The determination of Li+ mobility in solid electrolyte Li1.3Al0.1Zn0.1Ti1.8P3O12 in view of ionic diffusivity and conductivity

Nasicon-type solid electrolyte Li_1.3Al_0.1Zn_0.1Ti_1.8P₃O₁₂ was prepared by citric acid-assisted acrylamide polymerisation gel method. X-ray diffraction pattern showed that the introduction of Zn²⁺ in the parent matrix Li_1+x Al _x Ti_2?x P₃O₁₂ made it easier to get high-purity rhombohedral structure (space group $ R\overline 3 C $ ) Li_1.3Al_0.1Zn_0.1Ti_1.8P₃O₁₂ without the evidence of impurity secondary phase. The Li⁺ kinetics were investigated by complex impedance in bulk pellet and ionic conductivity in battery-type composite cathode, respectively. Grain-interior resistance measured by galvanostatic intermittent titration technique, potential step chronoamperometry, and AC impedance spectroscopy at 20 °C varies in the range 1.2–1.95?×?10^?4?S?cm^?1, which is in good agreement with that obtained by complex impedance method 1.5?×?10^?4?S?cm^?1.     

7Li NMR study on Li+ ionic diffusion and phase transition in LixCoO2

The temperature dependence of the spin-lattice relaxation time, T₁ and the line width of the ⁷Li nucleus were measured in delithiated Li_xCoO₂ (x = 0.6, 0.8, 1.0). Two different relaxation behaviors were observed in the temperature dependence of T₁^− 1 in a x = 0.8 sample. These would have arisen from inequivalent Li sites in two coexisting phases; an original hexagonal (HEX-I) and a modified hexagonal (HEX-II) phase in the x = 0.8 sample. We analyzed using a phenomenological non Debye-type relaxation model. Motional narrowing in the line width was observed in each sample, the result revealing that Li⁺ ions begin to move at low temperature in samples with less Li content. It was found that the activation energy associating with Li⁺ ion hopping in the HEX-II phase is smaller than that in the HEX-I phase. These results show that the HEX-II phase produced in the Li deintercalation process would be suitable for Li⁺ ionic diffusion in multi-phase Li_xCoO₂, and it is expected that this would enable fast ionic diffusion. Li⁺ ionic diffusion related to phase transition is discussed from ⁷Li NMR results.     

Exploring low temperature Li+ ion conducting plastic battery electrolyte

We report blend-based plastic polymer electrolyte (i.e., polyethylene oxide (PEO)–polydimethyl siloxane (PDMS)–lithium hexafluorophosphate (LiPF₆)) with substantial improvement in DC conductivity at ambient and subambient temperatures when compared with literature reports. Conductivity variation with salt concentration, investigated within ±30 °C range, indicates an optimum conductivity of 5.6?×?10^?5 S cm^?1 at 30 °C for Ö/Li ~10 with a further lowering by one order at 0 °C and it remains unaltered at ?10 °C. Enhanced conductivity in this blend electrolyte, though lower than two copolymer counterparts, is attributed to very low glass transition temperatures of the host polymers. X-ray diffraction (XRD) and scanning electron microscopy (SEM) suggest an effective blending between the two polymers with an effective interaction between the Li salt and the blend polymer matrix. Raman spectroscopy results indicated that cation (Li⁺) coordination occurs at the C=Ö site in PEO out of the two electron-rich sites (i.e., CÖ and Si–Ö–Si) in the PEO–PDMS blend. The blend electrolytes are predominantly ionic (t _ion ~97 %).     

Solid solutions Li1+xV3O8 as cathodes for high rate secondary Li batteries

Following a preliminary investigation, Li/Li_1+xV₃O₈ cells have been examined. Using samples of low x content, up to 3 eq Li⁺ could be accepted both chemically and electrochemically by one mole of active material. Li⁺ is accomodated in the tetrahedral sites existing between the (V₃O₈)^(1+x)- layers. Li⁺ jumping from site to site is fast and permits high rate capabilities: at 10 mA/cm², 1.1 eq Li⁺ per mole could still be inserted. The structure does not show irreversible alterations upon extended lithiation, allowing long cycle lives to be achieved. Kinetic constraints limit the recovery of the full capacity of the first discharge at medium-high rates, but the second-discharge capacity declines slowly with cycle number.     

