Capillary electrophoretic separation of inorganic sulfur-sulfide, polysulfides, and sulfur-oxygen species

A CE protocol was developed for the identification and separation of inorganic polysulfides simultaneously with other inorganic sulfur-bearing species coexisting in aqueous hydrosulfide/sulfur solutions. The electrophoretic separation of thiosulfate, sulfate, hydrosulfide, sulfite, tetrathionate, and polysulfides was achieved at pH values between 8.2 and 12.2. The peaks attributed to the polysulfide species were strongly sensitive to pH. CE analysis of hydrosulfide/sulfur solutions at different pH values permitted possible identification of two forms of polysulfides: S4(2-) and S3(2-). Upon exposure to air at ambient temperature, thiosulfate was the main oxidation product of hydrosulfide/sulfur solutions mainly in the first 60 min, when hydrosulfide was rapidly consumed. Analysis of the oxidation reaction products provided retrospectively tentative evidence that the peaks separated and identified as tri- and tetrasulfide may be ascribed to polysulfides.     

Utilizing the Alterable Solubility of Chitosan in Aqueous Solution to Synthesize Nanosized Sulfur for High Performance Li–S Batteries

We demonstrate the synthesis of cathode material with nanosized sulfur by a precipitation method making use of the alterable solubility of chitosan (CTS) in aqueous solution. Mesoporous Ketjen Black (KB) and carbon nanotube (CNT) are added as conductive agents to provide the three‐dimensional electric channels. This method can reduce the size of the sulfur particles, thus the nanosized sulfur obtained can fully contact with the conductive agent, which could increase the utilization of sulfur and improve the capacity of Li‐S batteries. Moreover, CTS with abundant hydroxyl and amine groups has strong interaction with polysulfides, which can improve the stability of Li‐S batteries. As a result, the obtained CTS/C‐S cathode containing 76 wt% sulfur delivers an impressively initial discharge specific capacity of 1141.6 mA·h·g^–1 at 0.5 C and maintains a capacity of 842.3 mA·h·g^–1 after 300 cycles. Our finding paves a way for the rational design of high‐performance sulfur cathodes for advanced Li‐S batteries.     

Use of polysulfides of alkali and alkaline-earth metals to obtain highly dispersed sulfur

Possibilities of obtaining polysulfides of alkali and alkaline-earth metals in aqueous solutions were considered. The composition of the polysulfides and their concentration in solutions were found. The efficiencies of application of highly dispersed sulfur, produced from calcium polysulfide, and colloid sulfur as a fungicide were compared.     

Chemical precipitation of sulfur nanoparticles from aqueous solutions

Process of formation and coarsening of sulfur nanoparticles deposited from aqueous solutions of calcium and sodium polysulfides and sodium thiosulfate and from solutions of elementary sulfur in a mixture of hydrazine hydrate and monoethanolamine was considered. The sulfur nanoparticles were characterized with a laser analyzer of particle sizes, X-ray diffraction analysis, and electron probe microscopy. It was shown that the sizes of primary particles strongly depend on the concentration of an acid and on the molar ratio between the sulfur-containing solutions and the acid. The antifungal effects of sulfur with nano- and micrometer dimensions were compared. The experimental results demonstrated a strong antifungal effect of sulfur nanoparticles on various kinds of fungi.     

Reasons for the effect of the amount of electrolyte on the performance of lithium–sulfur cells

As is known, the depth of the electrochemical reduction of sulfur and lithium polysulfides, the reduction rate, and the cycle life of lithium–sulfur cells decrease with the electrolyte content. The present paper studies the reasons for the effect of the amount of electrolyte on the depth of sulfur reduction and the cycle life of lithium–sulfur cells. The main reason for the effect of the amount of electrolyte on the depth of the electrochemical reduction of sulfur was shown to be the generation of solvate complexes of lithium polysulfides. The minimum amount of electrolyte required for complete reduction of sulfur during the discharge of lithium–sulfur cells is determined by the composition of the generated solvate complexes of lithium polysulfides. The solvate numbers of the lithium ion in the solvate complexes of lithium polysulfides generted in sulfolane electrolyte systems were evaluated from the experimental data. An analysis of the results shows that the minimum solvate number of lithium ions in the solvate complexes of lithium polysulfides with sulfolane is 1.     

