Solid State Ionics最新文献

The oxygen isotope exchange method was used to investigate the kinetics of the interaction between gaseous oxygen and LaGaO₃-based oxides in a temperature range of 650 to 850 °C, with an oxygen pressure of 10 mbar. The stable isotopes of ¹⁸O/¹⁶O were used as labelled ions. The temperature dependencies of the heterogeneous oxygen exchange rate (r_H), the oxygen dissociative adsorption rate (r_a), the oxygen incorporation rate (r_i), and the oxygen diffusion coefficient (D) were determined. A comparative analysis of the r_H and D values for La_0.8Sr_0.2Ga_0.8Mg_0.2O_3–δ was carried out with a view to identifying any similarities or differences when compared with the literature data on oxides with similar compositions. The effect of ${\mathrm{Fe}}_{\mathrm{Ga}}^{\prime }$ doping and the creation of an A-sublattice deficiency on the kinetic characteristics were investigated using the (La_0.8Sr_0.2)_0.98Ga_0.7Fe_0.1Mg_0.2O_3–δ oxide as a case example. Correlations between the rate-determining step of oxygen exchange and the modification of the oxide composition were identified.

The LiNi_0.33Mn_0.33Co_0.33O₂ compound is a cathode material for Li-ion batteries. Li diffusion in this material directly influences charging/discharging times, power densities, maximum capacities, stress formation and possible side reactions. In the present study, Li tracer self-diffusion is investigated on ion-beam sputtered films after deposition (amorphous) and after crystallization at 700 °C. For the experiments, ⁷Li isotope enriched films with about 1.5 μm thickness were combined with a 50–90 nm thick ⁶Li tracer layer with the same chemical composition. Afterwards, the films were diffusion annealed between 100 and 300 °C. For analysis secondary ion mass spectrometry in depth profile mode was applied. The diffusivities of the crystalline films are identical to those of sintered bulk samples within error limits as known from literature and show an activation enthalpy of diffusion about 0.9 eV. In contrast, the diffusivities of the amorphous films are about one order of magnitude lower at 100 °C due to a higher activation enthalpy of diffusion of 1.1 eV. We attribute this higher activation enthalpy to a hindered diffusion in the amorphous state of the two-dimensional ion conductor.

Due to their high ionic conductivities, sulfide-based solid electrolytes (SEs)—such as argyrodite Li₆PS₅Cl—are good candidates for all-solid-state lithium-ion batteries (ASSLIBs). For adequate energy density, the thinner SE layers of ASSLIBs, the better, but it must also be durable to avoid short circuits. Using SiO₂ fibers in the SE layer as a support, we used a liquid process to produce all-inorganic, self-standing-sheet argyrodite-SEs with a thickness of approximately 60 μm, without resorting to organofluorine compounds such as polytetrafluoroethylene (PTFE) or polyvinylidene difluoride (PVDF). The ionic conductivity of a sheet containing 20 % SiO₂ fibers was 4.2 × 10⁻⁴ S cm⁻¹ at 25 °C. We also prepared graphite composites as anodes using argyrodite SE containing SiO₂ fibers. In addition, we fabricated ASSLIB cells using these SE sheets, Ni_1/3Mn_1/3Co_1/3O₂-composite positive, and graphite-composite negative electrodes and evaluated their charge–discharge characteristics.

New optical materials, in particular mixed lithium niobate-tantalate (LNT) solid solutions, are promising for application in photonics and microelectronics. Proton exchange is one of the widely used methods for producing low-contrast optical waveguides. The structure and properties of the proton exchange layers in X- and Z-cut samples were systematically studied using various structural and integrated optical methods. Direct proton exchange leads to the formation of a waveguide layer with a step-like refractive index profile. The waveguide-substrate boundary is clear (not blurred). At this boundary, the parameters of the crystal lattice change abruptly. Proton exchange leads to with the formation of deformation twins and surface damage of the LNT crystal structure. Indices and geometric parameters of surface damage were determined. The results of phase analysis of the samples indicate the presence of β-phases with high degrees of deformation of the crystal lattice. The calculated kinetic parameters of proton diffusion in LNT are significantly lower than for lithium niobate crystals, which is due to both the tantalum impurity and the greater disorder of the crystal lattice, and this leads to a decrease in the increment of the refractive index. The results provide a physical basis of diffuse process and design and fabrication of proton exchange waveguides in mixed LNT solid solutions.

