the influence of Li content on crystallinity was pronounced, consequently impacting mobility. In contrast, under unoptimized conditions, as Li concentration increased, particularly beyond optimal levels (0.75 mol%), introduced Li atoms assumed the role of compensating centers by capturing or neutralizing carriers, reducing mobility. The findings presented herein provide a comprehensive understanding of how these factors collectively determine the electrical properties of LZO, paving the way for tailored applications in optoelectronic devices, sensors, and more.

Interfacial structures and dissociation reactions of protic ionic liquids on Li metal surface: A combined first-principles and ab initio molecular dynamics investigation

Interfacial structures and dissociation reactions of protic ionic liquids (PILs) comprising five protic cations with two common sulfonylimide anions on the Li(001) surface were investigated using first-principles calculations and ab initio molecular dynamics simulations. Both the anions rapidly decompose, yielding LiF, Li2O and Li2S species as well as large fragments, e.g. NSO2CF3 and NSO2. Particularly, the proton attached to the N atom generally segregates from the cations and generates LiOH with the O atom from the anions and the surface Li atom. In addition, detailed comparisons of reaction mechanisms between PIL-based and AIL-based systems were also made.

Solid breeder material crystal structure evolution due to Li burn up–Loss of crystal stability

Solid breeder materials for fusion power plants are subjected to extreme conditions of radiation damage, high temperature and designed component burn-up. The loss of lattice stability of Li2TiO3 due to Li burn-up was investigated using first principles-based approaches to aid evaluation of upper limit of component lifetime. The lattice stability is analyzed using calculated phonon dispersion in the Li2TiO3 supercell, while Li burn-up is modeled by the introduction of Li-vacancies. It has been determined that the studied ceramic can be structurally stable up to ∼40% of Li atoms burn-up. At 50% burn-up, the negative frequency branch in the phonon dispersion spectrum appears indicating the loss of lattice dynamical stability. Moreover, the structure obtained by introduction of unstable frozen phonons with minima energy amplitude also results in a phonon dispersion with negative branches in the structure obtained. Therefore, the system completely loses stability when approximately half of Li atoms are consumed.

The interface effect on the lithiation of silicon/graphene composites: The first principles study

AbstractTo reveal the interaction mechanism between lithium (Li) and silicon/graphene (Si/Gra) interface at the atomic scale, it was calculated that the energy band structure, density of states, charge transfer, radial distribution function and Li diffusion coefficient based on the first principles. The results indicated that the volume expansion of Si was effectively limited by the Si/Gra interface during Li insertion. There appeared the interface effect of Si/Gra on the combination of Li and Si atoms, according to the longer Li‐C (2.9 Å) and the larger electron cloud near the Li atom at the Si/Gra interface. The better diffusion channel for Li atoms was constructed at the Si/Gra interface, due to the lower diffusion energy barrier (0.42–0.44 eV) and higher diffusion coefficient (DLi = 0.784 × 10−4 cm2/s) for Li+ diffusion.

Reduction of Irreversible Capacity in Lithium-ion Batteries

This article is focused on a research of negative materials for Lithium-ion batteries. In the research are considered methods, which can lead to enhance capacity of Lithium-ion batteries. The increase of the battery capacity is based on reduction of irreversible capacity. The majority of Li-ion batteries which are used in this time has negative electrode make from graphite. On interface between electrolyte and graphite electrode originates the SEI layer (Solid-Electrolyte Interphase), this layer is the cause of irreversible capacity of graphite. This layer is indispensable for appropriate battery function but for creating this layer is consumed almost one-third potential capacity of Li-ion cell. In our research we attempted to prepare the material which would reduce these capacity losses. Was designed a concept where n-butyllithium (C4H9Li) reagent behaves as the source of lithium atoms and graphite acts like acceptor of lithium atoms. This process is called „lithiation“, our conception presents n-butyllithium like oxidative reagent which is able to reduce graphite material by Li atoms. Lithium atoms are intercalated between graphite sheets (as at charging process), resulting of this process is new lithiated electrode material which can be used for prepare of negative electrode for Li-ion cells.

