Solid State Ionics最新文献

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.

Developing effective strategies to promote the sodium-ion storage performance of hard carbon anodes is essential for its practical application in sodium-ion batteries. The carbonization process plays a crucial role in regulating the microstructure of hard carbon. Conventional carbonization methods of slow-heating have hit a bottleneck in structural controls of hard carbon materials. Herein, hard carbon with high-rate and low-temperature sodium storage capability is ultrafast synthesized by flash Joule heating. Compared to the hard carbon synthesized by conventional slow-heating, the hard carbon synthesized by flash Joule heating has smaller particle size, larger interlayer spacing, and larger closed-pores leading to superior performance. This work provides a simple and effective method of boosting sodium-ion storage performance for hard carbon materials.

Poly(thiophene-3‑boronic acid) (PTBA) was studied as a promising active material for aqueous environments in this paper. Using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), the solubility and electrochemical behavior of it was studied in a range of aqueous solutions. Fourier Transform Infrared Spectrometry (FTIR) results verify the successful synthesis. PTBA shows promising solubility qualities in certain pH ranges, especially in alkaline solutions. However, among alkaline, neutral, and acidic environments the best environment for redox properties of aqueous 1 mM PTBA is the neutral one. The peak current (i_p) of 1 mM PTBA for 100 mV/s in the neutral environment is 0.01 mA and half peak potential (E_p/2) is −0.1 V (vs Ag/AgCl). Diffusion coefficient of PTBA is found as 4.97 × 10⁻⁸ cm²/s. The impedance tests also confirm that the neutral solvent decreases the charge transfer resistance.

The mesoporous electrode material offers a high surface area, excellent porous texture, and optimal pore-size distribution, facilitating increased active sites for ion accretion and enhanced ionic diffusion rates. NiMoO₄, TiS₂, and their composites such as NT-1, NT-2, NT-3, and NT-4 composites have been prepared by hydrothermal approach to enhance the capacitance of supercapacitor electrodes. Different methodologies have been employed to analyze the optical, morphological and structural characteristics of the synthesized materials. X-ray diffraction was utilized to assess the crystalline nature of both the pristine materials and composites. Scanning electron microscopy examination confirmed the formation of mesoporous and irregular nanoparticles with sizes ranging from 50 to 100 nm. Fourier-transform infrared spectroscopy was employed to examine the stretching vibrations of the prepared samples. Through photoluminescence (PL) analysis, the energy band gap of the NT-1 composite was decisive to be 2.78 eV. The NT-1 composite exhibits an impressive specific capacitance of 1257.14 Fg⁻¹ at 1 Ag⁻¹, attributed to its huge surface area, efficient charge transfer, and synergistic effect while demonstrating remarkable stability after 5000 cycles with 92% capacitance retention. Therefore, NT-1 binary metal sulfide composite unleashes high-performance supercapacitors with remarkable specific capacitance and cyclic stability.

In-house electrospun La_0.6Sr_0.4Co_0.2Fe_0.8O_3–δ (LSCF) nanofibers have been tested through synchrotron x-ray diffraction and electrochemical impedance spectroscopy (EIS) in the 823–1173 K range, namely in the operating window of intermediate-temperature solid oxide fuel cells. Identical tests have been carried out on commercial LSCF powders, as a control sample. The results demonstrate that the electrospinning manufacturing procedure influences the crystalline properties of the perovskite. The rhombohedral structure (R), stable at room temperature, is retained by nanofibers throughout the whole temperature range, while a rhombohedral to cubic transition (R→C) is detected in powders at ⁓1023 K as a discontinuity in the rhombohedral angle α, accompanied by an abrupt change in oxygen occupation and microstrain. EIS data have a single trend in the nanofibers Arrhenius plot, and two different ones in powders, separated by a discontinuity at the structural transition temperature. Thus, a striking parallel is demonstrated between the variation with temperature of crystallographic features and electrochemical performance. Interestingly, this parallel is found for both nanofiber and granular electrodes. This opens up questions and new perspectives in attributing activation energies derived from EIS tests of LSCF materials to electrochemical processes and/or crystal structure variations.

