Lithium Atoms Research Articles

(Best Poster Award - 1st Place) Characterisation of the Li Metal|Electrolyte Interface of PEO-Based SPEs with Borate Salts, Using in Situ Li Deposition PES Measurements Aided by AIMD Simulations

Lithium metal and anode-free batteries has the potential to increase the energy density and specific energy of the batteries drastically. However, when regular electrolyte materials are tried for these concepts they are plagued with problems due to degradation of the electrolyte at the interface and processes like dendrite formation which leads to poor capacity retention.[1] A strategy to mitigate these problems is to use Solid Polymer Electrolytes (SPEs), as these have better stability towards lithium metal. In order to find appropriate chemistries to use in SPE-based cells it is important to investigate and understand their anode interface, as this is where the Solid Electrolyte Interphase (SEI) is created from the degradation products during cycling.This work investigates three polyethylene oxide (PEO)-based SPEs, using lithium tetrafluoroborate (LiBF4), lithium bis(oxalate)borate (LiBOB), and lithium difluoro(oxalate)borate (LiDFOB) as the lithium conducting salts. The interfaces of these SPEs (PEO:LiBF4, PEO:LiBOB, and PEO:LiDFOB) was studied using Photo-Electron Spectroscopy (PES) with in situ lithium deposition, where lithium atoms are evaporated on top of the SPE film. The analysis of the core-level spectra before and after lithium deposition is compared to Ab Initio Molecular Dynamics (AIMD) simulations of the interface, where lithium atoms are gradually added during the simulation. These experimental and theoretical methods are meant to mimic the electrochemical plating of lithium at the lithium|SPE interface during charging of a lithium metal or anode-less cell.The interfaces of PEO:LiBOB and PEO:LiBF4 show, among other compounds, polyethylene as a breakdown product at the interface. PEO:LiDFOB shows a much lesser degree of degradation compared to the other two systems. The degradation layer is however still effective at protecting the SPE from further breakdown, as PEO:LiDFOB has a relatively high capacity retention compared to PEO:LiBF4 and PEO:LiBOB. Suggested is that the LiF provides a better electrochemical stability, while the boron and oxalate breakdown products provides a higher mechanical stability at the interface.[1] Huang WZ, Zhao CZ, Wu P, Yuan H, Feng WE, Liu ZY, Lu Y, Sun S, Fu ZH, Hu JK, Yang SJ. Anode‐Free Solid‐State Lithium Batteries: A Review. Advanced Energy Materials. 2022 Jul;12(26):2201044. Figure 1

Intercalation Pathway in Graphite Particles Analyzed with a Multi-Layer Phase Field Model

