Effect of sintering conditions on the properties of sol-gel-derived Li<Subscript>1.3</Subscript>Al<Subscript>0.3</Subscript>Ti<Subscript>1.7</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>

Solid electrolyte Li_1.3Al_0.3Ti_1.7(PO₄)₃ was prepared by sol-gel method under different sintering conditions. The structural identification, surface morphology, electrochemical window, ionic conductivity, and activation energy of the Li_1.3Al_0.3Ti_1.7(PO₄)₃ sintered pellets were investigated by X-ray diffraction, scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. It is found that the sintering temperature and time have considerable effect on the properties of the Li_1.3Al_0.3Ti_1.7(PO₄)₃ sintered pellets. The Li_1.3Al_0.3Ti_1.7(PO₄)₃ pellet sintered at 900 °C for 2 h is denser than the pellets sintered at other conditions. Different sintering conditions result in the sintered pellet with different porosity. However, the sintering conditions have little effect on the electrochemical window of Li_1.3Al_0.3Ti_1.7(PO₄)₃. Among the Li_1.3Al_0.3Ti_1.7(PO₄)₃ pellets sintered at various conditions, the pellet sintered at 900 °C for 2 h shows the highest ionic conductivity of 3.46 × 10⁻⁴ S cm⁻¹ and the lowest activation energy of 0.2821 eV.     

Electrical properties of Li-based NASICON compounds doped with yttrium oxide

In the present study, the electrical properties of lithium-based Li_1.3Al_0.3???x Y _x Ti_1.7(PO₄)₃ (LAYTP) system is reported. Yttrium is a rare earth element and has been found to be an excellent sintering aid in ceramic electrode materials. Earlier attempts to replace the tetravalent Ti⁴⁺ using trivalent cations like Al³⁺, Y³⁺, In³⁺, and Sc³⁺ in rhombohedral NASICON structure have resulted in enhanced electrical conductivity. The effect of trivalent cation Y³⁺ doping in an optimized system Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) is discussed. The electrical properties of this ceramic compound in temperature range of 303 to 423 K and in the microwave frequency range of 20 MHz to 1 Hz were studied for the LAYTP system using impedance spectroscopy. The role of yttrium to improve the density of the material and thereby the study of the grain and grain boundary is explored.     

1,2-丙二醇辅助溶胶凝胶法制备NASICON型Li1.3Al0.3Ti1.7(PO4)3固体电解质

通过1,2-丙二醇辅助的溶胶凝胶方法制备了具有NASICON结构的固体锂离子导体Li_1.3Al_0.3Ti_1.7(PO₄)₃,并且通过热重/差热分析、X射线衍射分析、比表面观测、电化学阻抗谱以及计时电流法等对其各方面性能进行了表征. 通过使用1,2-丙二醇辅助方法,未额外添加络合剂,也未对pH值进行调整得到均匀的溶胶前驱体,并且通过在850～950oC不同高温段烧结得到无杂相的具有NASICON结构     

Influence of solid electrolyte particles size on ionic transport in model composite system (PVdF-HFP–Li1.3Al0.3Ti1.7(PO4)3)

The influence of filler particles size on lithium ion conductivity of composite polymer electrolytes was issued on model system vinylidenefluoride with hexafluoropropylene (PVdF-HFP)–Li_1.3Al_0.3Ti_1.7(PO₄)₃. Model electrolyte objects with filler grains of different sizes were prepared using a modified solvent casting method from a mixture of PVdF-HFP solution in dimethylformamide and Li_1.3Al_0.3Ti_1.7(PO₄)₃ solid electrolyte particles. The percolation threshold was defined and the transport properties of composite polymer electrolytes at different volume concentrations of the solid electrolyte investigated. A significant decrease in conductivity compared to that of ceramic solid electrolytes was observed. The size of the filler particles was found to affect the structure and transport properties of the prepared composite polymer electrolytes. The conductivity of the composite polymer electrolyte at 100 °C was found to increase by two orders of magnitude with the tenfold increase of the size of the filler particles.     