Rational construction Ag/LiF/sulfide rich protective layer for remarkably enhancing the stability of Li metal anodes

Li metal is a promising anode material for high-energy–density batteries due to its high theoretical capacity and low redox potential. However, both the uncontrolled Li dendrite growth and unstable solid electrolyte interphase (SEI) layer restricts its large-scale practical applications. Herein, an artificial protective layer consisting of Ag nanoparticles, lithium fluoride (LiF) and sulfide are innovatively designed and fabricated via the in-situ chemical reaction between Ag(I) trifluoromethylthiolate (AgSCF3) and Li metal. Density functional theory (DFT) results indicate that Ag nanoparticles have a high binding energy with Li atom and LiF/sulfide have wide band gap, which would provide plenty of nucleation sites for Li+ and reduce the direct contact between inner Li metal and the electrolyte. The co-existence of Ag and LiF/sulfide results in a strong synergistic effect, and this is confirmed by the systematical comparison with single modified Ag-Li and double modified F/S-Li anodes. Benefitting from this synergistic effect, the Ag/F/S-Li symmetrical cells can stably work for 2000 h with low-voltage hysteresis at current density of 1 mA cm−2. Full cells assembled with LiCoO2 (LCO) and LiFePO4 (LFP) cathodes displays much better long‐term cycle performance when the Ag/F/S-Li anode is applied. Furthermore, this Ag/F/S-Li modification can significantly enhance discharge capacity, rate performance, as well as energy density of Li(or LiB alloy)||MnO2 primary cells. This promising work promotes the practical application of Li metal and provides new insight into the protective layer design in stable Li metal batteries.

Direct bandgap emission from strain-doped germanium

Germanium (Ge) is an attractive material for Silicon (Si) compatible optoelectronics, but the nature of its indirect bandgap renders it an inefficient light emitter. Drawing inspiration from the significant expansion of Ge volume upon lithiation as a Lithium (Li) ion battery anode, here, we propose incorporating Li atoms into the Ge to cause lattice expansion to achieve the desired tensile strain for a transition from an indirect to a direct bandgap. Our first-principles calculations show that a minimal amount of 3 at.% Li can convert Ge from an indirect to a direct bandgap to possess a dipole transition matrix element comparable to that of typical direct bandgap semiconductors. To enhance compatibility with Si Complementary-Metal-Oxide-Semiconductors (CMOS) technology, we additionally suggest implanting noble gas atoms instead of Li atoms. We also demonstrate the tunability of the direct-bandgap emission wavelength through the manipulation of dopant concentration, enabling coverage of the mid-infrared to far-infrared spectrum. This Ge-based light-emitting approach presents exciting prospects for surpassing the physical limitations of Si technology in the field of photonics and calls for experimental proof-of-concept studies.

Synthesis, Crystal structure, electronic structure, and Raman spectra of Li4Sr2SiP4

AbstractRecently, ternary lithium phosphides have been studied intensively owing to their high lithium ion conductivities. During investigations aiming for derivatives with less lithium content the new compound Li4Sr2SiP4 was obtained. It crystallizes in the monoclinic space group P21/m (N°11) with lattice parameters of a=7.2919(8) Å, b=8.3679(6) Å, c=6.9965(8) Å, and β=90.061(9)°. The crystal structure contains isolated [SiP4]8− tetrahedra that are charge balanced by two Sr2+ and four Li+ counter ions. The structure can be derived as a superstructure of the layered CaAl2Si2 structure type comprising a hexagonal closest packing of P atoms and tetrahedral voids filled with Si and Li atoms, whereas octahedral voids are filled with Sr and Li atoms. DFT calculations confirm the structure with ordered atom positions as a global minimum and predict an indirect band gap of 2.23 eV. In addition, the experimental Raman spectrum is in good agreement with the calculated one.

Quantitative study on dynamic instantaneous dissolution of precipitated phases in 2195-T6 Al-Li alloy based on characterizations with SANS and TEM

The kinetics of the dynamic instantaneous dissolution of the precipitated phases in 2195-T6 Al-Li alloy under high strain rate loading was firstly studied quantitatively by means of the small angle neutron scattering (SANS) and transmission electron microscopy (TEM) techniques, and the thermodynamics and transformation mechanism were also illustrated in this paper. The high strain rate loadings were performed by the split Hopkinson pressure bar. The maximum flow stresses increased but the pulse durations decreased with increasing strain rates. TEM observations indicated that the size and volume fraction of the T1 phases decreased. The SANS fitting results showed that the radius and volume fraction of the T1 phase decreased after loading. The dissolution activation energy (Qd) was calculated to be 28.4 kJ/mol by combining the Johnsone-Mehl-Avrami-Kolmogorov (JMAK) equation and the Arrhenius equation, indicating that the instantaneous dissolution of T1 phase was kinetically feasible. The T1 phase generated a larger distortion energy, and the surface energy as well as the internal pressure of T1 phase increased in dissolving during dynamic loading to increase the free energy difference (driving force for dissolving) between T1 phase and matrix, making the instantaneous dissolution of the T1 phases be thermodynamically feasible. The diffusion rates of Cu and Li atoms were significantly accelerated to promote the instantaneous dissolution of T1 phase particles. The results of the Vickers hardness values showed that the hardness increased after loadings, due to the high density of dislocations and only partial dissolution of the T1 phase particles.