Graphite is today the most common negative electrode material in commercial cells, alone or blended with silicon, thanks to its relatively high specific capacity of 372 mAh·g−1, its excellent cycling stability, its low thermodynamic potential, and relatively low cost compared to alternative materials. The increase in the energy densities, power capabilities, and durability of lithium-ion batteries using this conventional cost-effective active material is possible through an optimization of the electrode and material designs. Such optimization requires, however, knowledge of the fundamental mechanisms that govern both the lithium transport inside graphite particles and the electrochemical transfer at the electrolyte / active material interface.Graphite has an ideal lamellar structure made of graphene sheets. During intercalation, the lithium atoms insert between the graphene planes, with almost no lithium transport across the graphene sheets. The interactions between lithium atoms in adjacent galleries leads to the formation of structures with filled layers separated by a number of empty layers, known as stages. Given this phenomenon, graphite active material undergoes phase separation between successions of several stable phases during lithium intercalation. This staging phenomenon influences the critical properties of graphite like its equilibrium potential, lithium diffusion or lithium insertion kinetics.In the present work, we use a Cahn-Hilliard type model, adapted to multi-layered materials1 and study the influence of the parameters in the underlying free-energy models. We focus first on the intra-layer and inter-layer lithium interaction contributions. Free-energy models with increasing complexity of inter-layer interactions are introduced and discussed based on their corresponding phase diagrams. In particular, we show that occurrence of fractional 3/2 stage, observed for potassium or rubidium intercalation in graphite at high pressure, requires an interlayer interaction effective at second neighbor, while a continuous screening effect of the intercalant is necessary to predict the occurrence of stages greater than 2 without the occurrence of the fractional 3/2 stage, as observed for lithium2.The kinetics of stage formation and evolution is also greatly affected by the interaction parameters of the free-energy model. A linear stability analysis (LSA) is performed to investigate the impact of the free energy model parameters on the stage formation dynamics and growth rates. In particular, the LSA shows that stage 2 grows the fastest, even for low lithium filling fraction. In accordance with this result, simulations of spinodal decomposition from moderate homogeneous lithium filling fraction (c=0.3) shows the formation of stage 2 at early times before an evolution towards stage 3 (See figure 1). This higher growth rate of stage 2 seems to have an impact on lithium intercalation pathway. Indeed, during simulations of lithium intercalation in a graphite particle at different C-rates, stage 2 tends to form very early at the electrolyte/particle interface, even when stage 3 and dilute stage 1 dominates inside the particle. The simulation of lithium intercalation also provides access to the effective exchange current density as function of the averaged surface concentration. The presence of the stages at the surface of the particles directly affects this averaged exchange current density. It results in non-symmetric exchange current density profiles, in coherence with operando X-ray micro-diffraction measurement in thick graphite electrodes3.Figure 1: Snapshots of a spinodal decomposition at different times. The initial average filling fraction is c=0.3 and the system has six layers. For each subfigure, top: lithium content in each layer, bottom: coefficients of the Fourier transform used to track the stages Smith, R. B. et al. Intercalation Kinetics in Multiphase-Layered Materials. J. Phys. Chem. C 121, 12505–12523 (2017).Chandesris, M., et al. Thermodynamics and Related Kinetics of Staging in Intercalation Compounds. J. Phys. Chem. C 123, 23711–23720 (2019)Tardif, S. et al. Combining operando X-ray experiments and modelling to understand the heterogeneous lithiation of graphite electrodes. J. Mater. A 9, 4281–4290 (2021) Figure 1

Novel Operando Nuclear Magnetic Resonance Approach for Tracking the Electrode State of Charge in Li/Na-Ion Batteries

