PEO基聚合物电解质及其锂硫电池性能研究

锂硫电池由于具有高的理论比能量引起了广泛关注,然而传统液态锂硫电池由于多硫化物的“穿梭效应”以及安全问题而限制了其应用,全固态锂硫电池可显著提高电池安全性能并有望解决多硫化物的穿梭问题. 本文采用传统的溶液浇铸法制备了具有不同的[EO]/[Li⁺]的PEO-LiTFSI聚合物电解质,并将其应用于锂硫电池. 研究发现,虽然[EO]/[Li⁺] = 8的聚合物电解质具有更高的离子电导率,但是[EO]/[Li⁺] = 20的电解质与金属锂负极间的界面阻抗更低,界面稳定性更好. Li|PEO-LiTFSI([EO]/[Li⁺]=20)|Li对称电池在60 °C,电流密度为0.1 mA·cm^-2时可稳定循环超过300 h,而Li|PEO-LiTFSI ([EO]/[Li⁺]=8)|Li对称电池循环75 h就出现了短路现象. 基于PEO-LiTFSI([EO]/[Li⁺]=20)电解质的锂硫电池首圈放电比容量为934 mAh·g^-1,循环16圈后放电比容量为917 mAh·g^-1以上. 而基于PEO-LiTFSI ([EO]/[Li⁺]=8)电解质的锂硫电池,由于与锂负极较低的界面稳定性不能够正常循环,首圈就出现了严重过充现象.     

Ni3S2@碳纳米管复合材料的制备及其储钠性能

采用一步固相煅烧工艺制备了碳纳米管原位封装Ni₃S₂纳米颗粒（Ni₃S₂@CNT）,并研究了其作为钠离子电池（SIBs）负极材料的电化学性能. 通过X射线衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、循环伏安测试、恒流充放电以及交流阻抗等研究了Ni₃S₂@CNT的物相结构、形貌特征以及电化学性能. 电化学测试表明,材料在100 mA·g ^-1电流密度下,放电容量可以达到541.6 mAh·g ^-1,甚至在2000 mA·g ^-1的大电流密度下其放电比容量也可以维持在274.5 mAh·g ^-1. 另外,材料在100 mA·g ^-1电流密度下,经过120周充放电循环后其放电和充电比容量仍然可以保持在374.5 mAh·g ^-1和359.3 mAh·g ^-1,说明其具有良好倍率性能和循环稳定性能. 良好的电化学性能归因于这种独特的碳纳米管原位封装Ni₃S₂纳米颗粒结构. 碳纳米管不但可以提高复合材料的导电性,也可以缓冲Ni₃S₂纳米颗粒在反复充放电过程中产生的体积膨胀效应,明显改善了Ni₃S₂@CNT负极复合材料的电化学性能.     

Sn-Cl共掺杂的锂离子正极材料Li2MnO3的结构及电化学性能研究

以乙酸盐为原料,柠檬酸为络合剂,通过溶胶-凝胶的方法制备富锂阴极材料Li₂MnO₃,选用草酸亚锡(SnC₂O₄)为锡源,用Sn ⁴⁺代替Mn ⁴⁺,获得不同掺杂量的材料. 适当含量的Sn ⁴⁺掺杂可以提高材料的放电比容量,在低电流下获得256.3 mAh·g ^-1的高放电比容量,但由于Sn ⁴⁺离子半径过大,不能起到稳定结构的作用,材料的倍率性能较差. 在此基础上,选用氯化亚锡(SnCl₂)进行掺杂改性,在材料中同时引入Sn ⁴⁺和Cl ^-掺杂,获得了层状结构更完整的粉末样品. 通过共掺杂改性的阴极材料可以在20 mA·g ^-1的电流密度,经过80圈的循环仍然保持153 mAh·g ^-1的放电比容量,且此时还未出现衰减现象,库仑效率保持在96%以上;在400 mA·g ^-1的电流密度下提供的比容量可高达116 mAh·g ^-1,是未掺杂样品的2倍左右.     