Cycling a Sulfur Electrode in Mixed Electrolytes Based on Sulfolane: Effect of Ethers

The cycling of a sulfur electrode is studied in 1 M LiCF₃SO₃ solutions in sulfolane mixtures with ethers 1,2-dimethoxyethane, dioxolane, and tetrahydrofuran. The results suggest that the electrochemical behavior of sulfur is defined by the forms of existence of lithium polysulfides in the electrolyte.     

介孔碳纳米纤维-硫作为锂硫电池正极材料(英文)

锂硫电池的商用化受到硫和多硫化锂低的电导率、多硫化锂在有机电解液中的溶解、放电过程中硫的体积膨胀等因素的制约。我们通过自模板法制备了具有石墨化孔壁结构的介孔碳纳米纤维(MCNF),并利用这种结构将硫和多硫化锂封装在碳骨架内。具有石墨化孔壁结构的一维MCNF能够在循环中为硫和多硫化锂提供良好的导电网络。MCNF中小的介孔能够抑制长链多硫化锂的扩散。另外,MCNF大的孔容能够负载比较多的硫,并且能够为硫的放电膨胀提供足够的纳米空间。本工作制备的MCNF-硫纳米复合材料在0.8 A·g-1的电流密度下,经过100次循环后仍有820 mAh·g-1的比容量。     

介孔碳纳米纤维-硫作为锂硫电池正极材料

锂硫电池的商用化受到硫和多硫化锂低的电导率、多硫化锂在有机电解液中的溶解、放电过程中硫的体积膨胀等因素的制约。我们通过自模板法制备了具有石墨化孔壁结构的介孔碳纳米纤维（MCNF）,并利用这种结构将硫和多硫化锂封装在碳骨架内。具有石墨化孔壁结构的一维MCNF能够在循环中为硫和多硫化锂提供良好的导电网络。MCNF中小的介孔能够抑制长链多硫化锂的扩散。另外,MCNF大的孔容能够负载比较多的硫,并且能够为硫的放电膨胀提供足够的纳米空间。本工作制备的MCNF-硫纳米复合材料在0.8A·g^-1的电流密度下,经过100次循环后仍有820mAh·g^-1的比容量。     

Oxygen Vacancies on Layered Niobic Acid That Weaken the Catalytic Conversion of Polysulfides in Lithium–Sulfur Batteries

Oxygen vacancies are usually considered to be beneficial in catalytic conversion of polysulfides in lithium–sulfur batteries. Now it is demonstrated that the conversion of polysulfides was hindered by oxygen vacancies on ultrathin niobic acid. The inferior performance induced by the oxygen vacancy was mainly attributed to the decreased electric conductivity as well as the weakened adsorption of polysulfides on the catalyst surface. This work shows that the care should be taken when designing a new catalyst for the lithium–sulfur battery using a defect‐engineering strategy.     

Electrochemical Synthesis of Organic Polysulfides from Disulfides by Sulfur Insertion from S8 and an Unexpected Solvent Effect on the Product Distribution

An electrochemical synthesis of organic polysulfides through sulfur insertion from elemental sulfur to disulfides or thiols is introduced. The highly economic, low-sensitive and low-priced reaction gives a mixture of polysulfides, whose distribution can be influenced by the addition of different amounts of carbon disulfide as co-solvent. To describe the variable distribution function of the polysulfides, a novel parameter, the “absorbance average s ulfur a mount in p olysulfides” (SAP) was introduced and defined on the basis of the “number average molar mass” used in polymer chemistry. Various organic polysulfides were synthesized with variable volume fractions of carbon disulfide, and the yield of each polysulfide was determined by quantitative ¹³C NMR. Moreover, by using two symmetrical disulfides or a disulfide and a thiol as starting materials, a mixture of symmetrical and asymmetrical polysulfides could be obtained.     