Lithium and sodium-ion batteries have become the focal point of interest for the energy transition due to their promising applications for electric cars and energy grid storage. Operando characterization of batteries is critical to understand the degradation processes and increasing their electrochemical performance, especially in abusive conditions like during fast charges. Knowledge of the redox state of each electrode is essential to identify the origins of capacity loss in full batteries. Among the methods used for these investigations, operando Nuclear Magnetic Resonance (NMR) methods are promising since, without destroying the battery, they enable monitoring in real-time the electrochemical processes and the formation of short-lived metastable or reactive phases [1,2].Up to now, most operando NMR studies have focused on 7Li NMR spectroscopy to follow the lithiation and degradation processes in the solid electrodes of lithium-ion batteries. However, the large shifts and broadenings of the NMR spectra, which result from the redox-active paramagnetic ions (Ni2/3+, Co4+, Mn3/4+) or from the metallicity of the electrodes [3], complicate operando NMR spectra acquisition and interpretation for full batteries.Herein, we demonstrate that the 1H operando NMR signal of the liquid electrolyte solvent can be used to spy on the positive electrode evolution while benefitting from the high sensitivity of 1H liquid-state NMR compared to 7Li NMR. So far, operando NMR using the liquid electrolyte signal was mainly exploited to follow electrolyte decomposition [4] or to image indirectly dendrite formation [5]. Contrary to the lithium or sodium atoms composing the electrodes, hydrogen atoms in the electrolyte solvent are not a direct probe of the state of charge of the electrode. We demonstrate that the 1H NMR signal of the electrolyte molecules in the battery is, however, highly sensitive to the magnetic susceptibility (and therefore the redox state) of the neighboring particles of positive electrode active material.The state-of-charge (SOC) of the positive electrodes in the charging battery can be tracked indirectly through distortion in the spectrum of the dimethyl carbonate (DMC) solvent near the positive electrode. The effect of the other battery components such as current collectors, separators, or even negative electrodes is shown to be negligible compared to the perturbations induced by the positive electrode. We define specific descriptors to track the changes in the distorted 1H NMR spectrum of the battery and we correlate these changes with the state-of-charge of the positive electrode inside the battery as it is charged and discharged. This approach will enable measuring, operando, the redox state of positive electrodes in batteries, even when their 7Li signals cannot be detected by NMR. Exact knowledge of the redox state will contribute to a better exploitation of the electrochemical curves in full batteries.[1] Bagheri, K.; Deschamps, M.; Salager, E. Nuclear Magnetic Resonance for Interfaces in Rechargeable Batteries. Current Opinion in Colloid & Interface Science 2023, 64, 101675. https://doi.org/10.1016/j.cocis.2022.101675.[2] Liu, X.; Liang, Z.; Xiang, Y.; Lin, M.; Li, Q.; Liu, Z.; Zhong, G.; Fu, R.; Yang, Y. Solid‐State NMR and MRI Spectroscopy for Li/Na Batteries: Materials, Interface, and in Situ Characterization. Advanced Materials 2021, 33 (50), 2005878. https://doi.org/10.1002/adma.202005878.[3] Grey, C. P.; Dupré, N. NMR Studies of Cathode Materials for Lithium-Ion Rechargeable Batteries. Chemical Reviews 2004, 104 (10), 4493–4512. https://doi.org/10.1021/cr020734p.[4] Wiemers-Meyer, S.; Winter, M.; Nowak, S. NMR as a Powerful Tool to Study Lithium Ion Battery Electrolytes. Annual Reports on NMR Spectroscopy 2019, 121–162. https://doi.org/10.1016/bs.arnmr.2018.12.003.[5] Ilott, A. J.; Mohammadi, M.; Chang, H. J.; Grey, C. P.; Jerschow, A. Real-Time 3D Imaging of Microstructure Growth in Battery Cells Using Indirect MRI. Proceedings of the National Academy of Sciences 2016, 113 (39), 10779–10784. https://doi.org/10.1073/pnas.1607903113.

Computationally Predicted New Solid-State Electrolyte (Li5+x PS4+x Cl2-x : 0 ≤ x ≤ 2) and Poly Sulfide Cathodes (Li3+y PS9 or Li5+y PS9Cl2: 0 ≤ y ≤ 9) for High Performance Li Metal Anode Batteries

