Solid State Ionics最新文献

Liquid ammonia is an attractive candidate for use as a hydrogen carrier because of its high volumetric density. The successful development of direct ammonia proton-conducting ceramic fuel cells (PCFCs) operating at intermediate temperatures can be seamlessly integrated into the current infrastructure without the need for investing in hydrogen gas pipelines and storage facilities. However, the low power output of PCFCs using ammonia fuel hinders their practical applications. In this study, we systematically investigated the ammonia conversion ratio and rate, maximum power density, open-circuit voltage, and ohmic and polarization resistances of PCFCs (Ni-BaCe_0.7Zr_0.1Y_0.1Yb_0.1O_3−δ |BaCe_0.7Zr_0.1Y_0.1Yb_0.1O_3−δ| PrBaCo₂O_5+δ) for ammonia and hydrogen fuels at intermediate temperatures of 500–650 °C and quantitatively assessed the impact of Ru catalyst loading on the electrochemical performance of direct ammonia PCFC. Ru loading improved the maximum power density of the direct ammonia PCFC from 100 to 149 mWcm⁻² at 500 °C. Combined analysis of gas chromatography and AC impedance spectroscopy revealed that Ru catalysts improved the internal ammonia reforming rate by a factor of 1.9 at 500 °C and reduced polarization resistance by a factor of 1.4 at 500 °C. All results consistently support that the enhanced maximum power density of the direct ammonia PCFC is predominantly attributed to the improved electrochemical reaction kinetics at the electrode/electrolyte/gas interface.

BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ is a widely studied proton conductor for solid oxide fuel cells but its structure has not been examined in detail. In this study, we synthesized a pure, well-crystallized BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ powder via a glycine-nitrate process. Using Rietveld analysis on X-ray and neutron diffraction powder patterns collected both at room temperature and at elevated temperatures, we investigate the crystal structure of BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ. At room temperature, the sample exhibits I4/mcm tetragonal symmetry, with cell parameters of a = 6.14911(7) Å and c = 8.87903(14) Å. The structure of BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ can be described by a distortion of the ideal cubic perovskite (a_p), resulting from the cooperative tilt of the (Zr,Ce,Y,Yb)O₆ octahedra along the [001]_p axis (tilt system a⁰a⁰c⁻). Within the octahedra, it consists of a disordered arrangement of Zr, Ce, Y, and Yb atoms with an average distance (Zr,Ce,Y,Yb)-O of 2.219 Å. At around 650 °C, BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ undergoes a phase transition to the primitive cubic structure Pm$\overline{3}$m. This transition is characterized by a progressive decrease in the tilt angle, indicating a continuous phase transition, and is tricritical in nature.

Crystallographic data for BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ obtained from neutron data have been deposited at the Cambridge Crystallographic Data Centre, CSD 2341244 (room temperature) and CSD 2341246–2341252 (100 to 700 °C).

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.