Study of the ion mobility in a Li0.03Na0.97Ta0.4Nb0.6O3 solid solution by raman spectra

We have studied ion mobility in a Li_0.03Na_0.97Ta_0.4Nb_0.6O₃ solid solution by its Raman spectra. It has been revealed that, as the temperature of the solution is increased to approach the point of the phase transition to a state with a high conductivity with respect to lithium, the lines with frequencies at 77, 118, and 142 cm^?1, which refer, respectively, to librations of oxygen octahedra Nb(Ta)O6 as a whole and vibrations of Li and Na ions in octahedra, considerably broaden, decrease in intensity, and smear into the wing of the Rayleigh line. Remaining lines are preserved in the spectrum. We have observed that the width of the line with a frequency of 118 cm^?1 depends exponentially on temperature, while the width of the line with a frequency of 142 cm^?1 changes linearly with it, which makes it possible to attribute to the line with the frequency of 118 cm^?1 to vibrations of Li⁺ cations, whereas the line with the frequency of 142 cm^?1 should be attributed to vibrations of Na⁺ cations in AO₁₂ cuboctahedra. The average lifetime of Li⁺ ions in equilibrium positions and the jump barrier have been estimated to be ～8 × 10^?12 s and ～20 kJ/mol, respectively. This agrees well with the data in the literature on measurements of electric conductivity.     

Vibrational,electrical, and structural properties of PVDF–LiBOB solid polymer electrolyte with high electrochemical potential window

Polyvinylidene difluoride (PVDF)–lithium bis(oxalato)borate (LiBOB) solid polymer electrolytes (SPEs) have been prepared by solution casting. The highest ionic conductivity achieved is 3.4610^?3 S cm^?1. Electrochemical potential window of the SPEs is found around 4.7 V. Interaction between PVDF and LiBOB is studied systematically. The changes of C–C, CF₂, and CH₂ vibration modes with an emerging shoulder are analyzed. At higher salt content, this shoulder becomes more prominent peak at the expense of CF₂ vibration mode. This suggests the possible Li⁺?F coordination. Deconvolution of IR spectra region from 1750 to 1850 cm^?1 has been carried out to estimate the relative percentage of free ions and contact ions. The finding is in good agreement with conductivity and XRD results. When more salt is present, the number of free ions percentage increases and the Full width at half-maximum (FWHM) of (110) plane is broadening. The Li⁺?F interaction breaks the folding patterns of polymer chain and enhances amorphousness domain.     

Improved luminescence of Y2MoO6:Eu3+ by doping Li+ ions for light-emitting diode applications

The photoluminescence (PL) property of Y₂MoO₆:Eu³⁺ doped with Li⁺ is investigated in this paper. The red luminescence of Eu³⁺ in Y₂MoO₆ lattice has greatly enhanced by codoping monovalent alkali metal ions Li⁺ into the lattice. The drastic increase in the luminescence intensity of Y_2?xLi_xMoO₆:Eu³⁺ originates from the reason that the Li⁺ ions may serve as a self-promoter for better crystallization to reduce the defect or as a lubricant for the complete incorporation of the Eu³⁺ ions into the Y₂MoO₆ host.     

Dominant Cr3+ centers in LiNbO3 under hydrostatic pressure

Low-temperature luminescence spectra of stoichiometric Cr: LiNbO₃ and of congruent Cr, Mg: LiNbO₃ were studied. Cr³⁺ impurity ions preferentially occupy Li⁺ sites (Cr_Li) in the LiNbO₃ crystal lattice, while Cr³⁺ ions substituting for Nb⁵⁺ ions (Cr_Nb) occur in addition to Cr_Li centers in codoped Cr, Mg: LiNbO₃ crystals. Application of a high hydrostatic pressure leads to a transformation of (dominant in concentration) Cr³⁺ centers from low-to high-crystal-field centers. Due to a strong pressure-induced blue shift of the ⁴ T ₂ state resulting in crossing with the ² E state, the replacement of the broad band ⁴ T ₂ → ⁴ A ₂ emission by a narrow R-line emission ² E → ⁴ A ₂ occurs in the luminescence spectra of the samples. This effect of level crossing was observed for the dominant Cr _Li ³⁺ and Cr _Nb ³⁺ centers at pressures which correlated well with estimations based on the ⁴ T ₂-² E energy gap (230 and 1160 cm^?1) and on the rate of their pressure-induced change (14.35 and 11.4 cm^?1/kbar, respectively).     