We used Molecular Dynamics (MD) simulations to study the structures and conductivity of sulfide-based ceramics from the superionic conductor argyrodite family for applications as solid-state electrolyte and cathode materials. These studies combined quantum mechanics (QM) and ReaxFF reactive force field based MD, where the ReaxFF parameters were developed from QM MD.[1]Currently Li10GeP2S12 (LGPS) demonstrates one of the highest Li-ion conductivity for solid state electrolyte, 12 mS/cm at 300K, but it is highly reactive with the Li-metal anode, and it is expensive due to the presence of Ge. We studied the Li ion diffusion mechanism and ionic conductivity of the promising Li6(PS4)SCl solid state electrolyte, predicted to have a conductivity of s = 6 mS/cm, close to experiment (4 mS/cm). We find that Li migration in this electrolyte occurs via conjugated substitutional type diffusion involving rearrangements of three (or more) Li-ions and ~ 3 vacant sites in a 3D matrix of anions that are essentially stationary at 298K (over 20 ns of simulation). We carried out 10 ns of MD simulation to predict a Li-ion conductivity for a single phase Li6(PS4)SCl of 5.9 mS/cm in agreement with solid state NMR measurements of 3.9 mS/cm. Our calculated activation energy of 0.24 eV is within experimentally reported range.[2]We report here the computationally predicted structure of Li5PS4Cl2, a new sulfide Li-superionic conductor with the highest Li-ion conductivity at solid state, which we predict to have Li-ion conductivity of 20 mS/cm at 298 K. We also predicted the directional ionic conductivity and Li-migration barrier in it. This Li5PS4Cl2 has not yet been synthesized and studied experimentally.We also report our results on QM and ReaxFF MD for new polysulfide cathodes, Li3+y PS4+n and Li5+y PS4+nCl2 , both based on Li3PS4. Here, n is the number of excess sulfur atoms in the fully charged polysulfide cathode per formula unit with y=0 and y is the excess Li added to the cathode during discharge processes. We evaluated the performance of these cathode electrolyte systems in terms of interfacial stability and discharge voltages.Li3PS4+5 is a potential cathode for lithium-sulfur batteries. We predicted the structures of Li3PS4+5 finding extra S3 and S7 chains attached to one S atom of each PS4 group. This leads to a density of 2.2 g/cm3. As the cathode is discharged, the lithium atoms fill up all the gaps between S atoms, leading to Li3+9 PS4+5, with 1.7 g/cm3. We studied the dynamics of the discharge as lithium ions from the metal move into the material and react with the S-S bonds to make Li2S. Our predicted discharge curve agrees well with the experimental data (Figure 1).[3]We extended these studies to design a new polysulfide cathode Li5PS4+5Cl2 to be used with our newly predicted Li-superionic conductor electrolytes. The interfacial stability of the Solid electrolyte with S-based cathode and with Li-anode were studied (Figure 2).Our work presents a new strategy for designing materials and processes for solid-state batteries using computational screening and chemical substitution. This demonstrates the potential of using lithium PS4 based superionic conductors with PS4 based cathodes for applications in solid-state batteries. We also addresses some of the key challenges in accelerating solid-state battery development, such as phase stability, transport properties, electrode compatibility etc. This work demonstrates how computational studies can guide new avenues for experimental developments to advance of solid-state battery technology for applications ranging from grid storage to electric vehicles.Acknowledgements:We acknowledge the support from Hong Kong Quantum AI Lab, AIR@InnoHK of Hong Kong Government.

First-principles study on the electronic structure and lithium intercalation performance of MnV2O6

The electronic structure and lithium intercalation capability of MnV2O6 were studied using the first principles of density functional theory (DFT), through binding energy, volume change rate, band structure, and density of states after lithium is embedded. The experimental results show that lithium atoms in MnV2O6 unit cells without causing noticeable structural changes. The band gap of MnV2O6 is 1.559 eV; The intercalation of lithium atoms reduce the band gap, rendering it conducive for electron excitation from the valence band to the conduction band.

Molecular Dynamics Study of the Structural and Diffusion Properties of Dehydrated Layered Double Aluminum and Lithium Hydroxide

An atomistic model of dehydrated Cl-doped double layer aluminum–lithium hydroxideLi⋅Al2(OH)6Cl(DALH-Cl), which is a promising material for the sorption of lithium from weak brines, has been developed. The effective charges of the atoms of the system have been determined using the density derived electrostatic and chemical (DDEC6) methods. A molecular dynamics analysis of DALH-Cl has been performed within the developed model. The structural characteristics of three atomic pairs in metallic layers of DALH-Cl and the probability density distribution of atoms in the direction perpendicular to these layers have been calculated. The temperature dependence of the diffusion coefficient of lithium atoms in the space between metallic layers in the temperature range of 325–450 K has been evaluated.

Pressure-Assisted Synthesis of Highly Crystalline 1T''-Lix MoS2.

