Solid State Ionics最新文献

Prussian blue analogues (PBAs), due to their high theoretical capacity, low cost, and ease of preparation, are among the most promising cathode materials for sodium-ion batteries. However, most syntheses are conducted in aqueous solutions using co-precipitation methods, and the large lattice gaps in PBAs make it challenging to effectively control interstitial water content. Interstitial water within the structure of PBAs has been a primary cause of structural instability, performance degradation, and a major barrier to their widespread application. Herein, the incorporation of large-radius ions (K⁺, Ba²⁺, Ca²⁺, La³⁺) into the structure of iron-based Prussian Blue via ball milling and its impact on the structure and properties of the material are investigated. The ions (Ba²⁺, Ca²⁺, La³⁺) readily react with (C₂O₄)²⁻ during the synthesis process to form oxalate impurities. Nevertheless, through the solvent-free ball milling method, K⁺ ions were successfully incorporated into the bulk structure of the material, resulting in the synthesis of Na_0.32K_1.53Fe[Fe(CN)₆]_0.98•□_0.02•0.82H₂O (NaK-PB) with minimal water content. Benefiting from the enhanced structural stability of the material, NaK-PB retained a reversible capacity of 91.4 mAh g⁻¹ in 500 cycles at 0.1C, with a capacity retention rate 64% higher than that of material without K⁺ doping. This work presents a new strategy for reducing interstitial water content in PBAs and aids in advancing the commercial application of solvent-free ball milling synthesis for PBAs.

One big risk for commercial solid oxide fuel cells (SOFCs) is the potential delamination between cathode and electrolyte layers. It can be effectively alleviated by the thermal expansion offset strategy proposed in 2021, i.e., conventional cathode composited with the negative thermal expansion oxides. Here novel composite cathodes designated as La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF)-xSm_0.85Zn_0.15MnO₃ (SZM) (x = 0, 5, 10, 15, and 20 wt.%) are developed. Random phase boundaries with apparent lattice distortion are formed between LSCF and SZM phases. The best electrochemical performance is obtained for x = 10%. The corresponding peak power density at 923–723 K is 1.151–0.147 W·cm⁻², which is 57–69% higher than that (0.731–0.087 W·cm⁻²) for x = 0. More importantly, markedly enhanced long-term and thermal cycling stability is also obtained. Results of electrical conductivity, electrochemical impedance spectroscopy (EIS) and distribution of relaxation time (DRT) results further confirm that improved thermal match between cathode and electrolyte layers should be responsible for the high performance of intermediate temperature SOFCs (IT-SOFCs).

In this study, La_1-xBa_xMnO₃ (x = 0.03, 0.27, 0.5) solid solutions were synthesized, and their structure and defect incorporation processes were investigated. The investigations were conducted using XRD, Positron Annihilation Lifetime, and Doppler Broadening Spectroscopy methods. Depending on the La/Ba ratio, the mechanism of defect incorporation in these compounds was studied, and vacancies of La and Ba atoms in the structure were determined. Three lifetime components are observed in PALS investigations. An increase in x results in a decrease in all three lifetime components. The results indicate that an increase in x leads to the formation of 0D (anion and cation point vacancies) and 3D (lattice distortions and interplanar distances) defects in the structure. Doppler Broadening results reveal a decrease in open volume defects and the presence of cationic defects.

