二次锂电池聚合物正极材料研究进展

近几十年,二次锂电池作为重要的储能装置得到迅猛发展,而开发高性能的锂电池电极材料一直是电化学能源领域的研究热点之一。与传统无机正极材料相比,聚合物正极材料具有比容量高、柔软性好、廉价易得、环境友好、加工方便、可设计性强等诸多优点。本文综述了导电聚合物、共轭羰基聚合物以及含硫聚合物正极材料的结构特点、电极反应机理、电化学性能和近五年来的重大研究进展,总结了这三类聚合物电极材料的优缺点,并重点介绍了含硫聚合物电极材料中存在的问题及改进手段,最后提出了综合这三类聚合物优点的含硫共轭导电聚合物将会是该领域的研究方向。     

Enhancing effect of boron trifluoride diethyl etherate electrolytes on capacitance performance of electropolymerized poly[poly(<Emphasis Type="Italic">N</Emphasis>-vinyl-carbazole)] films

In this paper, poly[poly(N-vinyl-carbazole)] (PPVK) films electrodeposited in tetrahydrofuran (THF) containing 12 % boron trifluoride diethyl etherate (BFEE) were studied as electrode active material for supercapacitors. The morphology and thermal property were characterized by SEM, atomic force microscopy (AFM), and thermogravimetry (TG), respectively. The electrochemical capacitive behaviors of the PPVK films were also investigated by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The electrochemical results showed that the specific capacitance of PPVK films in CH₃CN solution was about 126 mF cm^?2 at 1.5 mA cm^?2 and the capacitance retention was only 14.4 % after 1000 cycles. It was exciting to improve the specific capacitance up to 169.3 mF cm^?2 at 1.5 mA cm^?2 and to make the cyclic stability increase to 81.8 % capacitance retention after 5000 cycles when the equivalent BFEE was added into the CH₃CN solution containing 0.05 M Bu₄NBF₄ electrolyte. These results clearly demonstrated that BFEE was an efficient promoter for the enhancement of the capacitance performance of PPVK films. Therefore, with the help of BFEE electrolyte, the PPVK films have potential application as capacitive materials in high-performance energy storage devices.     

One-pot fabrication of single-crystalline octahedral Pd-Pt nanocrystals with enhanced electrocatalytic activity for methanol oxidation

This study reports the synthesis of octahedral Pd-Pt bimetallic alloy nanocrystals through a facile, one-pot, templateless, and seedless hydrothermal method in the presence of glucose and hexadecyl trimethyl ammonium bromide. The morphologies, compositions, and structures of the Pd-Pt nanocrystals were fully characterized by various physical techniques, thereby demonstrating their highly alloying octahedral nanostructures. The formation or growth mechanism of the Pd-Pt bimetallic alloy nanocrystals was explored and is discussed here based on the experimental observations. In addition, the synthesized Pd-Pt nanocrystals were applied to the methanol oxidation reaction (MOR) in alkaline media, which proved that the as-prepared catalysts exhibit enhanced electrocatalytic activity for MOR. Pd₁Pt₃ exhibited the best stability and durability, and its mass activity was 3.4 and 5.2 times greater than those of Pt black and Pd black catalysts, respectively. The facile synthetic process and excellent catalytic performance of the as-prepared catalysts demonstrate that they have the potential to be used in direct methanol fuel cell techniques.     

Ultra-high surface area and mesoporous N-doped carbon derived from sheep bones with high electrocatalytic performance toward the oxygen reduction reaction

A nitrogen (N)-doped mesoporous carbon material exhibiting ultra-high surface area was successfully synthesized from sheep bones via a facile and low-cost method. The obtained carbon material had an ultra-high specific surface area of 1961 m² g^?1 and provided rich active sites for the oxygen reduction reaction (ORR), which in turn resulted in high electrocatalytic activity. It was found that the pore size distribution for the newly prepared carbonaceous material fell in the range of 1–4 nm. Benefiting from its high surface area and the presence of pyridine-N and quaternary-N species, the as-prepared carbon material exhibited excellent ORR activity in an oxygen-saturated 0.1 M KOH solution, compared to commercial Pt/C (10 wt%). Due to its high ORR catalytic activity, stability and low-cost, using sheep bone as C and N precursors to produce N-doped carbon provides an encouraging step toward the goal of replacing commercial Pt/C as fuel cell cathode electrocatalyst.     