Lix MoS2 is not only a lithium battery material, but is also an important precursor for the synthesis of MoS2 nanomaterials. Current syntheses of MoS2 , such as in n-butyllithium/LiBH4 or electrochemically, are not satisfying in terms of defined stoichiometry and crystallinity, so an accurate experimental crystal structure determination of this important and widely used material has been long awaited. A high-pressure/high-temperature synthesis yielded highly crystalline 1T''-Lix MoS2 (x=1, 1.333). 1T''-LiMoS2 crystallizes in the space group P with a=6.2482(3) Å, b=6.6336(3) Å, c=6.7480(3) Å, α=119.321(2)°, β=90.010(2)° and γ=90.077(2)°. The arrangement of Mo atoms within the b-c-plane confirmed a predicted Peierls distortion. A similar atom distribution pattern to that of Mo is also observed for the lithium atoms. Calculation of bond valence site energies gave an activation barrier of 1.244 eV for 2D lithium-ion migration. For x=1.333, a phase-pure synthesis was achieved.

Intercalation of Lithium Atom/Ion in carbon, Silicon and Germanium Nanotubes

In this paper, we have studied the impact of Li atom/ion intercalation in C, Si and Ge nanotubes. The bond lengths for the optimized structures of the Li atoms/ions intercalation are similar and consistent with the bond lengths of pristine nanotubes. Based on Mulliken population and charge density analysis,there is a net transfer of charge from Lithium atoms to nanotube atoms. However, it is opposite in case of ion intercalation. The intercalation of Li atom/ion alters the electronic structure of the SWNTs, resulting in a shift from semiconducting to metallic. Our study also reveals that the conductance is 5G 0 for GeNT on Li atom/ion intercalation, which is 2G 0 for pristine GeNT. Due to their enhanced conductance as compared to pristine nanotubes, Li atom/ion intercalated systems can also be expected as materials for nano scale electronic devices, perfect for ballistic transport.

First-Principles Study of Titanium and Lithium Adsorption on Perfect and Defective Hexagonal Boron Nitride Monolayer Under Effects of Charging

Single Titanium (Ti) and Lithium (Li) atoms adsorption on Pristine and defective hexagonal boron nitride (P-h-BN and BV-h-BN) monolayer were employed using Density Functional Theory (DFT) under effect of charging. Obtained data reveal that Li adsorption on P-h-BN is weak, while Ti adsorption on P-h-BN is strong. When Ti and Li atoms interact with P-h-BN surface, Ti and Li generate 4 µB/cell and 1 µB/cell magnetic moments, respectively. The extraction of an electron from the systems leads to a considerable rise in the adsorption energy, notably in the case of Li-P-h-BN. There is a notable decrease in the band gap of Ti-P-h-BN in both the charged states, especially in the electron-added state. Removing an electron from the Li-P-h-BN system results in a non-magnetic state and a significant increase of the band gap to 4.07 eV. Ti-BV-h-BN system shows significantly stronger adsorption energy due to the d-orbitals of the Ti atom. When an electron is added to the systems, the interaction energy between Ti and BV-h-BN decreases, while the interaction energy between Li and BV-h-BN increases. Moreover, removing an electron from Ti-BN-h-BN increases the band gap to 2.29 eV and the disappearance of the magnetic moment.

Energy Landscapes for Lithium Incorporation and Diffusion in Multidomain Silicon Suboxide Anode Materials.

In-depth understanding of the lithium interaction characteristics within multidomain silicon suboxide is indispensable for optimizing the electrochemical performance of silicon suboxide anode materials for lithium-ion batteries. In this study, we investigate the domain-dependent thermodynamic and kinetic properties of lithium atoms within systematically designed multidomain silicon suboxide models composed of Si, SiO2, and Si/SiO2 interface by performing a series of computational simulations combined with a unique tomography-like sampling scheme. We find that the Si/SiO2 interfacial region exhibits preferential thermodynamics and kinetics for lithiation and can serve as a critical lithium transport channel during charge-discharge cycles, while the SiO2 domain is likely to be excluded from lithiation due to its high resistance to lithium diffusion. Consequently, a significant fraction of lithium is expected to be trapped at the Si/SiO2 interface during the discharge process, which ultimately contributes to a low initial Coulombic efficiency. This theoretical understanding suggests that the formation of continuously connected lithium-transportable Si/SiO2 interfacial channels surrounding the Si domains, along with a well-structured shallow SiO2 framework through the use of appropriate synthesis methods, is essential for maximizing the electrochemical performance of silicon suboxide anode materials.