In the wavenumber range 1000–2000 cm⁻¹, weak second-order spectra have been discovered for the first time in the Raman spectra of the ferroelectric phase of ceramic solid solutions Li_0.12Na_0.88Ta_yNb_1-yO₃ (y = 0–0.5). They correspond to bound states of fundamental polar vibrations of oxygen ions of O₆ oxygen octahedra of A₁- and E-type symmetry and arise only due to strong anharmonicity of vibrations. It has been shown that the effects of strong anharmonicity manifest themselves most clearly for librational vibrations of O₆ oxygen octahedra as a whole. The Raman band (ν = 76 cm⁻¹, T = 293 K) corresponds to the librational vibrations of O₆ oxygen octahedra. Solid solution of the composition Li_0.12Na_0.88Ta_0.5Nb_0.5O₃ is characterized by the most disordered sublattice of niobium and tantalum. The band of this ceramics composition with increasing temperature experiences a strong broadening and a decrease in intensity, compared to other bands of the spectrum; at temperatures above 650 K the band is completely blurred into the wing of the Rayleigh band. Note that all this happens in the pre-transition region of the diffuse superionic phase transition in the range ≈670-730 K. This fact indicates the dynamic disordering of the sublattice of O₆ oxygen octahedra. Dynamic disordering accompanies the phase transition to the superionic state in the Li_0.12Na_0.88Ta_0.5Nb_0.5O₃ solid solution; therefore, the activation energy of ionic conductivity decreases sharply. In this case, the disorder of cations in the sublattice of niobium and tantalum is the greatest precisely at y = 0.5. It facilitates the superionic phase transition. Dynamic disordering of the O₆ oxygen octahedra sublattice as a whole was not detected for other compositions of Li_0.12Na_0.88Ta_yNb_1-yO₃ solid solutions with y < 0.5 in the studied temperature range. A phase transition is observed (through some intermediate metastable state) to a state with high ionic conductivity for lithium at a relatively high value of activation energy for conductivity before and after the transition for these compositions. Thus, approaches have been developed to predict the possibility of superionic conductivity in perovskite oxygen-polyhedral structures with the general formula Li_0.12Na_0.88Ta_yNb_1-yO₃ based on studying the concentration and temperature dependences of first- and second-order Raman spectra. The developed approaches are apparently valid for a wider range of oxygen-polyhedral structures.

All-solid-state lithium batteries are in great demand, but the problem of high interfacial resistance between the cathode and solid electrolyte needs to be addressed. The effect of heat treatment of the cathode half-cells on the LiFePO₄ | Li₇La₃Zr₂O₁₂ interfacial resistance was studied. According to differential scanning calorimetry, the interaction between the cathode material and Li₇La₃Zr₂O₁₂ begins at 699 °C. It was also shown via X-ray diffraction data that increasing the annealing temperature from 600 to 700 °C leads to the appearance of impurities related to the interaction of the solid electrolyte with LiFePO₄ (La₂Zr₂O₇ and LaFeO₃). A scanning electron microscopy study demonstrated that LiFePO₄ has good contact with ceramic electrolyte without and after heat treatment. The lowest resistance at the LiFePO₄ | Li₇La₃Zr₂O₁₂ interface (∼2000 and 30 Ohm cm² at 100 and 300 °C, respectively) was obtained for half-cells without heat treatment. Thus, heat treatment leads to an increase in the interfacial resistance caused by the interaction of LiFePO₄ with Li₇La₃Zr₂O₁₂

A series of solid polymer electrolyte films were prepared using a casting solution with a polymer matrix comprising 49% poly(methyl methacrylate)-grafted natural rubber (MG49). These films incorporated binary lithium salts: lithium tetrafluoroborate (LiBF₄) combined with either lithium trifluoromethanesulfonate (LiTf) or lithium iodide (LiI). These films' dielectric properties and ion association behavior were examined using potentiostatic electrochemical impedance spectroscopy (EIS) and Fourier transform infrared (FTIR) deconvolution. The key findings demonstrated that the increase in both the dielectric constant (ɛ_r) and dielectric loss (ɛ_i) was significantly correlated with enhanced ionic conductivity, reaching a value of 1.89 × 10⁻⁶ S cm⁻¹, which was attributed to enhanced ionic and segmental mobility. A peak observed in the M_i versus frequency plot confirmed the ionic conductor behavior. The (30:70) ratio of LiBF₄ to LiI exhibited the highest performance, with superior ionic conductivity, dielectric behavior, tangent loss, number of charge carriers, mobility, and diffusion coefficient, surpassing the performance of the single salt or LiBF₄ to LiTf. This indicates that the combination of LiBF₄ and LiI is particularly effective for applications requiring improved dielectric properties.