Vibrational spectroscopic study of lithium intercalation into LiTi2(PO4)3

Ex situ vibrational spectra are recorded during the first discharge of LiTi₂(PO₄)₃. Spectral changes are consistent with a two-phase model for the electrochemical insertion of Li⁺ ions. Differences in the frequencies and relative intensities of the LiTi₂(PO₄)₃ and Li₃Ti₂(PO₄)₃ bands are due to changes in the effective force constants, dipole moment derivatives, and polarizability derivatives as Li⁺ is inserted into LiTi₂(PO₄)₃. The intramolecular PO₄³⁻ bending modes (ν₂ and ν₄) are found to be more sensitive to Li⁺ insertion than the intramolecular PO₄³⁻ stretching modes (ν₁ and ν₃). This is because ν₂ and ν₄ are less localized than ν₁ or ν₃ and are more susceptible to small structural changes in the unit cell. Furthermore, a band at 487 cm^− 1 appears in the infrared spectrum of Li₃Ti₂(PO₄)₃. This band is assigned as a Li⁺ ion cage mode and is due to Li⁺ ions that occupy the M(3) and M′(3) sites in the Li₃Ti₂(PO₄)₃ structure. A small degree of band broadening is also detected in the vibrational spectra when Li⁺ ions are inserted, which might indicate some disordering in the cathode material.     

Y2O3·Cr2O3复合氧化物热力学性质的研究

在1182—1386K温度范围内,用固体电解质氧浓差电池:Mo|Cr,Y₂O₃,Y₂O₃·Cr₂O₃|ZrO₂(+MgO)|Cr,Cr₂O₃|Mo测定了复合氧化物Y₂O₃·Cr₂O₃的热力学性质。对于反应Y_{2关键词：}     

C-rate and temperature dependence of electrochemical performance of Li[Co0.1Ni0.15Li0.2Mn0.55]O2 cathode materials before and after Co3(PO4)2 coating

Li[Co_0.1Ni_0.15Li_0.2Mn_0.55]O₂ was synthesized, as a cathode material with high capacity, by a simple combustion method followed by annealing at 800?°C. Li[Co_0.1Ni_0.15Li_0.2Mn_0.55]O₂ cathode materials were coated with lithium-active Co₃(PO₄)₂ to improve the electrochemical performance of rechargeable lithium batteries. Morphologies and physical properties of Li[Co_0.1Ni_0.15Li_0.2Mn_0.55]O₂ before and after the Co₃(PO₄)₂ coating were analyzed with a scanning electron microscope equipped with an energy dispersive X-ray spectroscope. Transmission electron microscopy, powder X-ray diffraction, and Brunauer?CEmmett?CTeller surface area analyses were also carried out. The electrochemical performances of Li[Co_0.1Ni_0.15Li_0.2Mn_0.55]O₂ cathode material before and after Co₃(PO₄)₂ coating were evaluated by galvanostatic charge?Cdischarge testing at different charge and discharge densities. The temperature dependence of the cathode material before and after Co₃(PO₄)₂ coating was investigated at 0, 10, 20, 30, 40, and 50?°C at a rate of 0.1?C. Co₃(PO₄)₂-Li[Co_0.1Ni_0.15Li_0.2Mn_0.55]O₂ exhibited good electrochemical performance under high C-rate and experimental temperature conditions. The enhanced electrochemical performances were attributed to the formation of a lithium-active Co₃(PO₄)₂-coating layer on Li[Co_0.1Ni_0.15Li_0.2Mn_0.55]O₂.     

Structural and electrical properties of high-energy ball-milled NASICON type Li1.3Ti1.7Al0.3(PO4)2.9(VO4)0.1 ceramics

Nano-crystallites of Li_1.3Ti_1.7Al_0.3(PO₄)_2.9(VO₄)_0.1 NASICON type material are prepared by means of solid-state reaction of a stoichiometric mixture after milling it for 22 and 55 h. The milling reduces the average crystallite size of the ceramic to 80 and 60 nm, respectively. Mechanical milling changes structural parameters and the strain induced at the grain-boundaries plays a major role in improving electrical conductivity. An order of magnitude increase in electrical conductivity is observed in the material milled for 55 h compared to the unmilled material, which is also reflected in permittivity loss. Modulus and permittivity representations substantiate the constriction effect of grain-boundaries observed in the complex impedance representation.     

