表面限域掺杂提升高比能正极材料稳定性

Lithium ion batteries (LIBs) have broad applications in a wide variety of a fields pertaining to energy storage devices. In line with the increasing demand in emerging areas such as long-range electric vehicles and smart grids, there is a continuous effort to achieve high energy by maximizing the reversible capacity of electrode materials, particularly cathode materials. However, in recent years, with the continuous enhancement of battery energy density, safety issues have increasingly attracted the attention of researchers, becoming a non-negligible factor in determining whether the electric vehicle industry has a foothold. The key issue in the development of battery systems with high specific energies is the intrinsic instability of the cathode, with the accompanying question of safety. The failure mechanism and stability of high-specific-capacity cathode materials for the next generation of LIBs, including nickel-rich cathodes, high-voltage spinel cathodes, and lithium-rich layered cathodes, have attracted extensive research attention. Systematic studies related to the intrinsic physical and chemical properties of different cathodes are crucial to elucidate the instability mechanisms of positive active materials. Factors that these studies must address include the stability under extended electrochemical cycles with respect to dissolution of metal ions in LiPF₆-based electrolytes due to HF corrosion of the electrode; cation mixing due to the similarity in radius between Li⁺ and Ni²⁺; oxygen evolution when the cathode is charged to a high voltage; the origin of cracks generated during repeated charge/discharge processes arising from the anisotropy of the cell parameters; and electrolyte decomposition when traces of water are present. Regulating the surface nanostructure and bulk crystal lattice of electrode materials is an effective way to meet the demand for cathode materials with high energy density and outstanding stability. Surface modification treatment of positive active materials can slow side reactions and the loss of active material, thereby extending the life of the cathode material and improving the safety of the battery. This review is targeted at the failure mechanisms related to the electrochemical cycle, and a synthetic strategy to ameliorate the properties of cathode surface locations, with the electrochemical performance optimized by accurate surface control. From the perspective of the main stability and safety issues of high-energy cathode materials during the electrochemical cycle, a detailed discussion is presented on the current understanding of the mechanism of performance failure. It is crucial to seek out favorable strategies in response to the failures. Considering the surface structure of the cathode in relation to the stability issue, a newly developed protocol, known as surface-localized doping, which can exist in different states to modify the surface properties of high-energy cathodes, is discussed as a means of ensuring significantly improved stability and safety. Finally, we envision the future challenges and possible research directions related to the stability control of next-generation high-energy cathode materials.     

含硫高折射率光学树脂合成及性能研究进展

作为无机玻璃的替代品,有机光学树脂具有轻质、抗冲击性好、易加工和可调性强等优点。折射率是光学树脂的主要参数之一,折射率的高低可直接影响成品镜片的厚度、美观性和舒适度。在不降低光学树脂综合性能的基础上提升光学树脂折射率一直是该领域的热点和难点,在光学树脂中引入高摩尔折射率的硫元素被认为是最有效和常用的方法之一。本文将含硫光学树脂分为烯烃类、环氧类、环硫类、多环类和聚氨酯类,简要综述了国内外近几年的研究进展,涉及单体合成、单体聚合以及单体结构对光学树脂综合性能影响,系统总结了以上材料的特性及发展。     

熔盐电化学还原二氧化碳制备碳材料研究进展北大核心CSCD

二氧化碳浓度持续升高导致的温室效应已在全球范围内引发极端天气、冰川融化等一系列生态环境问题。为降低二氧化碳含量,改善气候变暖带来的恶劣影响,研发高效、绿色、安全的二氧化碳处理技术,促进碳资源循环可持续发展刻不容缓。熔盐离子液体作为一种良好的电化学转化介质,为二氧化碳还原提供了一条极具应用前景的技术路线。综述了国内外近几年高温熔盐中二氧化碳的捕获与电化学还原的研究,简述了熔盐电沉积碳的电化学机理和热力学机制,对不同形貌高附加值碳材料:无定形碳、碳球和碳纳米管的制备进行了总结,最后对未来发展方向做出展望。     

High-entropy transition metal chalcogenides as electrocatalysts for renewable energy conversion

High-entropy transition metal chalcogenides (HE-TMCs) are advantageous in electrocatalytic applications compared to other entropy-stabilized systems owing to the greater orbital extension and energetic match of p-orbitals in chalcogenides with d-orbitals of the transition metals providing additional space to tailor their electronic structure. The high-configurational entropy of HE-TMCs leads to stabilization of cubic rock salt, wurtzite-type and hexagonally packed 2D structures. Due to the multi-element nature of HE-TMCs, the synergy among different elements results in tunable d- and p-band positions. As a consequence, the adsorption energies of electrocatalytic reaction intermediates can be tailored to enhance catalytic performance in water splitting and CO₂ reduction. Furthermore, the entropy-stabilized disordered microstructural state of the material endows HE-TMCs with improved corrosion resistance. Despite recent advances in HE-TMC electrocatalysis, challenges such as identification and synthesis of efficient HE-TMCs as well as the identification of catalytically active sites and reaction mechanisms on HE-TMCs remain to be investigated.     

