Increasing Li Content Research Articles

Microstructural evolution and hydrogen content and their effect on properties of TiB2/Al-Li-X composites with different Li contents

The content and proportions of the major solute elements in aluminum matrix composites are critical to the microstructure and properties of the material. This paper uses a stepwise method based on ultrasonic in-situ casting technology to prepare TiB2/Al-Li-X composites with different Li contents (0.5–3.0 wt%). The composites' microstructure morphology, precipitates, hydrogen content, and mechanical properties were tested and analyzed. The results showed that with the increase of Li content, the number of θ′ phases decreases, the number of δ′ phases increases, while the number of T1 phases increases and then decreases, and the TiB2 particles promote the precipitation of T1 phases at low Li content; meanwhile, the hydrogen content keeps increasing, and the grain size decreases and then increases. The increase of the T1 phase and the decrease of grain size enhance the strength of the composites, while the increase of δ′ phase and hydrogen content increase the hardness but decrease the plasticity. When the Li content is around 1.5 wt%, the grain size is minimized, the TiB2 particles are fine and dispersed, the yield strength reaches the maximum value of 166.9 MPa, and the mechanical properties are relatively balanced.

Synthesis and characterization of lithium-doped copper zinc tin sulfide (CZTS) thin films

The non-toxic nature and remarkable optoelectronic properties of kesterite (Cu2ZnSnS4 and CZTS) make CZTS a potential candidate for solar cell absorber layer material. Since alkali metal doping has shown a performance boost of active layers of solar cells, this work investigates the effects of significant lithium doping on sol-gel-produced CZTS thin films. CZTS- and lithium (Li)-doped CZTS thin films were prepared using the spin coating technique. The variation of structural, morphological, and optical properties of CZTS due to Li-doping has been studied by x-ray diffraction, scanning electron microscopy, and UV–visible spectroscopy techniques. All the synthesized LixCu2−xZnSnS4 (x = 0, 0.2, 0.4, 0.6) films showed fine crystallinity with average crystallite sizes of 4.745, 6.013, 6.255, and 6.404 nm, respectively. The average grain size decreases from 0.336 to 0.310 µm via increasing Li concentration. The inclusion of Li increased the bandgap energy ranges from 1.5 to 1.808 eV. The Li0.6Cu1.4ZnSnS4 thin showed the highest absorption coefficient of 3.505 × 104 cm−1 among all the prepared thin films. A high optical conductivity over 1014 s−1 was observed for CZTS, which further increased with an increased Li concentration. The synthesized structures showed enhanced characteristics suitable for solar cell application.

Electrocaloric, thermal and structural properties of Ba1−xLixTi0.975V0.025O3±δ (0 ≤ x ≤ 0.05) ceramics

The present work reveals the electrocaloric, structural, thermal, and other physical properties of Ba1−xLixTi0.975V0.025O3±δ (0 < x ≤ 0.05) ceramics synthesized via the solid-state chemical reaction method. X-ray studies reveal the presence of BaTiO3 phase in all the samples, wherein the phase fraction of BaTiO3 decreases with increasing Li content. Besides this, the replacement of lighter weight Li-atoms in place of Ba-atoms increases porosity and consequently decreases the density of the samples. However, the molar volume increases while inter-ionic distance decreases due to the small size of Li-atoms as compared with Ba-atoms. In this series, the sample with x = 0.05 exhibited a maximum change in entropy i.e., ΔS = 0.728 JK−1 kg−1 and the largest change in temperature i.e., ΔT = 0.422 K at 90 °C with the application of a 20 kV/cm electric field. Moreover, the x = 0.05 ceramic has the largest value of specific heat i.e., 626.59 JK−1 kg−1 as discovered during DSC investigations. In the present study, Li- and V- are attributing to good sintering and Li- in place of Ba- is enhancing electrocaloric properties in BaTiO3 ceramic.

