Relationship between lithium content and ionic conductivity in the Li5+2xLa3Nb2−xScxO12 system (original) (raw)
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Journal of Power Sources, 2011
We report the effect of Y substitution for Nb on Li ion conductivity in the well-known garnet-type Li 5 La 3 Nb 2 O 12. Garnet-type Li 5 La 3 Nb 2−x Y x O 12−ı (0 ≤ x ≤ 1) was prepared by ceramic method using the high purity metal oxides and salts. Powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), 7 Li nuclear magnetic resonance (Li NMR) and AC impedance spectroscopy were employed for characterization. PXRD showed formation of single-phase cubic garnet-like structure for x up to 0.25 and above x = 0.25 showed impurity in addition to the garnet-type phases. The cubic lattice constant increases with increasing Y content up to x = 0.25 in Li 5 La 3 Nb 2 − x Y x O12−␦ and is consistent with expected ionic radius trend. 7 Li MAS NMR showed single peak, which could be attributed to fast migration of ions between various sites in the garnet structure, close to chemical shift 0 ppm with respect to solid LiCl and which confirmed that Li ions are distributed at an average octahedral coordination in Li 5 La 3 Nb 2 − x Y x O 12 − ı. Y-doped compounds showed comparable electrical conductivity to that of the parent compound Li 5 La 3 Nb 2 O 12. The x = 0.1 member of Li 5 La 3 Nb 2 − x Y x O 12 − ı showed total (bulk + grain-boundary) ionic conductivity of 1.44 × 10 −5 Scm −1 at 23 • C in air.
Ionics, 2007
The stoichiometry range and lithium ion conductivity of Li 5+x Ba x La 3−x Ta 2 O 12 (x=0, 0.25, 0.50, 1.00, 1.25, 1.50, 1.75, 2.00) with garnet-like structure were studied. The powder X-ray diffraction data of Li 5+x Ba x La 3−x Ta 2 O 12 indicated that single phase oxides with garnet-like structure exist over the compositional range 0≤x≤1.25; while for x= 1.5, 1.75 and 2.00, the presence of second phase in addition to the major garnet like phase was observed. The cubic lattice parameter increases with increasing x and reaches a maximum at x=1.25 then decreases slightly with further increase in x in Li 5+x Ba x La 3−x Ta 2 O 12. The impedance plots of Li 5+x Ba x La 3−x Ta 2 O 12 samples obtained at 33°C indicated a minimum grain-boundary resistance (R gb) contribution to the total resistance (R b +R gb) at x=1.0. The total (bulk+ grain boundary) ionic conductivity increases with increasing lithium and barium content and reaches a maximum at x= 1.25 and then decreases with further increase in x in Li 5+x Ba x La 3−x Ta 2 O 12. Scanning electron microscope investigations revealed that Li 6.25 Ba 1.25 La 1.75 Ta 2 O 12 is much more dense, and the grains are more regular in shape. Among the investigated compounds, Li 6.25 Ba 1.25 La 1.75 Ta 2 O 12 exhibits the highest total (bulk+grain boundary) and bulk ionic conductivity of 5.0×10 −5 and 7.4×10 −5 S/cm at 33°C, respectively.
Applied Physics A-materials Science & Processing, 2008
We report systematic studies on the transport properties by varying the lithium oxide content of the garnet-based solid electrolyte Li5+xBaLa2Ta2O11.5+0.5x (x=0, 0.50, 0.75, 1.00, 1.25, 1.50, 1.75, 2.00) for understanding the ionic conductivity dependence on the crystal lattice parameter and carrier concentration. Powder X-ray diffraction data of Li5+xBaLa2Ta2O11.5+0.5x (x=0, 0.50, 0.75, 1.00, 1.25, 1.50, 1.75, 2.00) indicate the existence of the garnet-like structure for any of the compositions. The cubic lattice parameter was found to increase with increasing x and reaches a maximum at x=1.00, then decreases slightly with a further increase in x. Impedance measurements obtained at 50 °C indicate a maximum of the grain-boundary resistance (Rgb) contribution to the total resistance (Rb+Rgb) at x=0.0 and a considerable decrease with increase in lithium concentration. The total (bulk + grain-boundary) and bulk ionic conductivity increase with increasing lithium content and reach a maximum at x=1.00 and then decrease slightly with further increase in x. Among the investigated compounds, Li6BaLa2Ta2O12 exhibits the highest total (bulk + grain-boundary) and bulk ionic conductivity of 1.5×10-4 and 1.8×10-4 S/cm at 50 °C, respectively. The results obtained in the present investigation of the Li5+xBaLa2Ta2O11.5+0.5x (x=0–2) series clearly revealed that the lithium content plays a major role in decreasing the grain boundary resistance contribution to the total resistance and also in increasing the ionic conductivity of the garnet-like compound.