三维网状结构Ru/石墨烯/碳纳米管复合材料作为锂氧电池正极催化剂的性能

利用物理浸渍和冷冻干燥等方法制备了具有三维网状结构的Ru/石墨烯/碳纳米管复合材料, 对该材料的结构、 形貌及电化学性能进行了表征和研究. 结果表明, 当Ru含量为30%, 热处理温度为500 ℃时, 材料的催化性能最优. 将其用作锂氧电池的正极催化剂, 以50 mA/g电流密度进行首次充放电时, 放电比容量约为5800 mA·h/g, 且在放电比容量为4000 mA·h/g以内时, 其极化电压仅为0.9 V; 当以50 mA/g电流密度进行恒容(500 mA·h/g)充放电循环时, 在极化电压低于1.1 V时, 仍能稳定循环12周. 复合材料电催化机理的研究结果表明, 三维网状结构不仅提供了O₂和Li⁺的传输通道, 更增加了放电产物Li₂O₂的储存场所. 金属钌纳米粒子的负载既增加了复合材料的反应活性位点, 又促进了放电产物Li₂O₂的分解.     

LiV3O8在Li2SO4水溶液中的电化学性能

采用低温固相法合成了具有纳米结构的LiV₃O₈材料.扫描电子显微镜（SEM）及透射电子显微镜（TEM）测试显示该材料具有纳米结构.X射线衍射（XRD）表明该材料属于单斜晶系,P2₁Im空间群.并采用循环伏安法（CV）及电化学阻抗谱图测试对该材料在1、2 mol·L^-1Li₂SO₄水溶液及饱和Li₂SO₄水溶液中的电化学行为进行了研究.结果表明,LiV₃O₈在饱和Li₂SO₄水溶液中具有最好的电化学性能.以LiV₃O₈作为负极材料,LiNi_1/3Co_1/3Mn_1/3O₂作为正极材料,饱和Li₂SO₄水溶液作为电解液组成了水性锂离子电池,进行恒流充放电测试,结果表明,在0.5C(1C=300 mA·g^-1)的充放电倍率下,该水性锂离子电池的首次放电比容量为95.2 mAh·g^-1,循环100次后仍具有37.0 mAh·g^-1的放电比容量.     

Na+掺杂锂离子电池正极材料LiNi0.6 Co0.2 Mn0.2 O2的制备及电化学性能

采用草酸盐共沉淀法制备了钠掺杂改性的Li_0.98Na_0.02Ni_0.6Co_0.2Mn_0.2O₂正极材料,借助X射线衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、能量分散谱（EDS）、感应耦合等离子体原子发射光谱（ICP-AES）、电化学阻抗谱（EIS）和恒电流充放电测试等手段对材料的颗粒形貌、晶体结构和电化学性能进行了研究.结果表明,掺钠后的材料具有更完善的α-NaFeO₂结构（空间群为+/Ni²⁺阳离子混排和更大的Li层间距,易于Li⁺在晶格中的快速脱嵌迁移.电化学性能测试结果证实掺钠样品具有优异的循环稳定性和高倍率性能,在2.7~4.3 V,1C下循环100次后,放电比容量仍为146 mA·h/g（容量保持率为95.4%）,在0.1C,0.2C,0.5C,1C,3C,5C,10C和20C时的放电比容量分别为181,168,162,155,143,136,126和113 mA·h/g.     

