Journal of Solid State Electrochemistry最新文献

Due to its superior high discharge capacity and cycling stability, single-crystal LiNi_0.6Co_0.2Mn_0.2O₂ cathode materials are rapidly gaining traction in the realm of electric vehicle power batteries. Nevertheless, the deterioration of surface structure in single-crystal LiNi_1−x−yCo_xMn_yO₂ cathode materials is further exacerbated when operating at higher cutoff voltages (exceeding 4.5 V). In this work, a unique single-crystal LiNi_0.6Co_0.2Mn_0.2O₂ with ZnO and AlPO₄ dual-coating modification has been synthesized. The similar crystal structure of ZnO and NCM results in a more compact coating, while the incorporation of AlPO₄ enhances both the electronic conductivity (through the formation of conductive oxide Al-doped ZnO) and lithium-ion conductivity (via the formation of Li₃PO₄) within the coating. The coated SC-NCM cathode material exhibits excellent electrochemical performance even when operated at a higher cutoff voltage of 4.5 V. After 100 cycles (1 C, 2.75–4.5 V), the capacity retention for the ZnO and AlPO₄ coated SC-NCM sample reaches 91.2%, significantly surpassing that of the pristine samples (40.0%). Specifically, it exhibited an outstanding rate property, maintaining a discharge capacity of 150.8 mA h g⁻¹ at 8 C. The exceptional electrochemical properties can be attributed to the distinctive coating layer, which serves not only as a physical barrier to mitigate electrolyte side reactions but also facilitates rapid conduction of electrons and lithium ions.

In this paper, a 150-µm-thick flexible γ-Al₂O₃ nanofiber separator with the tensile strength of 0.22 MPa was prepared from the low-cost aluminum chloride hydroxide/polyvinyl alcohol (PVA)/water precursor materials by electrospinning method. The resultant separator with 3D interconnection nanostructure revealed fiber diameters in the range of 200 to 500 nm. The specific surface area, porosity, and electrolyte uptake of γ-Al₂O₃ nanofiber separator are 31.5 m²/g, 55%, and 1021%, higher than that of commercial polypropylene (PP) separator and glass fiber (GF) separator. The supercapacitor assembled with the γ-Al₂O₃ nanofiber separator exhibited a high discharge specific capacitance of 93 F/g at the current density of 1A/g, and there is almost no capacity decay after 10,000 cycles. The energy density of supercapacitor assembled with γ-Al₂O₃ nanofiber separator is 31.7 Wh/kg at the power density of 562.6 W/kg. Meanwhile, the rate performance of the supercapacitor is improved significantly due to the existence of porous structure and low ion diffusion resistance (0.78 Ω) of γ-Al₂O₃ nanofiber separator. In addition, the thermal performance of the γ-Al₂O₃ nanofiber separator is also excellent, which has almost no shrinkage at the temperature of 200 °C and cannot be ignited. Therefore, the obtained γ-Al₂O₃ nanofibers could serve as a promising alternative separator for a new generation of safe, high-power supercapacitors.

A new electrochemical sensor for the highly sensitive and selective determination of dopamine was developed, based on the use of a glassy carbon electrode modified with cobalt(II) polymer. Both electrochemical and morphological characterizations were investigated. Square wave voltammetry (SWV) was used for the determination of dopamine. From the SWV results obtained on the modified electrode under the optimized conditions, the successive addition of dopamine increased the anodic peak current. The results obtained show a linear response of the electrode modified with Co(II) polymer in a wide concentration range. Each concentration decade is characterized by a new calibration plot with a corresponding mathematical expression. The highest sensitivity (13.182) was obtained for the lowest concentration range, and the detection limit of 0.03 µM, calculated based on the 3 × s_b/m criterion, indicates a very high sensitivity and great application potential. When analyzing a real sample, the modified electrode showed good electroanalytical activities in terms of oxidation of dopamine, good anti-interference ability, stability, reproducibility, and potential applicability in commercial pharmaceutical samples.