Novel Fast Lithium Ion Conduction in Garnet-Type Li 5 La 3 M 2 O 12 (M = Nb, Ta)
Journal of the American Ceramic Society, 2003
Lithium metal oxides with the nominal composition Li 5 La 3 M 2 O 12 (M ؍ Nb, Ta), possessing a garnetlike structure, have been investigated with regard to their electrical properties. These compounds form a new class of solid-state lithium ion conductors with a different crystal structure compared with all those known so far. The materials are prepared by solid-state reaction and characterized by powder XRD and ac impedance to determine their lithium ionic conductivity. Both the niobium and tantalum members exhibit the same order of magnitude of bulk conductivity (ϳ10 ؊6 S/cm at 25°C). The activation energies for ionic conductivity (<300°C) are 0.43 and 0.56 eV for Li 5 La 3 Nb 2 O 12 and Li 5 La 3 Ta 2 O 12 , respectively, which are comparable to those of other solid lithium conductors, such as Lisicon, Li 14 ZnGe 4 O 16. Among the investigated materials, the tantalum compound Li 5 La 3 Ta 2 O 12 is stable against reaction with molten lithium. Further tailoring of the compositions by appropriate chemical substitutions and improved synthesizing methods, especially with regard to minimizing grain-boundary resistance, are important issues in view of the potential use of the new class of compounds as electrolytes in practical lithium ion batteries.
Optimization of Li-ion Conductivity of Garnet-type Li 5La3Nb2O12 by Nb-site Substitution Approach
2015
Solid state Li ion electrolytes based on the garnet type crystal structure have been successfully synthesized using the ceramic method. The approach employed in this thesis was doping of the Nb-site in Li5La3Nb2O12 with Sm and Gd and Li stuffing into the garnet-like oxides for charge balance. The resulting family of compounds have a nominal formula Li5+2xLa3Nb2-xSmxO12 (0 ≤ x ≤ 0.7) and Li5+2xLa3Nb2-xGdxO12 (0 ≤ x ≤ 0.45). Experimental techniques used for the characterization of the solid state materials include powder X-ray diffraction (PXRD) to determine the crystal structure, scanning electron microscopy (SEM) to analyze the microstructure, energy dispersive spectroscopy (EDS) to confirm the elemental composition, AC impedance spectroscopy to determine the lithium ion conductivity Fourier transform infrared spectroscopy (FTIR) to confirm the presence of OHand CO3 2groups in the samples and thermogravimetric analysis (TGA) to test the thermal stability of the compound. The most promising samples were the x = 0.3 member of the Sm-doped family and the x = 0.45 member of the Gd-doped family. Li5.6La3Nb1.7Sm0.3O12 showed a conductivity of 5.84 x 10-5 S cm-1 at room temperature, with an activation energy of 0.38 eV in the 25-225 °C. temperature range Li5+2xLa3Nb2-xGdxO12 showed the highest conductivity of 1.91 x 10-5 S cm-1 at room temperature with an activation energy of 0.38 eV in the temperature range 25-225 °C. Both show an order of magnitude higher conductivity than the parent compound, Li5La3Nb2O12.
Journal of the Korean Ceramic Society, 2016
In this study, we investigate the effect of the Li 3 BO 3 additive on the densification and ionic conductivity of garnet-type Li 7-La 3 Zr 2 O 12 solid electrolytes for all-solid-state lithium batteries. We analyze their densification behavior with the addition of Li 3-BO 3 in the range of 2-10 wt.% by dilatometer measurements and isothermal sintering. Dilatometry analysis reveals that the sintering of Li 7 La 3 Zr 2 O 12-Li 3 BO 3 composites is characterized by two stages, resulting in two peaks, which show a significant dependence on the Li 3 BO 3 additive content, in the shrinkage rate curves. Sintered density and total ion conductivity of the system increases with increasing Li 3 BO 3 content. After sintering at 1100 o C for 8 h, the Li 7 La 3 Zr 2 O 12-8 wt.% Li 3 BO 3 composite shows a total ionic conductivity of 1.61 × 10 −5 Scm −1 , while that of the pure Li 7 La 3 Zr 2 O 12 is only 5.98 × 10 −6 Scm −1 .