Na2PO3F对LiNi0.83Co0.11Mn0.06O2材料的复合改性及机理分析

采用湿化学法使用Na₂PO₃F对LiNi_0.83Co_0.11Mn_0.06O₂进行表面改性, 得到F^–掺杂和LiF包覆的正极材料. X射线衍射谱(XRD)结果显示(003)衍射峰向高角度偏移, 结合X射线光电子能谱(XPS)及透射电子显微镜(TEM)证明F^–进入到材料晶格内部; 扫描电镜(SEM)、TEM及XPS结果显示, 改性后材料表面存在均匀LiF包覆层, 可提高电极/电解液界面稳定性, 改善循环稳定性; 通过计算锂离子扩散系数, 证明Li⁺传输速率得到提升, 倍率性能改善. 电化学性能测试结果显示, 材料的循环稳定性和倍率性能均得到显著提高: 在2.75~4.3 V电压窗口下, 材料1 C循环200周后容量保持率由32.2%提高到65.2%, 10 C条件下放电比容量由145.7 mAh/g提高到161.5 mAh/g. 对循环后极片进行XPS分析, 正极-电解质界面(CEI层)层中的LiF, Li_xPO_yF_z, NiF₂减少, 有利于提高材料稳定性及循环性能.     

C/VN正极材料制备及其锂硫电池性能研究

制备了一种核壳带状C/VN复合材料,通过SEM和TEM研究了复合材料的形貌结构。以ZIF-8/V₂O₅·nH₂O、C/V₂O₅和C/VN三种材料作为含硫正极,锂片为负极,1.0 M LiTFSI,2%LiNO₃/DME∶DOL(体积比1∶1)为电解液,组装锂硫电池进行电化学测试。结果表明：C/VN能够显著提高正极材料的电化学性能,促进充放电过程中的电子转移;S@C/VN在0.5 C的电流密度下初始比容量为900.4 mAh/g,经过500圈后,仍能提供413.9 mAh/g的比容量,展现了S@C/VN优异的循环性能。     

亚微米去顶角八面体LiNi0.08Mn1.92O4正极材料制备及高温电化学性能

采用低温固相燃烧法快速制备了一种具有{111}、{110}和{100}晶面的去顶角八面体LiNi_0.08Mn_1.92O₄ (LNMO)正极材料, 其高暴露{111}晶面可以减少充放电过程中Mn的溶解, 面积相对较小的{110}和{100}晶面可增加Li⁺快速扩散的通道. 测试结果表明, 所合成的LNMO具有LiMn₂O₄特有的立方晶系结构, 其颗粒尺寸为亚微米级. LNMO的高温电化学性能优异, 在55 ℃, 1和5 C的首次放电比容量分别为109.9和98.0 mAh/g, 分别循环300次后容量保持率为75.8%和80.5%; 即使在55 ℃, 10和15 C下分别循环1000次后仍具有48.4%和49.4%的容量保持率, 而未掺杂的LiMn₂O₄于15 C循环1000次后容量损失高达98%. LNMO在55 ℃有较高的Li⁺扩散系数(D=3.86×10^-15 cm²/s)和较小的电荷转移阻抗(循环前、后R_ct=158.0和279.8 Ω)以及较低的表观活化能(E_a=17.63 kJ/mol), 说明Ni掺杂能够提高Li⁺在尖晶石型LiMn₂O₄内的扩散速率及减小锂离子在脱嵌过程中的能垒, 从而提高锂离子的扩散速率和倍率性能. 对LNMO于55 ℃循环1000次后的极片进行X射线衍射(XRD)分析, 发现LNMO电极材料的晶体结构基本保持不变, 表明Ni掺杂提高了锰酸锂材料在55 ℃长循环过程中的晶体结构稳定性, 有效抑制了Jahn-Teller效应及Mn的溶解, 显著提升了其高温电化学性能. 本工作为尖晶石LiMn₂O₄电极材料在高温方面的应用提供了借鉴.     