Lithium isotopic systematics and numerical simulation for highly-fractionated granite-pegmatite system: Implications for the pegmatite-type rare-metal mineralization

Lithium (Li) isotope behavior during fractionation of highly-evolved granitic pegmatites and associated rare metal mineralization remains unclear, especially concerning the relative importance of magmatic versus metasomatic processes. In this study, we investigated the geochemistry and Li isotopes of the giant Renli-Chuanziyuan lithium-niobium-tantalum (Li-Nb-Ta) deposit in the Mufushan batholith (South China). We found that muscovite granite in the Mufushan complex can be divided into two groups (high-Li and low-Li). δ7Li value of the high-Li and low-Li group increases and decreases, respectively, with increasing Li content, which is likely resulted from fractional crystallization and/or magmatic volatile phase (MVP) exsolution. The MVP exsolution began with the solidification of muscovite granite, as evidenced by the zoned micas. The Li isotope fractionation, modeled by Rayleigh distillation during MVP exsolution, is consistent with the δ7Li value of Li-poor pegmatite, indicating that MVP exsolution is related to the pegmatite formation.The Mufushan Li-poor and Li-rich pegmatites have very high and low δ7Li value, respectively. Based on the Δ7Li(bulk-mica) value and numerical simulation, we suggest that the pegmatite formation at Mufushan could be linked to extensive MVP accumulation, while the different Li elemental and isotopic compositions of the two types of pegmatite are probably caused by MVP migration. In fact, published granite-pegmatite data worldwide also show negative Li vs. δ7Li correlation, indicating that such MVP exsolution, accumulation and migration are probably a common phenomenon for evolution of granitic pegmatite. Therefore, the different Li isotopes and Li-Rb-Cs proportion of Li-poor and Li-rich pegmatites indicate that MVP exsolution, migration and accumulation are key to rare metals enrichment and distinguish various types of rare-metal mineralization (Li and Nb-Ta).

Influence of tetragonal/cubic phase composition on the total ionic conductivity of Li3xLa2/3−xTiO3

Lithium lanthanum titanate (Li3xLa2/3−xTiO3, abbreviated as LLTO, where x = 0.08, 0.1, 0.12, 0.14, 0.16, and 0.167) is prepared using a conventional solid-phase method, and its crystal structure, phase composition, microstructure, and electrical properties are investigated. Experimental results indicate that when the Li content is low (x = 0.8), there exist tetragonal, cubic, and orthogonal phases in LLTO. As the Li content increases (x ≥ 0.1), the orthogonal phase disappears, and there are changes in the phase composition of tetragonal and cubic phases. When the occupancy rates of Li and La are low, the number of A-site vacancies increases, as does the electrical conductivity of LLTO. At room temperature, the ionic conductivity of LLTO increases and then decreases. The Li0.30La0.56TiO3 ceramic electrolyte exhibits the highest total ionic conductivity of 7.22 × 10−5 S/cm, a minimum activation energy of 0.31 eV, and an electrical conductivity of 6.26 × 10−11 S/cm. This paper provides a theoretical basis for subsequent research on solid Li3xLa2/3−xTiO3 electrolytes.

Operando Nanomechanical Mapping of Silicon Thin Film Electrode during the First Lithiation and Delithiation Investigated By Bimodal Atomic Force Microscopy