Preparation and thermal reliability of <Emphasis Type="Italic">N</Emphasis>-butyl stearate/methyl palmitate composite phase change material

In this study, a series of binary mixtures of N-butyl stearate (nBS) and methyl palmitate (MP) were used to produce a novel composite phase change material (CPCM) for potential application in the eastern China, and their thermal properties were investigated by differential scanning calorimetry (DSC). The results of DSC indicated that the mixture consisting of 10 mass% nBS and 90 mass% MP is optimum as the CPCM in terms of the phase change temperature ranges (T _f = 19.74–5.59 °C; T _m = 18.34–33.80 °C) and latent heats (ΔH _f = 176.8 J g^?1; ΔH _m = 189.3 J g^?1). On the other hand, the thermal reliability and chemical stability of the CPCM after 120, 180, 240, 300, 360 and 500 accelerated thermal cycling tests were studied by DSC and fourier transform infrared (FTIR) analysis. The results demonstrated that the CPCM had good thermal reliability and chemical stability.     

Syntheses and photocatalytic performances of four coordination complexes constructed from 1,10-phenanthroline and polycarboxylic acids

Four coordination complexes of copper(II) and iron(II), namely [CuCl(phen)₂](5-NO₂-Hipa)·2H₂O (BUC-10), [Cu(phen)(3,4-H₂dczpb)(H₂O)]·H₂O (BUC-11), [Fe(phen)(L)(H₂O)]₂ (BUC-12), and [Fe(phen)₃](3,4-H₃dczpb)₂·0.6H₂O (BUC-13) (phen = 1,10-phenanthroline; 5-NO₂-H₂ipa = 5-nitroisophthalic acid; 3,4-H₄dczpb = 3,4-dicarboxyl-(3′,4′-dicarboxylazophenyl) benzene; L = 6,12-dihydroxy-1,2,6,12-tetrahydroindazolo[2,1-a]indazole-1,7-dicarboxylic acid), have been synthesized under hydrothermal conditions. All four complexes were characterized by single-crystal X-ray diffraction, FTIR, elemental analysis and UV–Vis diffuse reflection spectroscopy. The photocatalytic performances of the complexes for decomposition of methylene blue under UV irradiation were also investigated.     

Improved synthesis and low-temperature performance of a series of saturated α-branched fatty acids

Five saturated α-branched fatty acids, also known as Guerbet acids, including α-propylhexyl acid (G ₁ ), α-butylhexyl acid (G ₂ ), α-propyloctyl acid (G ₃ ), α-butyloctyl acid (G ₄ ), and α-hexyloctyl acid (G ₅ ), were synthesized in high yields by four-step reaction. Colorless, almost odorless, and oily products were obtained with high purity, whose structures were confirmed by GC, ¹H/¹³C NMR, and ESI–MS characterization. G ₁ , G ₃ , and G ₄ had pour points lower than ?60 °C, while G ₂ and G ₅ showed higher pour points (?42 °C and 6 °C, respectively) because of their molecular symmetry. Considering the low-temperature properties, G ₁ , G ₃ , G ₄ , and even G ₂ held great potential applications in the lubricant and oilfield.     