Effect of Dopants on Σ3 (111) Grain Boundary in Diamond

Extensive research has been conducted on electronic properties of metal‐doped diamond for electrochemical applications. The codoped diamond has emerged as an important strategy to enhance their performance and impart novel characteristics. In the present investigation, density functional theory calculations are used to envisage the structural, electronic, and elastic properties of nitrogen‐vacancy (N‐V) and silicon‐vacancy (Si‐V) defects at the Σ3 (111) grain boundary (GB) in diamond. Further, the Li and Na atoms are introduced as a dopant into these defective structures, referred as Σ3Li(N‐V), Σ3Na(N‐V), Σ3Li(Si‐V), and Σ3Na(Si‐V). The results reveal that the doped structures considered in the investigation are energetically and dynamically stable. The presence of defects (i.e., dangling bonds due to the presence of vacancies and dopants) at the Σ3 (111) GB significantly alters the overall electronic property of the diamond. The adsorption energies calculated for the doped systems range from −1.2 and 8.38 eV. The Σ3Li(N‐V) shows negative adsorption energy, indicating the tendency of lithium atom to adsorb exothermic onto the GB of Σ3N‐V, whereas, other adsorptions are endothermic in nature. The choice of dopant plays a substantial role in altering the properties of diamond, while the mechanical properties of the investigated Σ3 (111) diamond structures vary marginally.

Synthetic pathway of shallow n-type donor: Theoretical study of Li and B co-doped diamonds

To find potential n-type diamonds with shallow donor energy levels and low formation energies, the thermodynamic and electronic properties of Lithium-Boron (LiB) co-doped diamonds have been investigated using density functional theory (DFT) and hybrid density functional theory (HSE06). The structure, formation energy, electronic property and the potential synthesis pathway are analyzed. The results of the single Li defect is not a suitable candidate for a shallow n-type donor, as it distorts the diamond lattice and forms clusters, in agreement with previous work. The calculated ionization energy of Lii2-B defect (0.29 eV) and the impurities formation energy (0.196 eV) is much lower than that of Lii defect. It suggests that the introduction of B helps improve the solubility of Li in diamond. Further structural analysis has shown that the incorporation of B atoms inhibits the diffusion of Li atoms and simultaneously reduces the internal strain in the diamond, resulting in a significant reduction in the distance between the two lithium atoms from 2.061 Å to 1.629 Å. At last, a non-molecular synthesis pathway of Lii2-B co-doped diamond is proposed via prior generation of B-doped diamond at which Li atom is mobile which indicates there is a potential window-of-opportunity to prepare Lii2-B co-doped diamond to achieve n-type diamond.

Diffusion and Creep in Lithium Metal Anodes Induced by Plating and Stripping Reactions

Electrodeposition of lithium on lithium metal negative electrodes (anodes) of liquid cells produces filamentary deposits, resulting in poor cycling efficiency. Experiments suggest that filaments grow by extrusion of metal from the substrate, due to compressive stress introduced during deposition. A model is presented that explores the origin of stress generated in the anode during plating-stripping cycles. According to the model, plating or stripping reactions insert or remove lithium atoms at the interface between the metal and the solid electrolyte interphase (SEI) layer. Stress is induced by the resulting diffusion processes, with diffusion-induced strain accommodated by inelastic creep. Stress distributions during cycling are calculated, and are used in turn to predict curvature transients that would be measured in beam-deflection experiments. The calculations account for the three-dimensional surface morphology, since surface features that protrude above the surface plane do not contribute to curvature changes. Comparisons with recent curvature measurements demonstrate detailed agreement, with diffusion and creep parameters close to literature values. The results support the hypothesis that electrochemical reactions intrinsically generate stress. The model can serve as a framework for analysis of morphogical instability of the lithium anode interface in both liquid and solid-state cells.

Prospective utilization of boron nitride and beryllium oxide nanotubes for Na, Li, and K-ion batteries: a DFT-based analysis.