Si is emerging as one of the most prospective anode materials for all-solid-state Li-ion batteries due to its extremely high theoretical capacity density of 4200 mAh g-1 and relatively negative potential for lithiation/delithiation. Towards its widespread use, controlling severe volume expansion/contraction during lithiation/delithiation is a challenge because it may cause cracking, fracture, and pulverization that negatively influence the cycle performance and rate capability of the cells [1]. Such mechanical event is induced by the change in the lattice structure due to the formation of LixSi and successive increasing/decreasing of Li content x in LixSi [2].Bimodal atomic force microscopy (AFM) offers quantitative mapping of nanoscale mechanical property, simultaneously with surface topography imaging [3]. Our group previously applied this technique to the cross-section of a composite electrode consist of active materials, binders, conductive additives, and deposited electrolyte solution and successfully demonstrated nanomechanical mapping [4]. Here, we develop an operando bimodal AFM system to track Young’s modulus changes of electrode materials in an all-solid-state battery configuration during the lithiation and delithiation reactions in real-time.A cell in a Cu/Si/LLZT/In/Li configuration was fabricated as follows; a 3 µm-thick Si thin-film and a 100 nm-thick Cu layer were sputter-deposited on one side of Li6.6La3Zr1.6Ta0.4O12 (LLZT) solid electrolyte, an In layer was sputter-deposited on the other side of LLZT, the Cu/Si/LLZT/In sample was milled with an Ar-ion beam to yield a flat and smooth cross-section suitable for AFM analysis, and then a 50 µm-thick Li metal foil was combined with the pre-coated In thin layer. Operando nanomechanical mapping was performed by mounting the cross-section-exposed cell in the custom-made sample holder coupled with a potentiostat for bias applications, in an Ar-filled glove box to prevent any atmospheric influences.Electrochemical lithiation and delithiation were carried out within a potential window of 0.01-1.20 V vs. Li/Li+. Electrochemical characterization indicated that the capacities of the Si electrode for the first lithiation and delithiation are 3300 and 1833 mAh g-1, respectively. These capacities are equal to the formation of Li3.46Si after the first lithiation of the pristine Si and Li1.54Si after the successive delithiation from Li3.46Si. Throughout the lithiation, the averaged Young’s modulus of Si electrode decreased due to the formation of LixSi and increase in the Li content x in LixSi. In the initial stage of lithiation, it drastically decreased because LixSi was formed by the lithiation of pristine Si. Then, it moderately decreased with increasing Li content x in LixSi. Unfortunately, the Young’s modulus maps were only recorded until the formation of Li1.54Si because the successive delithiation was not completed possibly due to the phase transformation of crystalline LixSi to amorphous LixSi [5], which may cause a significant mechanical strain inside the thin film. The measured Young’s modulus values were consistent with those obtained by first principle calculation [6]. Further details are given at the presentation.

Structural characterisation and degradation of Mg–Li thin films for biodegradable implants

Freestanding thin films of Mg–Li (magnesium–lithium) alloys with a Li mass fraction between 1.6% (m/m) and 9.5% (m/m) were prepared and studied with respect to their structure and degradation properties. With increasing Li content, the microstructure deviates from hexagonal Mg–Li with strict columnar growth and preferred orientation, and additional cubic Mg–Li and Li2CO3 occur. The corrosion rate was measured in Hanks’ balanced salt solution by potentiodynamic polarisation and weight loss measurements to investigate biodegradation. Influences of the orientation, phase and protective layer formation lead to an increase in corrosion from 1.6 to 5.5% (m/m) from 0.13 ± 0.03 to 0.67 ± 0.29 mm/year when measured by potentiodynamic polarisation but a similar corrosion rate for 9.5% (m/m) and 3% (m/m) of Li of 0.27 ± 0.07 mm/year and 0.26 ± 0.05 mm/year.

Comparison of microstructure, mechanical property, and degradation rate of Mg-1Li-1Ca and Mg-4Li-1Ca alloys.

Mg-1 wt.% Li-1 wt.% Ca (LX11) and Mg-4 wt.% Li-1 wt.% Ca (LX41) alloys share the same hexagonal closed-packed crystalline structure. However, the differences in microstructure, mechanical properties, and degradation rates between the two alloys are not well understood. Hereby, the above three aspects of LX11 and LX41 alloys were studied via optical microscopy, tensile tests, and electrochemical polarization and electrochemical impedance spectroscopy, together with hydrogen evolution. The concentration of the released Mg2+, Ca2+, and Li+ ions was analyzed using a flame atomic absorption spectrophotometer. Results demonstrated that the LX11 alloy was composed of finer α-Mg grains, fewer twins, and smaller volume fractions of the intermetallic phases Mg2Ca than the LX41 alloy. The increasing Li concentration generated a weak decrease in the yield strength of the Mg-Li-Ca alloys, a remarkable increase in elongation to failure, and a stable ultimate tensile strength. The LX11 alloy had better corrosion resistance than the LX41 alloy. The release rate of the cations (Mg2+, Ca2+, and Li+) varied significantly with time. The release rate of metallic ions in Hank's solution cannot reflect the true corrosion rate of Mg-Li-Ca alloys due to the formation of the precipitated corrosion products and their difference in solubility. The dealloying corrosion mechanism of the Mg2Ca phase in Mg-Li-Ca alloys was proposed.