层状锰酸锂衍生物的阳离子价态与锂电池的电化学性能研究

采用溶胶-凝胶法, 通过锂盐、镍盐、钴盐与锰盐生成锂镍钴锰氧化合物的前驱体, 随后采用高温固相法合成了Li(Mn_1/3Co_1/3Ni_1/3)O₂. 借助于X射线光电子能谱(XPS)、X射线衍射(XRD)、循环伏安(CV)及充放电测试等现代测试手段研究了材料的晶型结构、离子价态及电化学性能. 前驱体经950 ℃煅烧可获得晶体结构完整、晶胞参数为a＝0.2864 nm, c＝1.4235 nm的六方层状Li(Mn_1/3Co_1/3Ni_1/3)O₂化合物; XPS结果表明Li(Mn_1/3Co_1/3Ni_1/3)O₂化合物表面上的Mn, Ni和Co分别以Mn^4＋, Ni^2＋和Co^3＋存在; 材料的高温放电比容量比室温要高, 在55 ℃下, 在2.5～4.6 V电压范围内, 电流密度为28 mA/g时材料首次放电容量195 mAh/g, 循环10次后容量保持在170 mAh/g; 循环伏安曲线上3.7 V和4.4 V的氧化还原过程对应于Ni^2＋/4＋和Co^3＋/4＋氧化还原电对的反应.     

Gels from a semifluorinated n-alkane in fluorinated solvents as a probe for intermolecular interactions

Diblock semifluorinated n-alkanes can form aggregates and gels in fluorinated solvents. We have investigated the thermal behavior of binary mixtures comprising F(CF₂)₈(CH₂)₁₆H and fluorinated solvents. The solvents were perfluorohexane, perfluoroheptane, perfluorooctane, perfluorooctyl bromide, perfluorodecalin, and perfluorotributylamine. The phase diagrams were used to calculate the activity coefficients of the two components and the main excess thermodynamic functions. The solubility and self-assembly behavior of F₈H₁₆ in the fluorinated solvents are related to the different solute–solvent dispersion interactions that depend on the polarizabilities and ionization potentials of the interacting species, and on the structural properties of the solvent.     

PMDA-BPDA-HAB聚苯并噁唑的合成及耐热性

PMDA-BPDA-HAB聚苯并噁唑的合成及耐热性;均苯四甲酸二酐;联苯四羧酸二酐;二羟基联苯胺;聚酰亚胺;聚苯并噁唑;耐热性     

HCOO在Cu(110)、Ag(110)和Au(110)表面的吸附

采用密度泛函理论(DFT)以及广义梯度近似方法(GGA)计算了甲酸根(HCOO)在Cu(110)、Ag(110)和Au(110)表面的吸附. 计算结果表明, 短桥位是最稳定的吸附位置, 计算的几何参数与以前的实验和计算结果吻合. 吸附热顺序为Cu(110)(-116 kJ·mol-1)>Ag(110)(-57 kJ·mol-1)>Au(110)(-27 kJ·mol-1), 与实验上甲酸根的分解温度相一致. 电子态密度分析表明, 吸附热顺序可以用吸附分子与金属d-带之间的Pauli 排斥来关联, 即排斥作用越大, 吸附越弱. 另外还从计算的吸附热数据以及实验上HCOO的分解温度估算了反应CO2+1/2H2→HCOO的活化能, 其大小顺序为Au(110)>Ag(110)>Cu(110).     

Transition metal complexes of the tripodal ligand 4-(2′-pyridylmethyl)-4-azaheptane-1,7-diamine. Crystal structures of [CuLCl]ClO4 and [NiL(MeCN)2](ClO4)2

The tripodal ligand 4-(2′-pyridylmthyl)-4-azaheptane-1,7-diamine has been prepared by reaction of 2-aminemethyl pyridine with acrylonitrile, followed by the reduction of the nitrile groups. Copper(II), nickel(II), zinc(II), cobalt(III) and chromium(III) complexes of the ligand have been prepared and characterized and the crystal structures of the complexes [CuLCl]ClO₄ and [NiL(MeCN)₂](ClO₄)₂ determined. The copper complex is five coordinate with approximate square pyramidal stereochemistry with the apical position occupied by a primary amine donor. The nickel complex is octahedral with the pyridine nitrogen donor lying trans to an acetonitrile ligand.     

SYNTHESIS AND CHARACTERIZATION OF METAL COMPLEXES WITH AMPICILLIN

Abstract

The reaction, in water, of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) ions with sodium ampicillinate at room temperature has allowed isolation of dimers with the following general formula [M(amp)Cl]₂ × nH₂O (n = 1.5?3.2). The complexes were characterized by elemental analyses, conductivity measurements, magnetic susceptibilities and spectroscopic methods (IR, Raman, EPR and UV-Visible). A dinuclear structure based on octahedrally coordinated metal ions is proposed.     