Li-decorated BC3 nanopores: Promising materials for hydrogen storage

In the quest of new absorbent for hydrogen storage, we investigate the capacities of slit pores formed by two BC3 sheets decorated with Li atoms. Their hydrogen storage capacities are determined using density-functional theory in conjunction with a quantum-thermodynamic model that allows to simulate real operating conditions, i.e., finite temperatures and different loading and depletion pressures applied to the adsorbent in the charge-delivery cycles. We show that the capacities of the adsorbed hydrogen phase of Li-decorated BC3 slit pores are larger than those reported recently for graphene and Li-decorated borophene slit pores. On the other hand, the usable volumetric and gravimetric capacities of Li-decorated BC3 slit pores can meet the targets stipulated by the U.S. Department of Energy (DOE) for onboard hydrogen storage at moderate temperatures and loading pressures well below those used in the tanks employed in current technology. In particular, the usable volumetric capacity for pore widths of about 10 Å meets the DOE target at a loading pressure of 6.6 MPa when depleting at ambient pressure. Our results highlight the important role played by the rotational degree of freedom of the H2 molecule in determining the confining potential within the slip pores and their hydrogen storage capacities.

Computational insight of lithium adsorption and intercalation in bilayer TiC3

Lithium-ion batteries (LIBs) have gained significant attention owing to their long lifespan. However, these batteries offer unmatched energy storage capacity and suffer from restricted lithium-ion mobility within the electrodes. Here, we employ first-principles calculation to investigate the two-dimensional TiC3 bilayer material. The results exhibit a remarkably high specific capacity of 1277 mAh/g and a low diffusion energy barrier of 0.12 eV. The TiC3 bilayer is anticipated to show high electrical conductivity, maintaining its metallicity due to strong bonding with four Li atoms. Additionally, its high thermal and dynamic stabilities are expected to significantly enhance the battery performance. Notably, the AB stacking bilayer TiC3 experiences a mere 6.01 % increase in volume, considerably smaller compared to the 28 % increase observed in the SiC bilayer. This suggests that TiC3 bilayers remain intact even at the highest concentration of lithium adsorptions. We also explored the solid-electrolyte interface (SEI) formation at the outset of battery operation using reactive force field molecular dynamics simulation. The reactive products of SEI are nicely matched with previous experimental and theoretical findings. All these intriguing properties position the TiC3 bilayer as an exceptionally promising material for use in LIBs.

External electric field driven conformation transition between lithium salts and electride-like molecules: intriguing NLO switches in Li@corannulene.

The external electric field has emerged as a powerful tool for building molecular switches with excellent properties. In this work, we investigate the impact of an external electric field on the transition between lithium salt and electride-like molecule conformations in Li@corannulene. Remarkably, the distance between the Li atom and the corannulene bottom displays a sharp increase under the influence of an external electric field strength of F-z = 110 × 10-4 a.u. As the external electric field strength increases, the Li atom brings about different directions of charge transfer (CT). The natural population analysis (NPA) charge and the molecular electrostatic potential (ESP) results show that the intermolecular CT occurs from the Li atom to the corannulene with the F-z ranging from 0 to 100 × 10-4 a.u. Interestingly, when the external electric field reaches F-z = 110 × 10-4 a.u., the CT is oriented from the corannulene to the Li atom. Moreover, electron localization function (ELF) basins are presented under an F-z of 110 × 10-4 a.u., which indicates that Li@corannulene exhibits electride-like (e-⋯[Li@corannulene]+) molecules and lithiation salt (Li+[corannulene]-) under an F-z of 0 to 100 × 10-4 a.u. Significantly, the differences in charge transfer also contribute to a significant improvement in hyperpolarizabilities (βtot) during the conformation transition from lithiation salt (Li+[corannulene]-) to electride-like (e-⋯[Li@corannulene]+) molecules. This study explores the potential of Li@corannulene as a promising second-order NLO material, and the external electric field provides an efficient strategy for designing and developing NLO switching devices.