乙酰丙酮钛螯合物掺杂丙烯酸酯共聚物水溶胶

乙酰丙酮钛螯合物掺杂丙烯酸酯共聚物水溶胶;乙酰丙酮钛螯合物; 丙烯酸酯共聚物水溶胶;掺杂     

Development of in-house reference materials for determination of inorganic polysulfides in water

In-house reference materials (IHRMs) for determination of inorganic polysulfides in water have been developed. The determination is based on the polysulfides derivatization with a methylation agent followed by GC/MS or HPLC analysis of the difunctionalized polysulfides. Therefore, the IHRMs are synthesized in the form of dimethylated polysulfides containing from four to eight atoms of sulfur. The composition of the compounds is confirmed by NMR and by the dependence of the HPLC retention time of the dimethyl polysulfides on the number of sulfur atoms in the molecule. Stability of the IHRMs is studied by HPLC with UV detection at 230 nm. Carbon tetrachloride solutions of the dimethyl polysulfides are stable at –20°C for 2 weeks, while their solutions in a mixture of acetonitrile and formic acid, 1:1, are stable even at +5°C for 3 weeks. The total sulfur content is controlled by the IHRMs oxidation with perchloric acid in high-pressure vessels (bombes) followed by determination of the formed sulfate using ICP-AES. Certified values of the dimethyl polysulfide concentrations are in the range of 416–3,327 ppm.Presented at the Second International Conference on Metrology—Trends and Applications in Calibration and Testing Laboratories, 4–6 November, 2003, Eilat, Israel     

锂-硫电池研究现状及展望

锂-硫电池由于具有高比能量以及硫廉价易得等优势而受到人们的广泛关注. 但其实际应用仍面临着来自于正极、电解液以及负极等方面的诸多挑战,具体包括硫正极的溶解、多硫化合物的“穿梭效应”及金属锂负极的枝晶问题. 本文以课题组近期的研究结果为主线,综述了近两年来关于锂-硫电池的研究进展,重点探讨了碳硫复合物正极、硫化锂正极、复合隔膜设计和电解液方面的研究进展,并总结了各方面存在的问题.     

氮硫共掺杂多孔碳材料的制备及其在锂硫电池中的应用

锂硫电池因其较高的理论容量和对环境友好等优势被视为极具发展潜力的储能装置,但是多硫化物的穿梭效应极大地限制了锂硫电池的实际应用。本文以葡萄糖为碳源,离子液体为氮源和硫源,KCl和ZnCl₂为模板剂,KOH为活化剂,通过热解工艺合成了氮硫共掺杂多孔碳（NSPC）。XPS和极性吸附实验表明N、S杂原子成功引入并且提高了碳材料对多硫化物的吸附能力,有效缓解多硫化物的穿梭效应,而较高的比表面积（1290.67 m²·g^-1）有助于提高硫负载量。负载70.1wt.%的硫后（S@NSPC）作为锂硫电池的正极材料表现出了良好的电化学性能。在167.5 mA·g^-1的电流密度下S@NSPC的首次放电容量为1229.2 mAh·g^-1,远高于S@PC的861.6 mAh·g^-1,且S@NSPC循环500圈后容量为328.1 mAh·g^-1。当电流密度从3350 mA·g^-1恢复至167.5 mA·g^-1时,可逆容量达到首圈放电比容量的80%,几乎恢复至其初始值。     

硫/多孔碳纳米管复合材料的制备及电化学性能

为了解决单质硫导电性差、充放电过程中体积膨胀、中间产物多硫化物的穿梭效应等问题,将硫负载于一种高比表面积的多孔碳纳米管（PCNTs）,制备了S/PCNT复合材料,研究了其电化学性能。相比于S/CNT,S/PCNT的电化学性能有明显提升,这可归因于S/PCNT中的嵌入结构,为硫在充放电过程中的体积膨胀提供了缓冲空间,避免了硫与电解液的直接接触,进而有效限制多硫化物的溶解,从而缓解多硫化物的穿梭效应,使硫正极具有更好的循环稳定性。     