Partitioning and isotopic fractionation of Li between mineral phases and alkaline to calc-alkaline melts of explosive and effusive eruptions

Evaluating the lithium (Li) budget of alkaline to calc-alkaline melts and their co-existing mineral phases is crucial to understanding which magmatic or post-eruptive processes can influence the Li contents and isotopic compositions of volcanic deposits. This is also important to be able to better constrain how economically relevant Li deposits form. The lithium contents of many different eruptions from different tectonic settings (intraplate, subduction zone, extensional environment) and cooling environments (quenched, quickly cooled and slowly cooled) were studied by combining new and literature data that were obtained using LA-ICP-MS. We found that the Li concentrations in melt inclusions and re-entrants are independent of tectonic setting (hotspot, subduction zone and rifting) and rarely exceed 100 ppm. When melt inclusions are re-homogenised the Li concentration increases which can lead to the overestimation of the Li budget of a magma.The highest Li concentrations in the alkaline suite of samples were found in groundmass glass (reaching up to 318 ppm). The Li contents in the co-existing mineral phases decrease in the following order: biotite (0.8–99.3 ppm), plagioclase (0.9–25.1 ppm), clinopyroxene (0.6–31.0 ppm) and sanidine (0.5–38.7 ppm). The highest Li concentrations in the calc-alkaline suite of samples were found in the biotite crystals (10.2–2314 ppm) followed by the groundmass glass (2.1–176 ppm). The Li contents are lower in the other mineral phases, from plagioclase (1.4–35.0 ppm), quartz (3.2–21.1 ppm), olivine (1.0–16.3 ppm), sanidine (0.3–8.1 ppm) to clinopyroxene (0.7–21.8 ppm). The Li concentrations in groundmass glass and co-existing crystal phases are independent of the tectonic setting but appear to be more closely related to their cooling environment. To evaluate the influence of the different cooling environments the Li isotopic compositions (per mil deviation of 7Li/6Li ratio relative to L-SVEC reference material) of different eruptions were also determined. The Li isotopic compositions of groundmass glass and mineral phases reveal a range in δ7Li composition spanning up to 6 ‰ for alkaline samples and >10‰ between bulk sample and mineral phases for calc-alkaline samples. The cooling environment of the samples has a large impact on the Li isotopic compositions of the mineral phases with only quartz seemingly unaffected. Rapidly quenched samples may retain their magmatic δ7Li compositions or will only experience small amounts of diffusional overprinting (e.g., by degassing) whereas slowly cooled samples will experience a prolonged diffusional exchange between minerals and matrix overprinting their magmatic δ7Li compositions.The Li inventory in quartz crystals may be influenced by the tectonic setting and water concentration in the crystals. To further assess the influence of tectonic settings on Li behaviour we used a large data set which is based on the 13 alkaline to calc-alkaline eruptions from different tectonic settings and calculated the apparent partition coefficients (Kds) between groundmass glass and co-existing mineral phases. Biotite crystals (alkaline systems) return the highest Kds (subduction-extensional setting: 0.01–0.57, oceanic hotspot: 0.17–2.65) whereas sanidine crystals yield the lowest Kds. Sanidines from the subduction-extensional setting (alkaline trend) have the lowest Kds (0.01–0.07; one outlier ranging from 0.02 to 0.24), followed by the oceanic hotspot setting (alkaline trend, 0.02–0.09) and the extensional setting (calc-alkaline trend; 0.01–0.15). Plagioclase crystals from the subduction-extensional setting (alkaline trend) yield Kds between 0.01 and 0.29, crystals from subduction zone settings (0.06–0.81) and extensional settings (0.09–0.50) have larger ranges in their Kds. The clinopyroxene crystals from the subduction zone settings (calc-alkaline trend) have the largest range in Kds (0.03–0.99), followed by the oceanic hotspot setting (alkaline trend, 0.06–0.48) and subduction-extensional setting (alkaline trend, 0.01–0.22). Quartz crystals (only from the calc-alkaline trend) from subduction zone settings have lower Kds (0.09–0.13) compared to the extensional settings (Bishop Tuff: 0.14–0.28; Caetano Tuff: 0.73–0.94). The wide variety of processes that can affect final Li abundances in melt and crystals (degassing, scavenging into fluids, intra-crystal diffusion, hydration of glasses) makes estimating the partition coefficients particularly difficult and results in the wide ranges observed here. Targeted experimental work would thus help to better constrain the behaviour of Li in alkaline compositions.