Mechanical behavior of Li-ion-conducting crystalline oxide-based solid electrolytes: a brief review

Li-ion-conducting solid electrolytes are receiving considerable attention for use in advanced batteries. These electrolytes would enable use of a Li metal anode, allowing for batteries with higher energy densities and enhanced safety compared to current Li-ion systems. One important aspect of these electrolytes that has been overlooked is their mechanical properties. Mechanical properties will play a large role in the processing, assembly, and operation of battery cells. Hence, this paper reviews the elastic, plastic, and fracture properties of crystalline oxide-based Li-ion solid electrolytes for three different crystal structures: Li_6.19Al_0.27La₃Zr₂O₁₂ (garnet) [LLZO], Li_0.33La_0.57TiO₃ (perovskite) [LLTO], and Li_1.3Al_0.3Ti_1.7(PO₄)₃ (NaSICON) [LATP]. The experimental Young’s modulus value for (1) LLTO is ~?200 GPa, (2) LLZO is ~?150 GPa, and (3) for LATP ~?115 GPa. The experimental values are in good agreement with density functional theory predictions. The fracture toughness value for all three of LLTO, LLZO, and LATP is approximately 1 MPa m^?2. This low value is expected since, they all exhibit at least some degree of covalent bonding, which limits dislocation mobility leading to brittle behavior.     

Influence of the size effect on the electrical conductivity of partially stabilized zirconia

The volume component of the electrical conductivity of bulk ceramics of the partially stabilized zirconia (ZrO₂)_0.94(Y₂O₃)_0.05(Al₂O₃)_0.01 is found to increase by a factor of 1.7 with the grain size decreasing from 600–800 to 200–300 nm. The observed effect is explained by the action of the pressure produced by surface tension forces, which shifts equilibrium toward the point of the polymorphic transition to the cubic phase.     

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.     

Effect of calcination conditions on lithium conductivity in Li<Subscript>1.3</Subscript>Ti<Subscript>1.7</Subscript>Al<Subscript>0.3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> prepared by sol-gel route

In order to study the influence of powder calcination temperature on lithium ion conductivity, synthesized Li_1.3Ti_1.7Al_0.3(PO₄)₃ (LATP) was calcined at temperatures between 750 and 900 °C. The shape and size of the particles were characterized employing scanning electron microscopy (SEM), and specific surface area of the obtained powder was measured. The crystallinity grade of different heat-treated powders was calculated from XRD spectra. Posteriorly, all powders were sintered at 1100 °C employing field-assisted sintering (SPS), and the electrical properties were correlated to the calcination conditions. The highest ionic conductivity was observed for samples made out of powders calcined at 900 °C.     

Influence of Al2O3 additions on crystallization mechanism and conductivity of Li2O-Ge2O-P2O5 glass-ceramics

The crystallization mechanism and conductivity of lithium aluminum germanium phosphate [LAGP] glass-ceramics fabricated from Li_1+xAl_xGe_2−x(PO₄)₃ (x=0.0-0.7) glass system were investigated as a function of Al₂O₃ additions. A non-isothermal analysis was performed to study the crystallization behavior of LAGP glass-ceramics at various heating rates (5-25K min⁻¹) by the Kissinger equation and the Augis-Bennett equation, illustrating volume crystallization for the glass-ceramics. The crystal identification and microstructure in glass-ceramics containing various Al₂O₃ contents were analyzed by means of XRD and FESEM. The main phase of the glass-ceramics was found to be LiGe₂(PO₄)₃, with AlPO₄ as the impurity phase. Additionally the highest total ionic conductivity (5.8×10⁻⁴ S/cm) at room temperature was obtained when x=0.5 for Li_1+xAl_xGe_2−x(PO₄)₃ (x=0.0-0.7) glass-ceramics, suggesting that it was a promising electrolyte for practical application in all-solid-state lithium batteries.     