Vibrational spectrum of Li2B4O7 crystals

Polarized IR reflection spectra of Li₂B₄O₇ crystals are studied in a spectral range of 80–1600 cm^?1 and compared with their Raman spectra. Based on the results of the dispersion analysis of the spectra, the frequencies, damping constants, and oscillator strengths of all vibrations are determined. The inversion of frequencies of the longitudinal and transverse vibrations of the A ₁ and E symmetry in a range of 900–1150 cm^?1 is found. Based on the data thus obtained, the effective charges are calculated and the types of chemical bonds are analyzed for structural groups of the Li₂B₄O₇ crystal.     

Ion bombardment-induced decomposition of Li and Ba sulfates and carbonates studied by X-ray photoelectron spectroscopy

Radiation damage to the surfaces of lithium and barium sulfates and carbonates under 4 ke V Ar⁺ bombardment has been investigated by X-ray photoelectron Spectroscopy (XPS). Damage is readily observed at a dose of 1 × 10¹⁶ ions cm^?2 with saturation occurring over the range 2–8 × 10¹⁷ ions cm^?2. Both valence and core level XPS spectra indicate that, at the saturation dose, the basic sulfate and carbonate structures remain along with decomposition products. Both sulfur and carbon are preferentially lost from all four compounds and oxygen is preferentially lost from both Li compounds but not from the Ba compounds as a result of bombardment. The major decomposition products are the metal oxides with smaller quantities of carbides, sulfides, and SO_n^x?(n = 3,2,1) species.     

Localization of carbon atoms and extended defects in silicon implanted separately with C+ and B+ ions and jointly with C+ and B+ ions

The possibility to control the localization of implanted carbon in sites and interstices in silicon immediately during the implantation has been demonstrated. The formation of residual extended defects in silicon implanted separately with C⁺ and B⁺ ions and jointly with C⁺ and B⁺ ions has been shown. It has been found that the formation of residual defects can be suppressed due to annihilation of point defects at C atoms (the Watkins effect). The positive effect is attained if implanted carbon is localized over lattice sites, which is provided by its implantation with the effective current density of the scanning ion beam no lower than 1.0 μA cm^?2.     

Electrical and structural studies of a LiBOB-based gel polymer electrolyte

A series of gel polymer electrolytes (GPEs) containing lithium bis(oxalato)borate (LiBOB), propylene carbonate (PC), and ethylene carbonate (EC) have been investigated. Poly(ethylene oxide) (PEO) was used as the polymer. First, a series of liquid electrolytes was prepared by varying the Li:O ratio and obtained the best composition giving the highest conductivity of 7.1?×?10^?3 S cm^?1 at room temperature. Then, the PEO-based GPEs were prepared by adding different amounts of LiBOB and PEO into a mixture of equal weights of EC and PC (40 % of each from the total weight). The gel electrolyte comprises of 12.5 % of LiBOB, 7.5 % of PEO, 40 % of EC, and 40 % of PC gave the highest ionic conductivity of 5.8?×?10^?3 S cm^?1 at room temperature. From the DC polarization measurements, ionic nature of the gel electrolyte was confirmed. Fourier transform infrared (FTIR) spectra of electrolytes showed the Li⁺ ion coordination with EC and PC molecules. These interactions were exhibited in the peaks corresponding to ring breathing of EC at 893 cm^?1 and ring bending of EC and symmetric ring deformation of PC at 712 and 716 cm^?1 respectively. The presence of free Li⁺ ions and ion aggregates is evident in the peaks due to the symmetric stretching of O–B–O at 985 cm^?1.     

Super-protonic phase transition and fast ionic conductivity of Li+ in [Li0.2(NH4)0.8]2TeCl6

The differential scanning calorimetry diagram of [Li_0.2(NH₄)_0.8]₂TeCl₆ showed one anomaly at 526 K accompanied with a shoulder at 505 K.The conductivity plot exhibits two anomalies at 496 and 526 K, which characterize the beginning and the end of the crossing to superionic conductor state. The low temperature conduction is ensured essentially by Li⁺. A sudden jump confirms the presence of a superionic protonic transition related to the fast motion of Li⁺ and H⁺ ions. Above 526 K, the high temperature phase is characterized by high electrical conductivity (10^− 3 Ω^− 1 m^− 1) and low activation energy (E_a < 0.3 eV).The dielectric constant evolution as a function of frequency and temperature revealed the same anomaly.Transport properties in this material appear to be due to Li⁺ and H⁺ ions' hopping mechanism.     