Preparation, Properties, and Applications of Near Stoichiometric Lithium Tantalate Crystals

Lithium tantalate crystal is widely used in optical devices, infrared detectors and surface acoustic wave devices because of its excellent piezoelectric, acousto-optic and nonlinear optical properties. The Li content of near stoichiometric lithium tantalate (NSLT) crystal is higher than that of congruent lithium tantalate (CLT) crystal. Therefore, the performance of NSLT crystal is better than that of CLT crystal in some aspects. This article reviews the physical properties, preparation methods and current research status in acoustics and optics of NSLT crystals. It also looks forward to the improvement of NSLT crystal preparation methods and their applications in surface acoustic wave (SAW) filters and optics. With the increase of Li content, the acoustic performance of NSLT crystals is expected to be comprehensively improved, achieving the application of SAW filters in 5G communication.

Effects of Li content on microstructure evolution and mechanical properties of squeeze-cast Al-5Cu-xLi alloy assisted with ultrasonic treatment

In this study, a new squeeze-cast Al-5Cu-xLi-0.5Mn-0.3Mg-0.15Ti (x = 0.3, 0.6, 0.9, 1.2 wt%) alloy (Al-5Cu-xLi alloy for short) was prepared with ultrasonic treatment (UT), and the effects of UT and Li content on the microstructure evolution and mechanical properties of Al-5Cu-xLi alloy were investigated. Unlike other aluminum alloys, UT applied to aluminum-lithium alloys can bring about significant degassing effects in addition to grain refinement and homogenization, which is beneficial for the high strength and toughness of Al-5Cu-xLi alloy. With the increase of Li content from 0.3 wt% to 1.2 wt%, the average grain size remains unchanged at first, and then increases significantly. Interestingly, the average size of α-Al grains is 30% smaller than that of Al-5Cu-0Li alloy (without Li element) after adding only 0.3 wt% of Li element, while the ultimate tensile strength (UTS), yield strength (YS) and elongation are increased by 11.3%, 15.6% and 26.9%, respectively. The optimal comprehensive mechanical properties are obtained in Al-5Cu-0.6Li alloy, which exhibits 300 MPa in UTS, 190 MPa in YS and 16.7% in elongation. However, by further increasing the Li content, the strength of the Al-5Cu-xLi alloy remains almost unchanged, while its elongation decreases significantly (but still more than 13.5%), due to grain coarsening and slight compositional segregation.

Effect of Li Content on the Microstructure and Mechanical Properties of as-Homogenized Mg-Li-Al-Zn-Zr Alloys

The microstructure and mechanical properties of as-homogenized Mg-xLi-3Al-2Zn-0.2Zr alloys (x = 5, 7, 8, 9, 11 wt.%) were studied. As the Li content increased from 5 wt.% to 11 wt.%, the alloy matrix changed from the α-Mg single-phase to α-Mg+β-Li dual-phase and then to the β-Li single-phase. Homogenized With the increase in Li content, the alloy strength decreased while the elongation increased, and the corresponding fracture mechanism changed from cleavage fracture to microvoid coalescence fracture. This is mainly attributed to the matrix changing from α-Mg with hcp structure to β-Li with bcc structure. Additionally, the increase in the AlLi softening phase led to the reduction of Al and Zn dissolved in the alloy matrix with increasing Li content, which is one of the reasons for the decrease in alloy strength.