ac ionic conductivity of hollandite type compounds from 100 Hz to 37.0 GHz

The frequency- and temperature-dependences of a.c. ionic conductivity of one-dimensional super-ionic conductors K-priderites with a hollandite type structures were investigated from 100 Hz to 37.0 GHz. Four kinds of K-priderite, K_1.6Mg_0.8Ti_7.2O₁₆, (K_1.3, Li_0.1) Mg_0.7Ti_7.3O₁₆, K_1.6Al_1.6Ti_6.4O₁₆ and (K_1.3, Li_0.2) Al_1.5Ti_6.5O₁₆, were studied. An equivalent circuit to combine the data of the complex conductivity at low and high frequencies was proposed. The data of complex conductivity at low frequencies can be analyzed in terms of the moving box model proposed by Beyeler et al. The transport of K⁺ ions at low frequencies is characterized by the cooperative motion of the K⁺ ions with various mobilities and is accompanied with the polarization of the K⁺ ions in the channels. The ion transport across intrinsic barriers at or above microwave frequencies is characterized by the frequency-independent ionic conductivity and is interpreted by the configurational model proposed by Beyeler et al. The height of intrinsic barriers is related to the lattice constants of a crystal.     

Potentiometric carbon dioxide sensor based on thin Li3PO4 electrolyte and Li2CO3 sensing electrode

Potentiometric CO₂ gas sensors with thin-film lithium phosphate (Li₃PO₄) electrolytes were developed by using radio frequency (RF) magnetron sputtering. Li₂CO₃ and a mixture of Li₂TiO₃ and TiO₂ were used as sensing and reference electrodes, respectively. By using the RF sputtering deposition process, we obtained a dense, crystalline, thin-film Li₃PO₄ electrolyte with good adhesion on the Al₂O₃ substrate. The thin-film Li₃PO₄ electrolyte had good ionic conductivity, i.e., 2.15?×?10^?6 S cm^?1 at 500 °C, and its activation energy was 0.97 eV. The thin-film Li₃PO₄ electrolyte was suitable for the miniaturization of potentiometric CO₂ sensors. The thin-film potentiometric CO₂ sensor provided relatively good sensing response for overall CO₂ concentrations (500 to 3,000 ppm and 5 to 20 %) at 500 °C. The Nernstian slope of 78.2 mV/decade obtained for CO₂ concentrations from 5 to 20 % at 500 °C was close to the theoretical value (76.6 mV/decade). Although the sensor’s reading deviated from the theoretical value at low CO₂ concentrations (500 to 3,000 ppm), the sensor provided better sensing performance than a potentiometric CO₂ sensor with a thick electrolyte. As a result, it was assumed that the thin-film sensor could be used to monitor the overall concentration of CO₂ in the environment.     

Grain size effects on dynamics of Li-ions in Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> glass-ceramic nanocomposites

Li₃V₂(PO₄)₃ glass-ceramic nanocomposites, based on 37.5Li₂O-25V₂O₅-37.5P₂O₅ mol% glass, were successfully prepared via heat treatment (HT) process. The structure and morphology were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD patterns exhibit the formation of Li₃V₂(PO₄)₃ NASICON type with monoclinic structure. The grain sizes were found to be in the range 32–56 nm. The effect of grain size on the dynamics of Li⁺ ions in these glass-ceramic nanocomposites has been studied in the frequency range of 20 Hz–1 MHz and in the temperature range of 333–373 K and analyzed by using both the conductivity and modulus formalisms. The frequency exponent obtained from the power law decreases with the increase of temperature, suggesting a weaker correlation among the Li⁺ ions. Scaling of the conductivity spectra has also been performed in order to obtain insight into the relaxation mechanisms. The imaginary modulus spectra are broader than the Debye peak-width, but are asymmetric and distorted toward the high frequency region of the maxima. The electric modulus data have been fitted to the non-exponential Kohlrausch–Williams–Watts (KWW) function and the value of the stretched exponent β is fairly low, suggesting a higher ionic conductivity in the glass and its glass-ceramic nanocomposites. The advantages of these glass-ceramic nanocomposites as cathode materials in Li-ion batteries are shortened diffusion paths for Li⁺ ions/electrons and higher surface area of contact between cathode and electrolyte.     