Magnetism of metal-nitroxide compounds involving bis-chelating imidazole and benzimidazole substituted nitronyl nitroxide free radicals

Coordination compounds based on imidazole and benzimidazole substituted nitronyl nitroxide radicals with transition metal ions and trivalent lanthanide ions are described from the perspective of their magnetic properties.For the transition metal compounds the crystal structures show various metal-nitroxide dimensionalities including mononuclear (0D), one-dimensional (1D) and two-dimensional (2D) complexes. The mononuclear complexes were isolated with most metal ions of the first transition series. One copper(II) complex shows a copper(II)-radical ferromagnetic coupling (J = +75 cm⁻¹) while for the other mononuclear compounds, mainly with manganese(II), the metal-radical interactions are antiferromagnetic. The one-dimensional and two-dimensional complexes are manganese(II) compounds which show canting effects leading to weak ferromagnetism.For the trivalent lanthanide ions [La(III), Gd(III) and Eu(III)], three series of mononuclear complexes were obtained in which the metal center is bound to four, two or one nitroxide radicals depending on the counter ions and ancillary ligands. Unexpectedly, in most gadolinium(III) complexes, the Gd(III)-radical interactions were found to be antiferromagnetic in contradiction with other foundings and previous theoretical models. In support to the magnetic studies, the optical properties of the lantanide complexes have also been investigated and are briefly described.     

New Complexes of Ditopic Ligands with “d” and/or “s” Metal Ions

Abstract

The asymmetric compartmental macrocycles containing one N₂O₂ or N₃O₂ Schiff base and one O₂O₃ or O₂O₄ crown-ether like chamber, have been obtained by condensation reaction of the formyl precursors 3,3′-(3-oxapentane-1, 5-diyldioxy) bis (2-hydroxybenzaldehyde) or 3,3′-(3,6-dioxaoctane-1,8-diyldioxy)-bis(2-hydroxybenzaldehyde) with ethyl ethylenediamine (H₂L_A, H₂L_C), 1,5-diamino-3-azamethylpentane(H₂L_B, H₂L_D), also in the presence of metal ions as templating agents. These ditopic ligands, with dissimilar coordination sites, have been designed and used for the selective complexation of “d” and/or “s” metal ions, respectively into the Schiff base and the crown ether chamber. The selectivity of these processes strongly depends on the size and on the donor atom sets of the sites. The possibility to obtain mononuclear M(L)·nH₂O (M = Ni²⁺, Cu²⁺, Co²⁺), Mn(L)(CH₃COO)·nH₂O or Na(L) and hetero-dinuclear MNa(L)(CH₃COO) (M = Ni²⁺, Cu²⁺, Co²⁺) and MnNa(L)(CH₃COO)₂·nH₂O complexes has been successfully tested. The ligands and complexes have been characterized by ir, nmr, mass spectrometry and magnetic susceptibility measurements.

Two of the ligands used for the preparation of the solid samples, i.e., to H₂L_A and H₂L_B, have been employed to study complexation reactions of Co(II) and Na(I) in solution. In order to obtain information on the ligand preorganization effect toward the complex stabilities, a simpler open chain parent compound of H₂L_B (H₂L_E) has been also prepared and studied. FT-IR spectra show that H₂L_A is unable to complex Na⁺ in DMSO while the complexation reactions of Na⁺ by H₂L_B and of Co²⁺ by H₂L_A take place with slow kinetics. Therefore, thermodynamic data have been obtained only for the systems Co²⁺/H₂L_B and Co²⁺/H₂L_E. The thermodynamic parameters obtained for the complexation reactions show that the pre-organization of the donor atoms in H₂L_B does not add a significant contribution to the stabilities of the complexes. Both H₂L_B and H₂L_E form in DMSO 1:1, 1:2 and 1:3 = M:L complexes with very similar stabilities and almost equal enthalpies of formation. Physico-chemical studies suggest besides that the slow reaction of Na⁺ with H₂L_B is probably due to the formation of a 1:1 complex where the metal cation, initially occupying the O₃ cage of the ligand, slowly binds also the oxygens of the phenolic moieties. Spectral and calorimetric data on solutions containing H₂L_B and different Co²⁺: Na⁺ ratios evidence that in DMSO no stable heterodinuclear complexes form when the neutral ligand is considered.     