Effect of Li+ concentration on the structural and optical properties of chemically synthesized ZnS nanoparticles

ZnS nanoparticles (NPs) with different concentrations of Li-doping (0, 2.5, 4.5, 6.5, and 10.5 %) were synthesized by the co-precipitation method. Crystalline structure, surface morphologies, and optical properties were studied in detail. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) confirmed the cubic phase of un-doped and Li doped-ZnS NPs. Scanning electron microscopy (SEM) and HRTEM images showed that un-doped and Li-doped ZnS NPs contain agglomerated particles, and agglomeration is increased by increasing Li-doping. Different vibration modes are observed in a Fourier transform infrared spectrophotometer (FTIR) analysis. Defects are observed in the photoluminescence spectra (PL) of un-doped and Li-doped ZnS NPs, and a dominant green-orange transition is observed. Absorption studies using UV–vis spectroscopy reveal a quantum confinement effect for un-doped and Li- doped ZnS NPs. The direct band gap energy (Egp) increased with increasing Li concentration in the range of 3.728–3.875 eV.

300 MPa grade highly ductile biodegradable Zn-2Cu-(0.2-0.8)Li alloys with novel ternary phases

Although a few high-strength biodegradable Zn alloys with yield strengths (YSs) over 300 MPa in rolled state have been developed, their elongations (ELs) are generally less than 30%. This study developed rolled Zn-2Cu-xLi (x = 0.2 wt.%, 0.5 wt.%, 0.8 wt.%) alloys with YSs of 316–335 MPa and ELs of 44%–61%. Three-dimensional atom probe (3DAP) and time of flight secondary ion mass spectrometry (TOF-SIMS) were employed to characterize Li distribution. Three kinds of Zn-Cu-Li ternary phases are identified, which are blocky ε′-(Cu0.5, Li0.5)Zn4, blocky β′-(Li0.9, Cu0.1)Zn4, and small round γ particles with high Li content in the annealed state. Other identified phases are Zn, β-LiZn4, and ε-CuZn4 phases. With the increase of Li content in the alloys, ε′ phase with 6.50 at.% Cu transforms into β′ phase with 2.12 at.% Cu, i.e., the average level in the alloys. Within ε′ phase, there exist nano-scale Li clusters and ε phase, resulting in ε′/ε structure. Dense Zn laths precipitate from β′ phase, resulting in β′/Zn lamellar structure. The lamellar structure is the matrix of Zn-2Cu-0.8Li and leads to near-isotropic plasticity. Electrochemistry tests show that degradation rates fall in the range of 153–196 μm/year, which decrease with Li content. All the alloys exert positive effects on the growth of MC3T3-E1 cells with 10% extract. This research reveals how microstructure evolves in Zn-2Cu-xLi alloys, which lays the foundation for their future applications.

Effect of Li substitution on the structural, magnetic, and electrical properties of nanocrystalline LixNi0.6-2xZn0.4Fe2+xO4

Nanocrystalline LixNi0.6–2xZn0.4Fe2+xO4 (where x = 0.00, 0.05, 0.10, 0.15, and 0.20) were prepared by the auto-combustion synthesis route. Each composition was sintered at different sintering temperatures, Ts, (1100–1250 °C) for 5 h. The optimum Ts for each composition was selected based on their maximum bulk density. For the first three compositions (x = 0.00, 0.05, and 0.10), the optimum Ts was 1200 °C, and for x = 0.15, Ts = 1175 °C, and for x = 0.20 Ts = 1150 °C. The Rietveld refinement of X-ray diffraction (XRD) patterns confirmed the monophasic formation of cubic spinel structure. The lattice constant was found to decrease (8.3821–8.3706 Å) slightly, complying with Vegard's law. The crystallite size calculated using Scherrer formula varied from 53 to 59 nm. However, the microstructural study showed that the average grain size has enlarged (0.53–1.39 μm) with substituting Li content up to x = 0.10. The real part of initial permeability increased up to x = 0.10, and the maximum value was 52 (at 1 MHz). The saturation magnetization, Ms, enhanced with increasing Li content, obeying the Globus model. The maximum Ms obtained for Li0.1Ni0.4Zn0.4Fe2.1O4 was 76 emu/g. The dielectric constant exhibited dispersive behavior with changing frequency. At lower frequency (<105 Hz), the dielectric constant was high, but fell down with increasing frequency. The ac conductivity and electric modulus remained low at lower frequency (<105 Hz), but ascended with increasing frequency. In contrast, the complex impedance spectra followed the reverse trend with changing frequency.