Pipette vial dispersive liquid–liquid microextraction combined with high‐performance liquid chromatography for the determination of benzoylurea insecticide in fruit juice

A simple, sensitive, and efficient method of using a pipette vial to perform dispersive liquid–liquid microextraction based on the solidification of floating organic droplets was coupled with high‐performance liquid chromatography (HPLC) and a diode array detector for the preconcentration and analysis of four benzoylurea insecticides in fruit juice. In this method, 1‐dodecanol was used as an extractant, and a snipped pipette was used as an experimental vial to simplify the procedure of collecting and separating solidified extractant. The experimental parameters were optimized using a Plackett–Burman design and one‐factor‐at‐a‐time method. Under the optimal conditions in the water model, the limits of detection for analytes varied from 0.03 to 0.28 μg/L, and the enrichment factors ranged from 147 to 206. Linearity was achieved for diflubenzuron and flufenoxuron in a range of 0.5–500 μg/L, for hexaflumuron in a range of 1–500 μg/L, and for triflumuron in a range of 5–500 μg/L. The correlation coefficients for the analytes ranged from 0.9986 to 0.9994 with recoveries of 91.4–110.9%. Finally, the developed technique was successfully applied to fruit juice samples with acceptable results. The relative standard deviations of the analytes at two spiking levels (50 and 200 μg/L) varied between 0.2 and 4.5%.     

Extraction of quinolones from milk samples using bentonite/magnetite nanoparticles before determination by high‐performance liquid chromatography with fluorimetric detection

In this work, bentonite magnetic nanoparticles synthesized by a typical coprecipitation method were used as the adsorbent for the magnetic solid‐phase extraction of six quinolones (ciprofloxacin, difloxacin, enrofloxacin, norfloxacin, sarafloxacin, and lomefloxacin) from milk samples followed by high‐performance liquid chromatography with fluorimetric detection. Under the optimized conditions, the linear quantitation range for the six quinolones was 0.3–200 ng/mL, and the correlation coefficients of the calibration curves ranged from 0.9994 to 0.9999. The detection limit of the method was 0.1 ng/mL. Recoveries of quinolones from pure and low‐fat spiked milk samples varied from 80.4 to 92.7% and from 81.3 to 93.5%, respectively. These results demonstrated that the proposed method for the determination of six quinolones in milk samples was rapid, reliable, and efficient.     

Electrospun polystyrene nanofibers as a novel adsorbent to transfer an organic phase from an aqueous phase

The aim of this work is to develop a simple phase‐transfer method for dispersive liquid–liquid microextraction. For this purpose, a polystyrene nanofiber was prepared by a facile electrospinning strategy and used for the first time as an adsorbent to transfer the organic phase in dispersive liquid–liquid microextraction procedure. The fiber was characterized and its chemical stability and excellent hydrophobicity enable it to selectively adsorb the organic solvent in an aqueous sample. High porosity and specific surface area provide a large adsorption capacity. Under the optimal conditions, the developed dispersive liquid–liquid microextraction with high‐performance liquid chromatography method was successfully applied to the analysis of aldehydes in environmental water samples. The merits of this approach are that it is easy‐to‐operate, low‐cost, time‐saving, and has satisfactory sensitivity. It provides an alternative way for fast and convenient phase transfer of the hydrophobic organic solvent from the aqueous phase.     

Identification of chemical constituents in traditional Chinese medicine formula using HPLC coupled with linear ion trap‐Orbitrap MS from high doses of medicinal materials to equivalent doses of formula: Study on Xiang‐Sha‐Liu‐Jun‐Zi‐Jia‐Jian granules

High‐resolution mass spectrometry has been a powerful tool for the research of chemical constituents in traditional Chinese medicine (TCM) formulas. However, the chromatographic peaks were difficult to discriminate clearly in data collection or analysis because of the complexity and the greatly different content of the constituents in TCM formula, which increased the difficulty of identification. In this study, a high‐performance liquid chromatography coupled with linear ion trap‐Orbitrap mass spectrometry based strategy focused on the comprehensive identification of TCM formula constituents was developed. Identification was carried out from a high dose of medicinal materials to equivalent dose of formula. Meanwhile, combined with mass spectrometry data, chromatographic behaviors, reference standards and previous reports, the identification of constituents in Xiang‐Sha‐Liu‐Jun‐Zi‐Jia‐Jian granules was described. 169 compounds were unambiguously or tentatively characterized, mainly including flavonoids, alkaloids, triterpenic acids, triterpene saponins, lactones, sesquiterpenoids and some other compounds. Among them, 11 compounds were unambiguously confirmed by comparing with reference standards. These results demonstrated that the method was effective and reliable for comprehensive identification of constituents of Xiang‐Sha‐Liu‐Jun‐Zi‐Jia‐Jian granules extracts and reveal the material basis of its therapeutic effects. This strategy might propose a research idea for the characterization of multi‐constituents in TCM formula.     

Chiral separation of brompheniramine enantiomers by recycling high‐speed countercurrent chromatography using carboxymethyl‐β‐cyclodextrin as a chiral selector

A recycling high‐speed countercurrent chromatography protocol was proposed for the enantioseparation of brompheniramine by employing β‐cyclodextrin derivatives as a chiral selector. The two‐phase solvent system of n‐hexane/isobutyl acetate/0.10 mol/L phosphate buffer solution with a volume ratio of 2:4:6 was selected by a series of extraction experiments. Factors that affected the distribution of the enantiomers over the two‐phase system (e.g., the type and concentration of β‐cyclodextrin derivatives = pH value of the aqueous solution, and the separation temperature) were also investigated. In addition, the theory of thermodynamics is applied to verify the feasibility of the enantioseparation process and the corresponding results demonstrate that this separation process is feasible. The optimized conditions include carboxymethyl‐β‐cyclodextrin concentration of 0.010 mol/L, pH of 7.5, and temperature of 5°C. Under the optimal conditions, the purities of both monomer molecules were over 99%, and the recovery yields were 88% for (+)‐brompheniramine and 85% for (–)‐brompheniramine, respectively.