Effect of surface chemical modification for aluminum hypophosphite with hexa‐(4‐aldehyde‐phenoxy)‐cyclotriphosphazene on the fire retardancy,water resistance,and thermal properties for polyamide 6

The surface chemical modified aluminum hypophosphite (AHP) defined as MAHP was successful prepared through P–H bonds on AHP surface reacted with the aldehyde groups in hexa‐(4‐aldehyde‐phenoxy)‐cyclotriphosphazene made in our lab. The wettability of the flame retardants was evaluated by water contact angle tests, and the water contact angle of the prepared MAHP dramatically increased from 0° for AHP to 145°, which indicated the surface modification made the superhydrophilic AHP into superior hydrophobic MAHP. The prepared MAHP and AHP, respectively, incorporated into polyamide 6 (PA6) matrix to prepare flame retardant PA6 composites and the fire retardancy and thermal degradation behavior of flame retardant PA6 composites were investigated by limiting oxygen index, vertical burning test (UL‐94), cone calorimeter, and thermogravimetric analysis tests. The morphologies and chemical compositions of the char residues for PA6 composites were investigated by scanning electron microscopy and X‐ray photoelectron spectroscopy, respectively. The water resistant properties of flame retardant PA6 composites were evaluated by putting the samples into distilled water at 70°C for 168 hr, and the mechanical properties for flame retardant PA6 composites were investigated by the tensile, flexural, and Izod impact strength tests. The results demonstrated that the PA6/MAHP composites successfully passed UL‐94 V‐0 flammability rating, and the limiting oxygen index value was 27.6% when the loading amount of MAHP was 21 wt%. However, there is no rating in vertical burning tests for PA6/AHP composite with the same amount of AHP, which indicated the surface modification of AHP enhanced the flame retardancy efficiency for PA6 composites. The morphological structures and analysis of X‐ray photoelectron spectroscopy of char residues revealed that the surface modification of AHP benefited to the formation of a sufficient, flame retardant elements rich, more compact and homogeneous char layer on the materials surface during combustion, which prevented the heat transmission and diffusion, limit the production of combustible gases, inhibit the emission of smoke and then led to the reduction of the heat release rate and smoke produce rate. The mechanical properties results revealed that the surface modification of AHP enhanced the mechanical properties, especially the Izod impact strength comparing with that of PA6/AHP composites with the same amount of flame retardant. After water resistance tests, the PA6/MAHP composites remained superior flame retardancy and presented continuous and compact char layer after cone calorimeter tests; however, the fire retardancy for PA6/AHP composite obviously decreased, and the char layer was discontinuous with big hole caused by the extraction of AHP by water during water resistance tests. Copyright © 2017 John Wiley & Sons, Ltd.     

新型BT-BMT-xBNT无铅高储能密度陶瓷研究

本文采用传统固相反应法,成功制备了新型无铅弛豫铁电陶瓷(1-x)[0.9BaTiO₃-0.1Bi(Mg_0.25Ta_0.5)O₃]-xBi_0.5Na_0.5TiO₃。结果表明,较高居里温度的Bi_0.5Na_0.5TiO₃的引入,使得材料体系中建立了更多的以Bi—O耦合为主的极性纳米区域,弥补了因Bi(Mg_0.25Ta_0.5)O₃的加入导致的宏观极化强度的减少,提高了材料的饱和极化强度,实现了较高储能密度的同时具有更好的温度稳定性。在245 kV/cm电场强度下,x=0.2样品的储能密度约为4.01 J/cm³,储能效率约为84.86%,同时该组分在20~170 ℃储能密度的变化率小于5%,储能效率的变化率小于6%,表现出优异的温度稳定性。     

钙钛矿结构RFeO3晶体的磁化跃迁效应研究进展

钙钛矿稀土正铁氧体RFeO3具有丰富的磁性,这主要源于4f电子层的稀土离子和3d电子层的铁离子之间复杂的相互作用.磁化跃迁作为RFeO3体系中的重要现象,是指体系中的稀土离子磁矩和铁离子磁矩在特定的磁场和温度下发生180°旋转,宏观表现为磁热曲线中磁化强度发生断崖式变化.本文综述了不同化合物RFeO3的两种磁化跃迁现象...