Effects of Li content on stability, electronic and Li-ion diffusion properties of Li&lt;sub&gt;3&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;La&lt;sub&gt;(2/3)–&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;†&lt;sub&gt;(1/3)–2&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;TiO&lt;sub&gt;3&lt;/sub&gt; surface

Li&lt;sub&gt;3&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;La&lt;sub&gt;(2/3)–&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;†&lt;sub&gt;(1/3)–2&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;TiO&lt;sub&gt;3&lt;/sub&gt;(LLTO) is a promising solid-state electrolyte for Li-ion batteries. We study the effect of Li content on the stability, electronic and Li-ion diffusion properties of LLTO surface based on first-principles and molecular dynamics simulations. We consider both Li-poor and Li-rich LLTO surfaces. The results show that La/O/Li-terminated LLTO (001) is the most stable crystal surface. Further, LLTO (001) surface gives better stability when Li content is 0.17, 0.29, and 0.38 for Li-poor phase, while 0.33, 0.40, and 0.45 for Li-rich phase . Electronic structure calculations infer that in both Li-poor and Li-rich LLTO(001) surfaces there occurs the transition from conductor to semiconductor with the increase of Li content. Besides, we find that Li-ion always keeps a two-dimensional diffusion path for different Li content. As Li content increases from 0.17 to 0.38 for Li-poor LLTO (001) surface, Li-ion diffusion coefficient increases gradually and Li-ion diffusion barrier decreases from 0.58 eV to 0.42 eV. Differently, when Li content increases from 0.33 to 0.45 for Li-rich LLTO(001) surface, it does not follow a monotonic trend for diffusion coefficient nor for diffusion barrier of Li-ion. In this case, Li-ion diffusion coefficient is the largest and Li-ion diffusion barrier is the lowest (0.30 eV) when Li content is 0.40. Thus, our study suggests that by varying Li content, the stability, band gap, and Li-ion diffusion performance of LLTO (001) can be changed favorably. These advantages can inhibit the formation of lithium dendrites on the LLTO (001) surface.

Self-diffusion in polycrystalline Li1+x Ti2-x Al x (PO4)3 (0.2 ≤ x ≤ 0.4) samples followed by 7Li PFG (pulse field gradient) NMR spectroscopy.

Short and long range lithium motions in powder Li1+x Ti2-x Al x (PO4)3 (LTAP) NASICON compounds prepared by ceramic (x = 0.2 and 0.4) and sol-gel (x = 0.3 and 0.4) routes are discussed. ND diffraction and MAS-NMR spectroscopy were previously used to investigate structural features of these compounds. In particular, Fourier map differences showed that the amount of Li atoms allocated at M3 increases at the expense of M1 sites when the Li content increases. In this work, PFG-NMR results show that diffusion coefficients rise with the amount of lithium and temperature. The restricted diffusion inside NASICON particles is compared with "free" diffusion processes. At 300 K, diffusion coefficients D PFG ∼ 5 × 10-12 m2 s-1 have been deduced in ceramic x = 0.2 and 0.4 samples, decreasing with diffusion time Δ used in PFG experiments. In sol-gel samples, diffusion coefficients are near those of ceramic samples, but decrease faster with diffusion Δ times, as a consequence of the Li confinement inside sub-micrometric crystallites. The NMR spin-echo signal displays minima at specific q(γgδ) values that are related to the crystallite size. From R dif ∼ q m -1 distances, calculated from the position of minima, and from diffusion coefficients deduced for high Δ values, the mean crystallite size was estimated. Finally, from the temperature dependence of conductivity and diffusion coefficients, the activation energy and charge carriers concentrations were determined.