Green luminescence and EPR studies on Mn-activated yttrium aluminum garnet phosphor

Yttrium aluminum garnet (Y₃Al₅O₁₂) and Mn activated Y₃Al₅O₁₂ phosphors have been prepared by urea combustion route in less than 5 min. The phosphors are well characterized by powder X-ray diffraction, Scanning electron microscopy and Fourier-transform infrared spectroscopic techniques. Photoluminescence tests on the pure Y₃Al₅O₁₂ showed a strong green emission at 525 nm (2.36 eV) attributed to the strongly allowed transition of F⁺ center whereas in Mn²⁺ activated YAG the green emission at 519 nm is due to the ⁴T₁ (G)→⁶A₁ (S) transition of Mn²⁺ ions. EPR studies have been carried out on Mn²⁺ activated Y₃Al₅O₁₂ phosphor at 300 and 110 K. From EPR spectra the spin-Hamiltonian parameters have been evaluated. The magnitude of the hyperfine splitting (A) indicates that the Mn²⁺ ions are in a moderately ionic environment. The spin concentration (N) and paramagnetic susceptibility (χ) have been evaluated and discussed.     

Preparation and characteristics of Li4Ti5O12 with various dopants as anode electrode for hybrid supercapacitor

Spinel-Li₄Ti₅O₁₂ is successfully synthesized by a solid phase synthesis. The Li₄Ti₅O₁₂ powders with various dopants (Al³⁺, Cr³⁺, Mg²⁺) synthesized at 800 °C are in accordance with the Li₄Ti₅O₁₂ cubic spinel phase structure. The dopants are inserted into the lattice structure of Li₄Ti₅O₁₂ without causing any changes in structural characteristics. In order to study the effect on various dopants, the hybrid supercapacitor is prepared by using un-doped Li₄Ti₅O₁₂ and doped Li₄Ti₅O₁₂ in this work. The electrochemical performance of the hybrid supercapacitor is characterized by impedance spectroscopy and cycle performance. The results show Cr³⁺ and Mg²⁺ dopants enhance the conductivity of Li₄Ti₅O₁₂. Also, Al³⁺ substitution improves the reversible capacity and cycling stability of Li₄Ti₅O₁₂. It is found that effect of dopant on the electrochemical performance of Li₄Ti₅O₁₂ as electrode material for hybrid supercapacitor where the EDLC and the Li ion secondary battery coexist in one cell system.     

Preparation of binder-free thin film Li4Ti5O12 anode with an adjustable thickness through anodic TiO2 nanotubes

Binder-free thickness-controllable Li₄Ti₅O₁₂ for application in lithium ion batteries was fabricated by the reaction of Li₂CO₃ and anodic nanotubular TiO₂ at 800 °C. As the concentration of Li₂CO₃ increased, the thickness of Li₄Ti₅O₁₂ film increased, leading to increase in discharge capacity. The Li₄Ti₅O₁₂ film prepared at the optimized concentration of Li₂CO₃ of 3.8 × 10^?6 mol displayed the maximum capacity of 104 μA h cm^?2 at the first cycle, which corresponds to 103 mA h g^?1. We found that excess Li₂CO₃ led to creation of LiTiO₂ phases in the Li₄Ti₅O₁₂ film, which reduced the discharge capacity. For comparison, a Li₄Ti₅O₁₂ film was prepared by the reaction of Li₂CO₃ on a non-anodized Ti foil. In this case, discharge capacity was dramatically reduced due to the formation of Li₂TiO₃ phases in Li₄Ti₅O₁₂, which was confirmed by TEM and XRD analysis.     

The all-solid-state battery with vanadate glass-ceramic cathode

The Ga-Ag-Li|Li₇La₃Zr_1.89Al_0.15O₁₂|(Li₂O–B₂O₃–V₂O₅ + Fe) all-solid-state electrochemical cell has been designed with a simple sintering process. The Li₇La₃Zr_1.89Al_0.15O₁₂ solid electrolyte was prepared by sol-gel method. The lithium borovanadate glass was obtained by a convenient melt quenching technique. Cycliс voltammetry has shown that the current densities of the cell at 300 °C can reach several hundreds of μA cm^?2. At this temperature, the single cell voltage is about 3.2 and 0.8 V in the charged and discharged state, correspondingly. This cell produces a current enough to make a single LED of white color working. The cell surface discharge capacity exceeds 230 μAh cm^?2.