Diffusion of Li ion in graphite cluster model at 800 K: a direct molecular orbital dynamics study

Using the hydrogen terminated planar cluster model, C₅₄H₁₈, the stabilization site of Li⁺ ion was determined by the unrestricted Hartree-Fock (UHF) AM1 energy gradient method. Six kinds of stabilization sites are considered, suggesting that the Li⁺ ion is rather stable at the two distinct sites in the bulk where the potential energy difference between them is 2.0 kcal/mol. For the Li⁺ ions stabilized at these two sites, the diffusion processes were simulated at 800 K through the direct molecular orbital dynamics procedure which was newly developed by one of the present authors. No jumping diffusion occurs with Li⁺ ions among the stabilization sites, but they diffuse along the outline of the cluster model with the fluctuations. It takes 2.0 ps for a Li⁺ ion to diffuse from the lower potential site to another equivalent site. On the other hand, it takes 0.7 ps to move from the higher potential site to the unstable circumference site composed of corner (armchair edge) carbon atoms. As the result, the diffusivity is approximated as 10⁻⁸-10⁻⁷ m²/s.     

A1Σu+-X1Σg+ and B1Πu-X1Σg+ fluorescence of 6Li2 and 6Li7Li excited by a krypton ion laser

The A¹Σ_u⁺-X¹Σ_g⁺ and B¹Π_u-X¹Σ_g⁺ fluorescence of the ⁶Li₂ and ⁶Li⁷Li molecules has been studied for all krypton ion laser lines (468.0–799.3 nm) which might be expected to excite such fluorescence. Only two A-X fluorescence series of ⁶Li₂ were found (one excited by 647.1 nm, and one by 752.5 nm). No A-X fluorescence series of ⁶Li⁷Li was found. Five B-X fluorescence series of ⁶Li₂ were found (one each excited by 468.0, 476.2, and 530.9 nm, and two by 568.2 nm). Four B-X fluorescence series of ⁶Li⁷Li were found (one each excited by 468.0 and 482.5 nm and two by 520.8 nm). Calculated Einstein A coefficients and lifetimes for these transitions are also given.     

Li3+ ion irradiation effects on ionic conduction in P(VDF–HFP)–(PC + DEC)–LiClO4 gel polymer electrolyte system

Swift heavy ion irradiation of P(VDF–HFP)–(PC + DEC)–LiClO₄ gel polymer electrolyte system with 48 MeV Li³⁺ ions having five different fluences was investigated with a view to increase the Li⁺ ion diffusivity in the electrolyte. Irradiation with swift heavy ion (SHI) shows enhancement of conductivity at lower fluences and decrease in conductivity at higher fluences with respect to unirradiated polymer electrolyte films. Maximum room temperature (303 K) ionic conductivity is found to be 2.2 × 10^− 2 S/cm after irradiation with fluence of 10¹¹ ions/cm². This interesting result could be ascribed to the fluence-dependent change in porosity and to the fact that for a particular ion beam with a given energy higher fluence provides critical activation energy for cross-linking and crystallization to occur, which results in the decrease in ionic conductivity. The XRD results show decrease in the degree of crystallinity upon ion irradiation at low fluences (≤ 10¹¹ ions/cm²) and increase in crystallinity at high fluences (> 10¹¹ ions/cm²). The scanning electron micrographs (SEM) exhibit increased porosity of the polymer electrolyte films after low fluence ion irradiation.     

New Li+ ion conductors in the system Li4SiO4−Li3AsO4

In the system Li₄SiO₄-Li₃AsO₄, Li₄SiO₄ forms a short range of solid solutions containing up to 14 to 20% Li₃AsO ₄, depending on temperature, and γ-Li₃AsO₄ forms a more extensive range of solid solutions containing up to ≈55% Li₄SiO₄. The Li₄SiO₄-Li₃AsO₄ phase diagram has been determined and is of binary eutectic character. The ac conductivity of polycrystalline samples was measured over the range 0 to at least 300°C for nine different compositions. The two solid solution series have much higher conductivity than the pure end-members; maximum conductivity was observed in the γ-Li₃AsO₄ solid solutions containing ≈40 to 55% Li₄SiO₄, with values of $\text{≈2×10}{}^{\mathrm{?6}}\text{Ω}{}^{\mathrm{?1}}\text{cm}{}^{\mathrm{?1}}$ at 20°C rising to ≈0.02 Ω^?1 cm^?1 at 300°C. These values are comparable to those found in the system Li₄SiO₄-Li₃PO₄. The variation with composition of the Arrhenius prefactor and activation energy has been interpreted in terms of the mechanisms of conduction. Li₃AsO₄ is a poor conductor essentially because the number of mobile Li⁺ ions is very small. This number, and hence the conductivity, increases dramatically on forming solid solutions with Li₄SiO₄, by the creation of interstitial Li⁺ ions. At ≈40 to 55% Li₄SiO₄, the number of mobile Li⁺ ions appears to be optimised. An explanation for the change in activation energy of conduction at ≈290°C in Li₄SiO₄ and at higher temperatures in Li₄SiO₄ solid solutions is given in terms of order-disorder of the Li⁺ ions.     