In this paper, ring-shaped Fe₂O₃ anode materials were modified by using ion doping. Ring-shaped Fe₂O₃ anode materials doped with different concentrations of Cu were prepared by hydrothermal method. The overall morphology of ring-shaped Fe₂O₃ did not change after Cu doped while the lattice deformation led to the generation of more oxygen vacancies and thus enhanced the lithium storage capacity. The Cu doped ring-shaped Fe₂O₃ showed excellent cycling and multiplicity performance, and the Fe₂O₃ material with 3 % Cu doped had the best electrochemical performance, with a specific capacity of 862.6 mAh g⁻¹ after 100 cycles at a current density of 0.1C and a better multiplicity performance. The experimental results indicated that the electrochemical performance of Fe₂O₃ anode materials can be effectively improved by ion doping.

Bilayer electrolytes can enhance the performance of protonic ceramic fuel cells (PCFCs). In this work, the transport of charged defects through ${\text{BaZr}}_{0.8}{Y}_{0.2}{O}_{3-\delta }$|${\text{BaZr}}_{0.1}{\mathrm{Ce}}_{0.7}{Y}_{0.1}{\mathrm{Yb}}_{0.1}{O}_{3-\delta }$ bilayer electrolytes is modeled using a Nernst–Planck–Poisson formulation. New parameter sets were fitted to accurately represent the conductivity data and predict the i – V curve. The concentration and electrostatic potential profiles were calculated, along with the defect fluxes. The results show that the bilayer electrolyte exhibits lower hole conduction compared to the corresponding single-layer electrolytes. Additionally, a positive proton concentration gradient towards the cathode side is observed in the bilayer electrolyte, which is not present in single-layer electrolytes. The slope of the concentration profile increases as the $L_{\mathrm{BZY}}/L_{\mathrm{tot}}$ ratio decreases, corresponding with improved cell performance. This observed increase in proton concentration towards the cathode side suggests favorable conditions for proton supply to the cathode, thereby enhancing overall cell performance.

In this paper, carbon-coated Mn₃O₄ nanoparticles were synthesized by sintering the gel containing manganese acetate, PAN and DMF. Being heated to 500 °C in air at a heat rate of 13 °C/min, and then taken out immediately from the furnace, the gel converted to carbon-coated Mn₃O₄ nanoparticles with 20–30 nm sized Mn₃O₄ nanoparticles encapsulated in PAN-derived carbon. Unlike electrospinning and subsequent sintering the electrospun precursor in an inert atmosphere to synthesize metal oxide/carbon composite fibers, carbon-coated Mn₃O₄ nanoparticles with the low carbon content of 8.9 % were produced by sintering the gel precursor in air. As a cathode material for ZIBs, carbon-coated-Mn₃O₄ nanoparticles exhibit a high capacity of 557 mAh g⁻¹ at a current density of 0.1 A g⁻¹ after 300 cycles and good capacity retention performance during cycling. Its high capacity and good capacity retention performance are attributed to its low carbon content and porous PAN-derived carbon coating. Its low carbon content minimizes the negative impact of PAN-derived carbon on its capacity; its porous PAN-derived carbon coating prevents the cracking of Mn₃O₄ nanoparticles during charging-discharging and improves the electronic conductivity of Mn₃O₄ nanoparticles. The simple conducted technology synthesizes the carbon-coated Mn₃O₄ nanoparticles with a high capacity and good capacity retention performance, which makes it a promising route in the commercial production of cathode materials for ZIBs.