In the industry of high-temperature sensors and actuators, materials capable of delivering high ferroelectric, dielectric, and specifically stable/high piezoelectric performances above 1000 °C are in demand. Hence, perovskite-like layered structured (PLS) have gained popularity due to their high Curie temperature (T_C) and ferroelectric properties, but the low piezoelectric coefficient (d₃₃) at high temperature (>1000 °C) is the problem statement to be explored and improved. Herein this research, La_1.97(LiCe)_0.03Ti₂O₇:xwt%MnO₂ (LLCTO:xMn) with x = 0–0.3 ceramic series has been explored to study the ultra-high structural, ferroelectric, electric, dielectric, and piezoelectric properties. Among all compositions, LLCTO:0.2Mn ceramic has demonstrated ultra-high performances with remnant polarization (P_r) of ∼1.84 μC/cm², piezoelectric co-efficient (d₃₃) of 9 pC/N, resistivity of ∼10¹¹ Ω.cm, relative dielectric constant (ɛ_r) of 46, and minor dielectric loss (tanδ) of 0.17 which are much improved compared to pure La₂Ti₂O₇ (LTO) and pristine La_1.97(LiCe)_0.03Ti₂O₇ (LLCTO) ceramics. The LLCTO:0.2Mn ceramic has exhibited the high T_C of 1415 °C. Moreover, thermally stable multifunctional performances are measured where LLCTO:0.2Mn ceramic has demonstrated a high d₃₃ of ∼8.5 pC/N at 1200 °C and resistivity of ∼2.4 × 10⁷ Ω.cm even at 1000 °C, which are much better than the earlier reports. From the analysis, LLCTO:0.2Mn ceramic has demonstrated the potential to be utilized in high-temperature (>1000 °C) piezoelectric devices.

N-doped hierarchical porous carbon sheet was prepared through calcination of a sodium alginate film precursors containing Zn-2-methylimidazole coordination complex. The film precursors could be obtained at room temperature. The introduction of coordination complex cannot cause the change of sheet morphology, but it can promote the generation of large pore structure. Due to the hierarchical porous structure and N doping, the carbon materials present excellent electrochemical behaviors when used as supercapacitor electrode materials. It exhibited a high specific capacitance of 210.4 F g⁻¹ at 2 A g⁻¹ in a two-electrode system with a capacitance retention of 83.4% over 10,000 cycles.

Electrochromic materials have been widely applied in smart windows due to their color conversion and adjusting indoor solar radiation abilities. The researches on electrochromic properties of tungsten bronzes with near-infrared light absorbing abilities are important to obtain multifunctional smart windows. Here, nano potassium tungsten bronze K_xWO₃ with space group P6₃/mcm has been synthesized to study the effects of crystal structures and valence states of W ions on its electrochromic properties. By altering the composition of reaction solution in solvothermal method, the K content x of samples can be controlled together with the adjustments in sizes of hexagonal and trigonal channels in the crystal structure and valence states of W ions. The maximum optical modulation and coloration efficiency are achieved for the maximum x. The enhanced electrochromic performance mainly benefits from the synergistic size effects of hexagonal and trigonal channels.

Polyphosphate, as the cathode material of sodium ion battery(SIB) has the advantages of good structural stability and long service life, but suffer from poor conductivity and low specific capacity. The doping of heteroatom and coating of carbon are considered to be two effective measures to overcome its shortcomings. In this work, the Bismuth(Bi)-doped and carbon-coated materials Na₃V_2-xBi_x(PO₄)₂F₃/C with various Bi³⁺ doping levels(x = 0.03,0.05,0.07) were prepared by a facile sol-gel method combined high temperature calcination. The effect of Bi³⁺ doping on the electrochemical properties was systematically investigated. The Na₃V_1.95Bi_0.05(PO₄)₃F₃/C showed the best electrochemical performance with the specific capacities of 107.4, 94.3, 92.4, 86.2 mAh·g⁻¹ at 0.1 A·g⁻¹(0.78C), 0.2 A·g⁻¹(1.56C), 0.5 A·g⁻¹(3.9C), 1.0 A·g⁻¹(7.8C) respectively, and 90.4% of specific capacity was retained after 100 charge/discharge cycles, which has a greatly increase compared with the Na₃V₂(PO₄)₃F₃ material. This is attribute to the improving of the conductivity, the diffusion capacity and the structural stability of the material by Bi-doping and carbon coating.