Enhanced Li+ Ionic Conduction and Relaxation Properties of Li5+2xLa3Ta2-xGaxO12 Garnets
Crystals
In the current work, we studied the effect of Ga+3 substitutions on the Ta+5 sites in Li5+2xLa3Ta2-xGaxO12 (LLT-Ga) lithium conducting garnets (with x = 0.1–0.5) in order to enhance the ionic conductivity of these materials. The current materials are prepared by solid state reaction and their electrical properties are studied by impedance spectroscopy measurements. XRD data showed that cubic garnet phases are obtained for LLT-Ga garnets. The ionic conductivity increased by one order of magnitude for x = 0.3 composition with a value of ~4 × 10−5 S/cm compared to that of Li5La3Ta2O12 material. Moreover, the hopping frequency and the concentration of mobile Li+ ions were estimated from analysis of the conductivity spectra, and it was found that both the concentration and mobility of Li+ ions increased with increasing Ga+3 content in the materials. The dielectric and relaxation properties were studied in the dielectric permittivity and electric modulus formalisms. The current materials ...
Solid State Ionics, 2008
In this paper the synthesis and conductivities of the garnet-related Li ion conductors, Li 5 Ln 3 Sb 2 O 12 (Ln=La, Pr, Nd, Sm, Eu), are reported. These phases show high Li ion conductivity, similar to previously reported for the related Li 5 La 3 M 2 O 12 (M=Nb, Ta) materials. Neutron diffraction structural studies are also reported for Li 5 La 3 Sb 2 O 12
Solid State Ionics, 2015
With the aim to improve the ionic conductivity of perovskite materials used for all-solid-state batteries, La (2/3) − x Li 3x TiO 3 with x = 0.11 (LLTO11) ceramics was prepared by a double mechanical alloying method. The influence of thermal treatments (furnace-cooling, SC and quenching, QC) on the crystalline structure and Li-ion conductive properties of the LLTO ceramics has been studied by X-ray powder diffraction (XRD), Raman scattering and impedance spectroscopy. XRD patterns of SC-samples exhibited a doubled perovskite with a tetragonal structure, whereas those of quenched samples indicated a simple cubic perovskite. The increase in the ionic conductivity of the LLTO11 ceramics was attributed to the disordered morphology that has promoted 3D-conductive mechanism. At room temperature, the grain and grain-boundary conductivities of the quenched LLTO11 ceramics reached values as large as 1.8 × 10 −3 S•cm −1 and 7.2 × 10 −5 S•cm −1 , respectively. All-solidstate batteries made from the LLTO11 solid-state electrolyte combining with LiMn 2 O 4 , and SnO 2 thin films as cathode and anode, respectively, possessed a charge-discharge efficiency of~61% and a charging capacity of 3.0 μAh/(cm 2 • μm) at a voltage of 1.6 V.
Structure and lithium ion conductivity of garnet-like Li5La3Sb2O12 and Li6SrLa2Sb2O12
Materials Research Bulletin, 2008
Oxides with the nominal chemical compositions Li 5 La 3 Sb 2 O 12 and Li 6 SrLa 2 Sb 2 O 12 were prepared by solid-state reaction. The structures were refined by the Rietveld method using powder X-ray diffraction data. The synthesis of Li 5 La 3 Sb 2 O 12 resulted in the well known garnet-related structure plus 5 wt.% of La 2 LiSbO 6 in the bulk. In contrast to that, Li 6 SrLa 2 Sb 2 O 12 could be synthesised in single garnet-related type phase. Lithium ion conductivities of Li 5 La 3 Sb 2 O 12 and Li 6 SrLa 2 Sb 2 O 12 were studied by the ac impedance method. The grain-boundary contribution to the total (bulk + grain-boundary) resistance is very small and about 5 and 3% for Li 5 La 3 Sb 2 O 12 and Li 6 SrLa 2 Sb 2 O 12 , respectively, at 24 8C and decreases further with increase in temperature. Among the investigated compounds, Li 5 La 3 Sb 2 O 12 exhibits the highest total (bulk + grain-boundary) and bulk ionic conductivity of 7.8 Â 10 À6 and 8.2 Â 10 À6 S cm À1 , respectively, at 24 8C. The structural data indicate that the coupled substitution Li + Sr ) La leads to a closure of the bottle neck like O-O distances of the shared edges of neighbouring Li octahedra and therefore reduces the mobility of Li ions in Li 6 SrLa 2 Sb 2 O 12 . Scanning electron microscope (SEM) images of the Li 6 SrLa 2 Sb 2 O 12 compound revealed well crystallised large homogeneous grains ($4.8 mm) and the grains were in good contact with the neighbouring grain, which leads to a smaller grain-boundary contribution to the total resistance. #