The REBa₂Fe₃O_8+δ (RE = Nd, Sm, Pr) perovskites are investigated as potential cobalt-free electrodes in symmetrical solid oxide fuel cells (SOFCs). After the preparation of samples by a soft chemistry route, we first characterized the intrinsic properties and then determined the electrochemical performance after the deposition of porous electrodes to obtain symmetrical cells. Analytical techniques such as X-ray diffraction (XRD) at room and high temperatures, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), dilatometry (TEC), and 4-probe conductivity measurements were employed to characterize exhaustively structural, thermal and electrical properties of the samples. The electrochemical characterization was further investigated through electrochemical impedance spectroscopy (EIS) as well as fuel cell testing conducted on electrolyte-supported symmetrical cells. XRD showed that all samples have a cubic structure with the $\mathrm{Pm}\overline{3}m$ space group. However, during TEM experiments, it was observed that SmBa₂Fe₃O_8+δ presents a quintuple nano-ordering perovskite structure. Pr-based sample shows the highest electrical conductivity (68 S cm⁻¹ at 500 °C), while NdBa₂Fe₃O_8+δ presents the lowest area specific resistance in air (0.47 Ω cm² at 600 °C) revealing that the disordered perovskite structure is more efficient than the quintuple nano-ordered phase of SmBa₂Fe₃O_8+δ in the oxygen reduction reaction (ORR). The use of NdBa₂Fe₃O_8+δ as electrodes in symmetrical cells has been demonstrated between 500 °C and 600 °C.

Interface construction must provide electrochemical compatibility between solid electrolyte (oxide) and cathode/anode materials for all-solid-state batteries (ASSBs). Layered rock-salt oxides (cathode) have good compatibility with LISICON compound Li_3.5Ge_0.5V_0.5O₄. The crystal structures of layered rock-salt cathode and LISICON solid electrolyte solid remain almost unchanged even after co-firing at 973 K. Furthermore, mixtures after co-firing exhibited electrochemical activity closely resembling that of pristine cathodes. Based on these findings from experimentation, a green sheet process was conceived with cathode/electrolyte stacking layers prepared by tape casting, stacking, and co-sintering. The obtained laminated cathode/electrolyte composites were evaluated with a half-cell configuration using polymer electrolyte on the Li anode side at 333 K and 0.01C current density, revealing charge-discharge profiles closely resembling those of cathodes in an ordinary liquid electrolyte battery. The areal capacity increased almost in direct proportion to cathode particle loading, reaching approximately ∼1.2 mAhcm⁻². The Li ionic conductivity of the LISICON electrolyte is less than approximately 10⁻⁴ Scm, indicating that the solid electrolyte particles with LLZO garnet core and LISICON shell can be specially designed as a solid electrolyte with higher ionic conductivity. Using them as the electrolyte in laminated composites, we conducted brief charge-discharge experiments.

In protonic ceramic fuel cells using Ba(Zr,M)O_3-δ (M: trivalent dopant elements) as the electrolyte, the precipitation of BaM₂NiO₅ due to Ni diffusion from the co-sintered NiO-based electrode causes degradation of protonic ceramic fuel cells. However, BaM₂NiO₅ itself has been little studied, and even possible stable crystal structures and compositions have not been fully characterized. In this study, we investigated the dynamic and energetic stability of BaM₂NiO₅ for various trivalent M elements by using first-principles calculations. First, dynamically stable crystal structures were determined for all compositions from phonon dispersion analysis. The formation energies showed negative values in the case of M = lanthanide elements, B, Ga, Tl and Y. The contribution of vibrational entropy to the formation energy of BaM₂NiO₅ was insignificant, and the internal energy was dominant. The chemical bonding analysis revealed that in BaM₂NiO₅, the covalent nature of the M-O bond and the ionic nature of the BaO bond are dominant in the stability of the crystal structure. Precipitation of BaM₂NiO₅ in Ba(Zr,M)O_3-δ was suggested to be dominated by a specific threshold value of formation energy. The validity of that assumption was discussed in terms of the relationship between the factors involved in precipitation and the ionic radius of M element. The formation energy of BaM₂NiO₅ in M = lanthanide elements and Y showed a downward convex tendency with M = Pm as the minimum value. The reason for this was discussed in terms of the characteristics of the crystal structure of BaM₂NiO₅, suggesting that the tensile strain in the M-O bonds and the compressive strain in the NiO and BaO bonds relax with the ionic radius of the M element.