Structural, optical, and antibacterial properties of Li-doped ZnO nanoparticles synthesized in water: evidence of incorporation of interstitial Li

The mode of incorporation of lithium (Li) (as substitution or interstitial position) in zinc oxide (ZnO) has its own importance as far as the potential applications of Li-doped ZnO nanoparticles (NPs) are concerned. Fabrication of p-type ZnO-based semiconductors as well as defect engineering-based applications demand substitution of Zn2+ by Li+. However, doping of ZnO by Li with interstitial positions can play an important role in controlling different properties of it. In the present study, we report the successful doping of Li in ZnO NPs up to a Li concentration of 10 mol% employing a simple wet chemical precipitation method in water. Up to a Li concentration of 8 mol%, doping by substitution of Li to the Zn sites has been observed. However, for 10 mol% of Li concentration, doping by incorporation of interstitial sites in addition to the substitution has been confirmed through complementary characterization techniques. The effects of interstitial Li in ZnO on structural, optical, and antimicrobial properties have been studied in detail systematically. For all the cases (structural, optical, and antimicrobial), the properties of Li-doped ZnO NPs have been changed reversibly in the ZnO NPs after the incorporation of interstitial sites by Li as compared to the substitution of Li. For example, the microstrain, band gap, and antimicrobial activity have been found to increase with the increase in Li concentration up to 8 mol%. However, the microstrain, band gap, and antimicrobial activity are found the decrease for 10 mol% of Li as compared to 8 mol% of Li. This study indicated that the different properties of Li-doped ZnO NPs can be controlled suitably as per the requirements for the practical applications of ZnO-based materials.

LixAg1–xGaSe2: Interplay Between Lithium and Silver in Mid‐Infrared Nonlinear Optical Chalcogenides

AbstractAgGaSe2 and LiGaSe2 are two famous mid‐infrared nonlinear optical (NLO) materials with similar chemical formula but different structural symmetry. The former material has relatively larger NLO effect and birefringence but rather small energy band gap, while the latter is the opposite. Aiming at achieving a good balance of NLO properties, here the substitution between silver and lithium ions on the evolution of structural and optical properties in a new series of LixAg1–xGaSe2 crystals is systematically investigated. It reveals that, with the increase of Li content, LixAg1–xGaSe2 almost keeps the same tetragonal symmetry with AgGaSe2 until x ≈ 0.9. The NLO effects and birefringence values vary with respect to x with the largest variation at x = 0.8–0.9. The optimal combination of birefringence (0.03–0.025) and nonlinear parameters (26–30 pm V−1) is achieved at x = 0.4–0.5. As the energy band gap increases with the increase of x, the maximal value of 2.2 eV for chalcopyrite structure suggests that the laser‐induced damage threshold of LixAg1–xGaSe2 would be as large as five‐fold of AgGaSe2. This study provides a good example to show that the rational substitution between Li and Ag can significantly improve the balance of NLO properties in chalcogenides.

Structure and electrochemical properties of CNT-supported Li-Ti-O anode material for Li-ion battery

We investigated the structural and electrochemical properties of Li-Ti-O (LTO) and carbon nanotube (CNT)-added LTO for anode material in secondary Li-ion batteries using various techniques. The study focused on elucidating the effects of the microstructural evolution in LTO and the CNT addition on battery functionality. For all the tested compositions of LTO ([Li]/[Ti] = 0.9, 1.0 and 1.22), the system is fully oxidized to comprise a mixed-phase having Li4+2δTi5O12+δ (δ’s are approximately 0.14, 0.25, and 0.65, respectively) and Li2TiO3 structures. The results of the half-cell tests show a decrease in charge/discharge capacity with increasing [Li]/[Ti] ratio, and the detailed structural and chemical analyses unequivocally reveal that the such degradation in the electrochemical property originates mainly from the increase of Li content (δ). Meanwhile, after adding CNT, the Li capacity becomes greatly increased while the LTO composition and the redox kinetics do not change significantly. The origin of the improved specific capacity is associated with the formation of micron-sized structures at the surface of the LTO particles. Thereby we demonstrate that surface engineering via the CNT addition is a promising way to improve the performance of the LTO-based anode material.