Effect Of Lithium Intercalation Research Articles

Effects of lithium intercalation in bilayer graphene

Modulation of the Dirac cone of graphene has been highly desired to enrich the exotic properties of graphene. Intercalation of Li into multilayer graphene could lead to the gap opening of the Dirac cone of graphene. Here, using density functional theory calculations, we identify the stable intercalated structure and the corresponding evolution of band structures in the intercalation process of Li into bilayer graphene (BLG). The generalized Kekul\'e order beyond the traditional $\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$ supercell has been observed to modulate the Dirac cones of BLG by opening a gap or splitting the electron and hole pocket, contributed by the Kekul\'e-O and the Kekul\'e-Y distortion, respectively. Our work provides a further understanding of the modulation of the Dirac cone of graphene and can serve as a landmark for experiment to investigate the Li-intercalated BLG.

Anisotropic Tuning of Graphite Thermal Conductivity by Lithium Intercalation.

Understanding thermal transport in lithium intercalated layered materials is not only important for managing heat generation and dissipation in lithium ion batteries but also the understanding potentially provides a novel way to design materials with reversibly tunable thermal conductivity. In this work, the thermal conductivity of lithium-graphite intercalation compounds (LixC6) is calculated using molecular dynamics simulations as a function of the amount of lithium intercalated. We found that intercalation of lithium has an anisotropic effect on tuning the thermal conductivity: the thermal conductivity in the basal plane decreases monotonically from 1232 W/m·K of pristine graphite to 444 W/m·K of the fully lithiated LiC6, while the thermal conductivity along the c-axis decreases first from 6.5 W/m·K for graphite to 1.3 W/m·K for LiC18 and then increases to 5.0 W/m·K for LiC6 as the lithium composition increases. More importantly, we provide the very first atomic-scale insight into the effect of lithium intercalation on the spectral phonon properties of graphite. The intercalated lithium ions are found to suppress the phonon lifetime and to reduce the group velocity of phonons parallel to the basal plane but significantly to increase the phonon group velocity along the c-axis, which anisotropically tunes the thermal conductivity of lithiated graphite compounds. This work could shed some light on the search for tunable thermal conductivity materials and might have strong impacts on the thermal management of lithium ion batteries.

Effect of lithium intercalation on the structural and electronic properties of layered LiFeSO4OH and layered FeSO4OH using first-principle calculations

The effect of lithium intercalation on the structural and electronic properties of layered LiFeSO4OH and layered FeSO4OH cathode material is investigated using first-principle calculations. Results of Mulliken analysis, band gap, density of state, and charge density before and after intercalation are discussed. The importance of the strong covalent character of S–O and Fe–O bonds in high charge/discharge cycles and thermodynamic stabilities is confirmed. Analysis of the partial density of state reveals that the main contributor to the strong S–O covalent bond is the hybridization between the S 3s, S 3p electron state and the O 2p electron state. The Fe 3d orbital also plays an important role in cathode performance because it dominates the conduction and valence bands and radically changes upon the removal and insertion of lithium ion inside the cathode materials. The charge density elucidates the ionic and covalent characters of the bond inside the cathode.

Molten Carbonate Composition Effects on Carbon Electro-Oxidation at a Solid Anode Interface

The electrochemical oxidation of graphite is investigated to determine the relative influence of the composition of a molten carbonate electrolyte on a solid anode. The binary eutectics of sodium, lithium and potassium carbonates were investigated as well as ternary mixtures including the eutectic and combinations of systematically varied lithium content. It was seen that the combination of cations included in the carbonate melt can influence the electrochemical performance of graphite with binary combinations performing better than ternary in all cases. Very little change in the mechanistic behavior was observed through tafel analysis; instead it is proposed that the observed kinetic effects are a combination of the catalytic role of all metal cations present as well as the intercalation of lithium into the solid graphite electrode. The effect of lithium intercalation is suggested to lead to a change in the graphite surface polarity which affects product gas bubble formation and dislodgement at the solid anode. Increased lithium concentration, and it is assumed intercalation, encourages smaller bubbles to form which are dislodged at a faster rate than surfaces with less lithium intercalation in the ternary electrolyte. A threshold lithium concentration is reached above approximately 65 % where the electrochemical behavior is significantly changed and bubble formation behavior is no longer observed.