All-solid-state lithium batteries (ASSB) are emerging as an effective and promising alternative to current technologies that use organic liquid electrolytes. Its main proposition is to mitigate the safety and environmental issues caused by the leakages and explosions of conventional cells through the development and use of solid electrolytes, in the form of polymer membranes, ceramic pellets, or even composites, which are a combination of both. In the present work, composite electrolytes of polyethylene oxide (PEO), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and Zr-doped niobium garnet oxides (Li_5+xLa₃Nb_2-xZr_xO₁₂ - LLNZ) were prepared. The addition of ceramic reduced the melting point and inhibited the formation of spherulite-type crystallization of the polymer. The ionic conductivities of the composites were slightly lower than the polymer but still high for composite electrolytes of this composition, around 10⁻⁴ S.cm⁻¹. The obtained results were analyzed considering the findings reported by other researchers, and some factors for a high-performance composite electrolyte were detailed. Additionally, all the fabricated composites showed a broad electrochemical window, some even above 5.0 V. Thus, electrochemical measurements were conducted with NMC811 as the cathode. The half-cell exhibited a specific capacity of 185 mAh.g⁻¹ at C/20 at 60 °C, and a capacity retention of 68% after 50 cycles at C/5. The results are promising and indicate the possibility of the use of high‑nickel cathodes in all-solid-state batteries to increase their energy density.

In the present work, gadolinium-doped ceria-based powders were co-fired with additions of 1% (w/w) of SiO₂, and 5% (w/w) of Y₂O₃ to test the role of yttrium ion on improving the grain boundary conductivity across the grain boundary regions of low grade gadolinia-doped ceria (CGO) electrolytes. The samples were prepared by hot press at low temperature (1000 °C) to minimize bulk dissolution of yttrium in the CGO lattice. Structural characterization by XRD of the prepared ceramics confirms a CGO single phase material with the fluorite type structure. All the samples were characterized by impedance spectroscopy as a function of temperature in air, in order to de-convolute different microstructural contributions to the overall electrical behaviour. The results showed, as expected, that the presence of small amounts of impurity of silica reduces the total conductivity, when compared with pure CGO ceramic sample. The grain boundary resistance of these ceramics, under low operating temperatures, has a large effect on the total conductivity and is related, on one hand with the presence of a space charge layer created by the local segregation of trivalent rare earth elements, and the consequently depletion of oxygen vacancies, and on the other hand by the blocking effect of the silicon impurity. However, the obtained results show that addition of yttria increases total conductivity when compared with impure samples without yttria. This effect was related with the partial recover of specific grain boundary conductivity, suggesting a preferential location of Si and Y cations on grain boundaries. The space charge potential values, calculated using impedance data, provided an approach to the promoting effect of recovering grain boundary conductivity by the yttrium ion.

In this study, A-site defective Ca_yTi_0.93Sc_0.07O_3-α oxides were prepared to examine their ionic conduction properties. The electrical conductivities of two typical compositions were measured as functions of oxygen partial pressure P_O2, temperature, and humidity. Additionally, phase transition, chemical expansion, and CO₂ tolerance were examined in Ca_0.985Ti_0.93Sc_0.07O_3-α using an atmosphere-controlled high-temperature X-ray diffraction. In Ca_0.947Ti_0.93Sc_0.07O_3-α, the ionic conduction domain over a wide range of P_O2 was observed at 500–800 °C, even though the humidity dependence of conductivities was confirmed only at 500 °C. Conversely, in Ca_0.985Ti_0.93Sc_0.07O_3-α, the conductivities were enhanced in humidified atmospheres at 500–800 °C, while the ionic conductivities in dry atmospheres were higher than those of 8YSZ. As protonic and oxide ionic conductivities are comparable, the proton-oxide ion mixed conduction can be considered to occur in Ca_0.985Ti_0.93Sc_0.07O_3-α. Therefore, a small percentage of Ca defect in Ca_yTi_0.93Sc_0.07O_3-α affects not only conductivity but also conductive ionic species. Furthermore, Ca_0.985Ti_0.93Sc_0.07O_3-α did not show any phase transition and chemical expansion with hydration up to 900 °C. The crystal phase of Ca_0.985Ti_0.93Sc_0.07O_3-α during the CO₂ tolerance test was observed to be stable. Therefore, the material properties of Ca_yTi_0.93Sc_0.07O_3-α suggest its high potential as electrolytes in high temperature electrochemical devices.