Herein, the novel organic catalyst, (E)-2-cyano-3-(5-(1-methyl-2-(naphthalen-1-yl)-1H-indol-3-yl)furan-2-yl)acrylic acid (8), was designed and synthesized. Initially, novel indole-cyanoacetic acid was prepared by using the Sonogashira coupling reaction, iodocyclization reaction, Suzuki–Miyaura coupling reaction, and condensation reactions. Then, electrochemical studies were carried out to investigate the anode electrocatalyst performance. Electrochemical techniques, including cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in a 1 M KOH + 0.5 M N₂H₄ solution, were employed to determine the hydrazine electro-oxidation performance of the catalyst (8). In addition, theoretical calculations were used to find band gap energies. Our D-A type organic catalyst (8) exhibits very high catalytic activity with 24.67 mA/cm². D-A organic systems were shown to have the potential to be ecologically benign anode catalyst materials for hydrazine fuel cell applications.

Olivine-type lithium manganese iron phosphate (LMFP) has been a promising cathode for Li-ion batteries (LIB) owing to its superior safety performance and low cost, yet the intrinsic low ionic/electronic conductivities result in large electrochemical polarization and inferior rate performance. Herein, we report a LMFP with high-power Li-storage capability through a Na/Co co-doped strategy. The Na⁺ with a larger ionic radius (1.02 Å) locates at Li-sites, effectively widening the Li⁺ diffusion channel to improve the Li-ion transfer dynamic. The Co²⁺ located at transition metal sites (TM-sites) can lower the band gap to improve the electronic conductivity, while it can also alleviate the increase in the b-axis parameter to shorten the Li⁺ transfer path. Accordingly, the concurrently improved ionic/electronic transfer rate endows the superior rate performance of LMFP, with a high reversible capacity of 113.5 mAh g⁻¹ at 5 C, much higher than the pristine sample (only 79.5 mAh g⁻¹). The modified LMFP also displays excellent cycling stability, maintaining 97.1% of its initial capacity after 1000 cycles at 1 C.

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Bismuth ferrite, whose formula is BiFeO₃ (BFO), is widely studied for its photovoltaic and photocatalytic properties. In this study, samples of this material were synthesized using the microwave-assisted hydrothermal method with the aim of measuring its ability to discolor contaminants present in water in previously formulated concentrations through photocatalysis. Photocatalysis is a process with great potential for applicability in the decontamination of effluents. The analysis process used a 1:1 molar ratio of bismuth nitrate to iron nitrate, with the addition of potassium hydroxide to the aqueous solution. Two samples were synthesized at different temperatures, specifically 140 °C and 160 °C. An X-ray diffraction analysis revealed that the synthesized samples were in an amorphous state. Photocatalytic tests were carried out to evaluate the ability of these materials to decolorize rhodamine B present in water in a previously known proportion. A sample synthesized at 140 °C successfully decolorized the solution within 60 min, providing its potential application in photocatalytic processes for decolorization of organic substances from wastewater. In turn, a sample synthesized at 160 °C discolored or contaminated in a slightly longer time. The samples were also subjected to a temperature of 750 ºC until crystallinity was reached. However, photocatalytic tests with crystalline samples performed less well than amorphous samples.

Co-free and Ni-rich LiNi_0.95Mn_0.05O₂ (NM95) cathodes are expected to be widely employed in power batteries due to their high charge storage capacity and cost-effectiveness. However, the loss of Co and increase in Ni contents result in highly active surfaces and unstable structures, compromising rate capability and cyclic stability. Herein, polyaniline-polyethylene glycol (PANI-PEG) coating layer, with excellent electronic and Li-ion conductivity, is introduced on NM95 surface to enhance charge transfer properties and cyclic stability. Several material and electrochemical characterization techniques, such as XRD, SEM, EDS, TEM, XPS, 4-point probe, CV and EIS, are utilized to unveil the positive influence of PANI-PEG on electrochemical performance. The results reveal that PANI-PEG layer can promote electron and Li⁺ conduction of NM95 due to the excellent electronic and Li⁺ conductivities. Besides, PANI-PEG acts as protective layer to hinder the corrosion of electrolyte and suppress side reactions. It is revealed that NM95 cathode coated with PANI-PEG with a mass ratio of 4/6, exhibits excellent initial capacity, as high as 219.4 and 163.1 mAh/g at 1 C and 5 C, respectively, and maintains capacity retention of 94.7% (1 C, 100th cycle) and 79.0% (5 C, 200th) under cut-off voltage of 4.3 V (vs. Li/Li⁺). Moreover, NM95 exhibits capacity retention of 70.7% after 100 charge/discharge cycles at 1 C within voltage range of 2.7 to 4.5 V (vs. Li/Li⁺). These results indicate that coating electronic/Li⁺ conductor is effective strategy to enhance rate performance and cyclic stability of Co-free and Ni-rich cathodes.