The effect of lithium-intercalation on the mechanical properties of carbon fibres

Carbon fibres (CFs) can be used as lightweight structural electrodes since they have high specific tensile stiffness and ultimate tensile strength (UTS), and high lithium (Li)-intercalation capability. This paper investigates the relationship between the amount of intercalated Li and the changes induced in the tensile stiffness and UTS of polyacrylonitrile-based CF tows. After a few electrochemical cycles the stiffness was not degraded and independent of the measured capacity. A drop in the UTS of lithiated CFs was only partly recovered during delithiation and clearly larger at the highest measured capacities, but remained less than 40% at full charge. The reversibility of this drop with the C-rate and measured capacity supports that the fibres are not damaged, that some Li is irreversibly trapped in the delithiated CFs and that reversible strains develop in the fibre. However, the drop in the strength does not vary linearly with the measured capacity and the drop in the ultimate tensile strain remains lower than the CF longitudinal expansion at full charge. These results suggest that the loss of strength might relate to the degree of lithiation of defectives areas which govern the tensile failure mode of the CFs.

Effect of lithium intercalation on the photovoltaic performances of photovoltachromic cells

AbstractIn the last few years, a new class of smart multifunctional photoelectrochemical devices has been attracting the interest of several academic institutions and industrial companies: photovoltachromic cells, combining the features of photoelectrochromic cells with those of dye‐sensitized solar cells. Here, we report the results of a detailed electrochemical analysis aiming at investigating the electrochemical behavior of these complex photoelectrochemical devices. In particular, we have been focused on the effect of Li+ ions displacement during the coloration of the electrochromic tungsten oxide on the performances of the photovoltaic unit. As we had previously observed striking differences between the performances of the barely photovoltaic mode (with the tungsten oxide in the bleached state) and the photovoltachromic mode (with the tungsten oxide in the colored state), we thus attempted to provide a reasonable physical interpretation to the observed phenomena. Copyright © 2013 John Wiley & Sons, Ltd.

The effect of lithium intercalation on the electronic structure of the ternary compound semiconductors ZrSe2−xSx

The electronic properties of the lithium intercalated layered transition metal dichalcogenide semiconductors ZrSxSe2−x for x = 0–2 have been calculated by density functional theory (DFT) using the WIEN2k code. The calculations have been carried out by the PBE functional and the TB-MBJ potential as proposed by Tran and Blaha. The calculations have been performed with and without spin–orbit coupling and reveal that the intercalation of lithium causes the conduction bands of LiZrSxSe2−x to shift by about 2 eV towards lower binding energy. From this, a Fermi level crossing and metallic behavior in the three intercalated compounds result. Moreover, a number of trends can be observed. Due to the contributions of the dichalcogenide p-states in the valence band the inclusion of SO coupling in the calculations lifts the degeneracy at the points Γ and A of the Brillouin zone in the same way as in the parent compounds. With regard to crystal field effects for each compound the splitting is larger at the A point than at the Γ point and the absolute value of the splitting increases with the atomic number of the chalcogenide. In particular, the simple Fermi surface consisting solely of barrels centered along the LML line makes LiZrSxSe2−x a promising Fermi liquid reference compound.

Effect of Al-doping on lithium nickel oxides

The electronic structures of LiNiO2, LiAlO2 and LiNi0.5Al0.5O2 are investigated using density-functional theory (DFT) in the local-density approximation (LDA). The effect of lithium intercalation and the influence of aluminium doping on the structure and electrochemical properties of LiNiO2 are discussed. An increase in the open circuit voltage is observed with Al doping in LiNi0.5Al0.5O2 compound.