锆螯合物交联丙烯酸酯共聚物无皂水溶胶的研究Ⅱ锆螯合物与丙烯酸酯三元共聚物无皂水溶胶的交联反应

研究了三元丙炮酸酯共聚物（MMA／BA／AA）无皂水溶液中加入三乙醇胺锆螯合物对水溶胶及涂膜性能的影响，在水溶胶中，螯合物增加了共聚物的亲水性，改变了水溶胶的流变性、稳定性、表面张力、螯合物也提高了共聚物涂膜的耐水性，X光电子能谱（XPS）研究表明，在固化成膜过程中螯合物与共聚物发生交联反应，用IR、^1HNMR、DSC、TGA和UV等方法对其交联机理作了初步探讨。     

Kinetics and Mechanism of low-Temperature Oxidation of H2S with Oxygen in the gas Phase

The possibility of the formation of polysulfides during oxidation of H₂ S with oxygen on oxide catalysts has been checked, and the sequence of the reaction stages at temperatures below the sulfur dew point determined. The amount of polysulfides formed during H₂ S oxidation has been found to exceed significantly that obtained in the reaction of sulfur with H₂ S. Polysulfides are concluded to be intermediates in H₂ S oxidation to sulfur. The rate of formation of SO₂ from sulfur vapor is shown to be negligibly low at 100-200°C. A reaction scheme involving the formation of sulfur from polysulfides and the formation of sulfur dioxide by direct oxidation of H₂ S is suggested.     

V2O5空心球作为高效硫载体用于锂硫电池（英文）

以V2O5空心球作为锂硫电池的正极材料,将其用于存储硫和限制多硫化物的穿梭效应。V2O5空心球的平均直径约为500 nm,为存储硫提供了更多空间并适应硫电极的体积变化。同时,V2O5对多硫化物具有很强的化学吸附性,可以有效地限制多硫化物的穿梭效应。由于中空结构增加了硫的存储,并通过化学键牢固地吸附多硫化物,使该锂硫电池同时具有高容量和良好的稳定性。V2O5/S作为正极的锂硫电池在0.1C倍率时显示出1439 mAh·g-1的高可逆容量,并在1C的倍率下循环300次后的容量约为600 mAh·g-1。     

系列烷基多硫化物形成的摩擦膜和热膜的XANES分析

采用X射线吸收精细结构光谱(XANES)对不同硫含量的系列烷基多硫化物与钢表面在70 ℃和150 ℃反应的热膜以及摩擦膜进行了分析. 结果表明, 在70 ℃和150 ℃下生成的热膜的主要成分是FeSO4或Fe2(SO4)3, 温度的升高会增大生成的热膜厚度; 生成的摩擦膜成分主要是铁的硫酸盐、二硫化铁和亚砜的混合物. 添加剂分子中硫含量的提高可以增大生成的热膜和摩擦膜的厚度.     

Coprecipitation of Nanocomposites Based on Colloidal Particles of Sulfur and Carbonates of Alkaline-Earth Metals from Polysulfide Solutions

It has for the first time been shown that the action of carbon dioxide on solutions of alkaline-earth metal polysulfides causes a reaction yielding nanoparticles of sulfur and calcium, barium, and strontium carbonates. It has been found that, initially, particles of sulfur and a corresponding carbonate are synthesized with average sizes of about 20–25 nm; then, the particles are enlarged (aggregated) with the precipitation of a composite, which consists of hydrophobic particles of sulfur and the carbonate (the latter become hydrophobic due to the adsorption of neonol present in the reaction mixture). It has been shown that only sulfur exhibits antifungal activity in the composites, while carbonates have no effect on pathogenic fungi. The composite consisting of sulfur and calcium carbonate nanoparticles has shown the highest biological activity during germination of wheat seeds.