Ab initio calculations of endo-and exohedral C60 fullerene complexes with Li+ ion and the endohedral C60 fullerene complex with Li2 dimer

The results of ab initio Hartree-Fock calculations of endo-and exohedral C₆₀ fullerene complexes with the Li⁺ ion and Li₂ dimer are presented. The coordination of the Li⁺ ion and the Li₂ dimer in the endohedral complexes and the coordination of Li⁺ ion in the exohedral complex of C₆₀ fullerene are determined by the geometry optimization using the 3–21G basis set. In the endohedral Li⁺C₆₀ complex, the Li⁺ ion is displaced from the center of the C₆₀ cage to the centers of carbon hexa-and pentagons by 0.12 nm. In the Li₂ dimer encapsulated inside the C₆₀ cage, the distance between the lithium atoms is 0.02 nm longer than that in the free molecule. The calculated total and partial one-electron densities of states of C₆₀ fullerene are in good agreement with the experimental photoelectron and X-ray emission spectra. Analysis of one-electron density of states of the endohedral Li⁺@C₆₀ complex indicates an ionic bonding between the Li atoms and the C₆₀ fullerene. In the Li⁺C₆₀ and Li⁺@C₆₀ complexes, there is a strong electrostatic interaction between the Li⁺ ion and the fullerene.     

ß″-and ion-rich ß-alumina: Comparison of vibrational spectra and conductivity parameters

Single crystals of ß″-alumina containing Na⁺, K⁺, Ag⁺ and Tl⁺ ions are prepared and studied by Raman spectroscopy between 2 and 1000 cm^?1 in the 20–400 K temperature range. Far-infrared measurements are performed between 10 and 250 cm^?1. The Raman bands assigned to the spinel block vibrational modes are broad (Δv = 20 cm^?1); this reflects a high degree of disorder and can be related to stabilizing Mg²⁺ ions randomly distributed. In-plane cation vibrations are identified below 150 cm^?1 in infrared and Raman spectra. Potential barriers associated with this type of motion are discussed. The temperature dependence of the relevant low-frequency Raman spectra for K⁺ß″-alumina may be interpreted in terms of a small proportion of very mobile K⁺ ions. Tl⁺ spectra are discussed in terms of clusters. Finally, a comparison with literature results shows that the ß″ phase can be differentiated from t he ion-rich ß-alumina phase of the same composition.     

Schwingungsanregung von H2-Molekülen durch Zentralstoß mit Li+-Ionen

An apparatus is described for measuring the inelastic differential cross section for vibrational excitation in collisions of diatomic molecules with monoenergetic ions at laboratory energies between 10 and 50 eV. The method consists of measuring the time of flight of single ions with a time amplitude converter and displaying the results on a 100 channel pulse height analyzer. From the shift in the time of flight relative to that expected for elastic scattering the final state of the molecule excited in a single collision is identified. By studying only central collisions with almost zero impact parameter rotational excitation is strongly suppressed. Measured times of flight after collisions of monoenergetic Li⁺ ions with H₂ show that with increasing energy the most probable vibrational quantum jump increases from 0→1 to 0→2,0→3 etc. Contrary to the usual assumption of a small steric factor for vibrational excitation the results show that the inelastic cross section is larger than the elastic cross section. Using reported potential parameters the energy dependence of the most probable excited state is compared with the calculations of Secrest and Johnson for a one-dimensional collinear collision. The satisfactory agreement suggests that the steric factor is close to 1. From measurements at different scattering angles at 10 eV the integral inelastic cross section is found to be about 0.2 Ų corresponding to a differential cross section of 0.4 Ų/sr. Measured values of integral and differential total cross sections for Li⁺-He andLi⁺-H₂ are reported and compared with theory. Direct dissociation of D₂ by Li⁺ in the energy range from 25 to 55 eV was not observed, yielding an upper limit for the cross section of 4 · 10^?4 Ų/sr.