In the present work, we investigated the adsorption mechanism of natural sodium (Na), potassium (K), and lithium (Li) atoms and their respective ion on two nanostructures: boron-nitride nanotubes (BNNTs) and beryllium-oxide nanotubes (BeONTs). The main goal of this research is to calculate the gain voltage for Na, K, and Li ionic batteries. Density function theory (DFT) calculations indicated that the adsorption energy between Na + is higher than that of the other cations, and this is particularly clear in the BeONT. Furthermore, gain voltage calculations showed that BNNTs generate a higher potential than BeONTs, with the most significant difference observed in BNNT/Na + . This research provides theoretical insights into the potential uses of these nanostructures as anodes in Na, K, and Li-ion batteries. Density function theory used to compute the ground state properties for BeONT and BNNT with and without selected atoms and their ions (Li, K, and Na). B3LYP used for exchange correlation between electrons and ions, and 6-31G* basis set used for all atoms and ions. Gauss Sum 2.2 software used for estimate the density of state (DOS) for all structure under investigation.

Uncovering the lithium-embedded behavior and catalytic mechanism of g-C3N4 as a sulfur host of lithium‑sulfur batteries in the initial discharge reaction

Due to its excellent anchoring properties to lithium polysulfide (LiPSs), g-C3N4 has been widely studied as anode material for lithium‑sulfur batteries (LSBs). g-C3N4 as the electrode material has an obvious irreversible capacity during the initial discharge progress. The mechanism of this irreversible reaction and its effect on the adsorption of LiPSs and cycling performance of g-C3N4 are not clear. Using first-principle calculations, founding that during the initial discharge progress, the binding energy of lithium to the heptazine ring is larger than the binding energy of lithium to sulfur resulting in this part of lithium entering the center of the heptazine ring and being unable to desorption form Li@g-C3N4, which is the main reason for the irreversible capacity. However, compared with g-C3N4, the conductivity of Li@g-C3N4 is enhanced and the diffusion of lithium atoms is facilitated not only by avoiding the strong interaction of other Li atoms with g-C3N4 because the vacancies have been filled. And the adsorption of LiPSs is also appropriately weakened, which can better maintain the structure integrity of the Li2S6 and Li2S8 molecules and lead to a lower reaction free energy during the discharge process.

Compressed lithium atom under Debye screening

AbstractIn the present paper, we introduced two approximation methods to investigate the spherically compressed lithium atom under the influence of Debye plasma. Specifically, the diffusion and the variational Monte Carlo methods are used for the first time to study this case. We incorporated an exponential screening into the nuclear Coulomb potential to account for the plasma influence. We focused our investigation on analyzing the combined effect of compression and plasma environment on the behavior of the lithium atom in its ground state. The resulting outcomes exhibited consistent pattern across various confinement radii and Debye plasma lengths . Many of the results are novel contributions, as they have yet to be explored. Moreover, the findings from this study demonstrated reasonable agreement with the limited existing theoretical results.

Thermal conductivities of ultra-lightweight -based type-VII clathrates: an ab initio and comparative study

Caged carbon clathrates may have profound applications in thermoelectrics due to their inherent host–guest relations. Using ab initio techniques, we investigate the electronic and phononic properties of type-VII clathrate, which is a prototype of the widely studied ternary X–B–C clathrate, and tune its properties using lithium atom filling and boron atom substitution. Upon the introduction of pairwise B substition and a Li filler, the half-filled and fully filled structures retain their semiconducting characteristics due to balanced electron counts; however, their indirect band gaps are reduced. By comparing the phonon and thermal properties of filled and empty structures, we show that B substitution and Li fillers lift the phonon degeneracies, increase the three-phonon scattering phase spaces and eventually cause tenfold reductions in the relaxation time of phonons. The Li filler-induced rattling of phonon modes and resonant scattering channels, which are validated by the peak features of phonon density of states and scattering rates, efficiently reduce the room temperature thermal conductivity for fully filled structures. Our findings indicate the efficiency of heteroatomic substitution and fillers to engineer the phonon and thermal properties of carbon-based clathrates.