Transport-Limited Recombination of Photocarriers in Dye-Sensitized Nanocrystalline TiO2 Solar Cells

The effect of lithium intercalation on the transport dynamics and recombination kinetics in dye-sensitized nanoparticle TiO2 solar cells at lithium levels below 5 atom % was investigated by photocurrent and photovoltage transient and spectroelectrochemical techniques. Titanium dioxide films were doped electrochemically in the dark and under illumination. It was discovered that when Li+ is present in the electrolyte, lithium intercalates irreversibly into dye-sensitized TiO2 films at open circuit (ca. −0.7 V) under normal solar light intensities. Photocurrent transients of doped nonsensitized TiO2 films indicate that lithium doping decreases the diffusion coefficient of electrons through the nanoparticle network. Photocurrent and photovoltage transients of sensitized TiO2 films provide the first evidence that electron transport limits recombination with the redox electrolyte in working cells. As the Li density in the films increases, the diffusion and recombination times of photoelectrons increase proporti...

Electrochemical lithium intercalation into the Bi-2212 phase

Effects of lithium intercalation into the Bi-2212 phase on its structural and superconducting properties were studied using monophasic samples of Bi 2Sr 1.5Ca 1.5Cu 2O z lithiated through an electrochemical method at a constant applied voltage at room temperature. The amount of doped lithium was found by 1CP analysis to be in the range of 0 ≤ y ≤ 0.37 for Li y Bi 2Sr 1.5Ca 1.5Cu 2O z depending upon experimental conditions. However, the oxygen content determined by coulometric titration remained almost unchanged after the lithiation. The electrochemical lithium intercalation led to a very interesting change in T c though the original tetragonal structure and oxygen content remained essentially the same: T c first increased rapidly as y increased, reached a maximum of 94 K, and then decreased to zero. The drastic T c change is ascribed to a decrease in the hole concentration. Thus, the electrochemical lithium-doping provides us with a great advantage of easily controlling T c at room temperature by changing electrochemical conditions while keeping the original crystal symmetry.

The Effect of Lithium Intercalation on the Crystal Structure and Magnetic Property of Layered FeWO4Cl

LiFeWO4Cl has been prepared by reductive intercalation of lithium into FeWO4Cl. FeWO4Cl crystallizes into a tetragonal system (space group P4/nmm) with cell dimensions of a=6.677(5) Å and c=5.270(5) Å, while lithium intercalation gives rise to the formation of a monoclinic phase ( P21/m) with cell dimensions of a=7.050(0) Å, b=6.926(2) Å, c=5.043(0) Å and β=92.54(2)°. Infrared (IR) spectroscopic analyses of FeWO4Cl and LiFeWO4Cl show that the symmetry of the tetrahedral WO42- group in FeWO4Cl becomes reduced as the lithium intercalate into its two-dimensional lattice, indicating an alternately ordered lithium occupancy of half of the octahedral interlayer sites. The effective magnetic moments of FeWO4Cl and LiFeWO4Cl were estimated to be 5.95 and 5.10 B.M., respectively, which can be attributed to the selective reduction of a high-spin ferric ion to a high-spin ferrous one upon lithium intercalation. It was also found that the two-dimensional magnetic property of FeWO4Cl was changed to a three-dimensional one in LiFeWO4Cl owing to the c-axis contraction.

Effect of Lithium Intercalation on Lattice Dynamics of Molybdenum Disulfide

AbstractIn order to explain new peaks in the Raman spectra of MoS2 after intercalation with Li, the lattice dynamics in LixMoS2 is calculated by applying the central force model. It is found that they can be attributed to new vibrational modes in which the intercalant atoms strongly vibrate against the host lattice. The force constants between Li and S atoms are much smaller than the intralayer force constants and have almost the same order value as the interlayer ones.

Lithium insertion into indium sesquiselenide

The effects of lithium intercalation in In 2Se 3 have been studied using different methods. Electrochemical properties of the non-stoichiometric Li xIn 2Se 3 phase are given in the range 0 ⩽ × ⩽ 1 for either quenched or annealed compounds. Electronic conductivity has been measured during the insertion process in n-butyl lithium and suggests weak charge transfer. The relation between the morphology of samples and insertion mechanism have been discussed.

Effect of lithium intercalation on the electrical properties of inse single crystals

Effect of lithium intercalation on the electrical properties of inse single crystals