Lithium doping effect on structural, electronic and optical properties of KCaF3 fluoroperovskite: DFT insights using GGA-PBE

In order to evaluate the effects of Lithium (Li) doping on the various properties of KCaF3, we present first-principles calculations built on density functional theory (DFT) and employing approximation GGA-PBE. The compound possesses a 2 × 2 × 1 supercell and cubic geometry with space group pm3m. By putting the TDOS and PDOS concepts into practice, the effects of Li-doping on electronic structure and, consequently, optical characteristics have been investigated and evaluated in detail. With the formation of new states in band structure, the substitution of the Lithium (Li) atom for the Calcium (Ca) atom drastically adjusts the electronic band structure. The indirect bandgap of pure KCaF3 was measured to be 5.37 eV. The band gap was slightly shrunk as a result of changes in Li concentration. This causes the indirect band gap of KCaF3 to change to the direct band gap for Li-doped KCaF3. A strong interaction between the Li atom and the atoms around it is seen and the density of states for Li-doped KCaF3 relocates at slightly lower energies. Additionally, there is a noticeable change in the partial density of states of KCaF3 near the conduction band bottom, leading us to believe that Li-doping has an impact on the electronic band structure. Investigations into the optical characteristics of doped and undoped KCaF3 and correlations with its electrical structure are made. The massive difference in optical characteristics and band gap (i.e., indirect to direct) caused by Li-doping makes this substance a desirable candidate for optoelectronic materials.

High-temperature test of tin-lithium CPS under deuterium plasma irradiation conditions

This paper is devoted to experiments on testing of the Sn-Li capillary porous system (CPS) under conditions of deuterium plasma irradiation, carried out at a plasma-beam installation (PBI). As a metal CPS matrix, molybdenum mesh was used. The paper presents a detailed description of the development of technology and procedure for the fabrication of the investigated sample, intended for plasma testing, as well as experiments on irradiation of Sn-Li CPS with deuterium plasma. As a result of the experiments performed, the dependences of the temperature of the investigated sample on the energy of the plasma contacting with the CPS, time dependence of the gas phase composition in the PBI chamber during irradiation of Sn-Li CPS with deuterium plasma, optical spectra depending on the temperature were obtained. Post-experimental material science studies with a sample of Sn-Li CPS were also performed and the results of microstructure, thermal and X-ray phase analysis were obtained. Analysis of the experimental data obtained showed that the energy of deuterium plasma precipitated on the Sn-Li alloy is re-emitted into the energy of optical radiation on the evaporating neutral atoms of lithium and tin. A complete evaporation of the alloy from CPS, during interacting with deuterium plasma, leads to partial destruction of the metal matrix of molybdenum.

Dendrite-free lithium anode enabled by lithium atom preferred orientation on Al[sbnd]Li alloy

Li-rich composite alloys have received increasing attention as a method of inhibiting lithium dendrites. The Al-Li alloy has earned favor as a viable option to stabilize Li metal anodes due to its low cost, low flammability, natural abundance, and ease of operation. However, the mechanism responsible for the inhibition of lithium dendrites in the Al-Li alloy has yet to be thoroughly researched. Through Density Functional Theory (DFT) calculations, we analyzed the adsorption energies of Li atoms on various lattice planes of bare Li metal and Al-Li alloy. We discovered that Al-Li alloy provides higher absorption energies of Li atoms, ultimately leading to the preferred orientation of lithium atoms on Al-Li alloy. Experimental data confirmed our hypothesis, the symmetric cells with an Al-Li alloy demonstrated superior cycling properties over 140 hours, particularly at a current density of 5 mA cm−2, compared to the bare Li anode. Furthermore, full cells with an LiFePO4 (LFP) cathode exhibited better cycle and rate performance. This work provides a reasonable explanation for the inhibition of lithium dendrites on Al-Li alloy.