具有聚集诱导发光性质的近红外荧光染料

聚集诱导发光(AIE)现象的发现为解决传统有机荧光分子在高浓度和聚集形态下存在的荧光猝灭问题提供了最佳方案,并实现了在光电器件、化学传感、生物成像和靶向治疗等众多领域的广泛应用。随着对AIE发光机理研究的不断深入,AIE分子体系得到了极大的扩展。其中,一类具有给体-受体结构的AIE分子能够显著降低分子能隙,使发光分子波长从可见光区(400~700 nm)延伸到近红外(NIR)区(700~1700 nm)。由于NIR发光分子在生物医学领域中的独特优势,其已成为目前AIE研究的热点。随着对NIR分子设计及应用的不断探索,附加不同功能且发光波长更长的AIE分子也被开发出来了,并实现了对生物体特定组织的NIR荧光成像、光声成像、光动力治疗和光热治疗等。本文总结了近年来具有AIE性能的NIR荧光分子的结构及其在生物医学领域的相关应用。     

Simple,Selective, and Sensitive Spectrophotometric Method for Determination of Trace Amounts of Nickel（Ⅱ）, Copper （Ⅱ）, Cobalt （Ⅱ）, and Iron （Ⅲ） with a Novel Reagent 2-Pyridine Carboxaldehyde Isonicotinyl Hydrazone

A selective and sensitive reagent of 2-pyridine carboxaldehyde isonicotinyl hydrazone（2-PYAINH） was synthesized and studied for the spectrophotometric determination of nickel, copper, cobalt, and iron in detail. At a pH value of 7.0, 9,0, 9.0, and 8.0, respectively, which greatly increased the selectivity; nickel, copper, cobalt, and iron reacted with 2-PYAINH to form a 1：2 yellow-orange, 1：2 yellow-green, 1：2 yellow and 1：1 yellow complexes, with absorption peaks at 363, 352, 346, and 359 nm, respectively. Under the optimal conditions, Beer＇s law was obeyed over the ranges of 0.01-1.4, 0.01-1.5, 0.01-2.7, and 0.01-5.4 mg/L respectively. The apparent molar absorptivity and Sandell＇s sensitivities were 8.4×10^4, 5.2×10^4, 7.1×10^4, and 3.9×10^4 L·mol^-l·cm^-1, respectively, and 0.00069, 0.0012, 0.00078, and 0.0014 μg·cm2, respectively. The detection limits were found to be 0.001, 0.002, 0.003, and 0.01 mg/L, respectively. The detailed study of various interfering ions to make the method more sensitive was carried out and selective and several real samples were analyzed with satisfactory results.     

Spectrophotometric study of Cd(II), Pb(II), Hg(II) and Zn(II) complexes with 5,10,15,20-tetrakis(4-carboxylphenyl)porphyrin

The reaction of 5,10,15,20-tetrakis(4-carboxylphenyl)porphyrin (TCPP) with Cd(II), Pb(II), Hg(II) and Zn(II) was studied spectrophotometrically and kinetics, equilibrium constants as well as photodecomposition of complexes were determined. It was verified that these metal ions with large radius accelerate the incorporation reaction of zinc into TCPP. On the basis of the mechanism and kinetics of this reaction, a sensitive method for the spectrophotometric determination of trace amounts of Zn(II) has been developed. The molar absorptivity of examined Zn-TCPP complex and Sandell's sensitivity at 423 nm were 3.5×10⁵ M⁻¹ cm⁻¹ and 18.3 ng cm⁻². The detection limit for the recommended procedure was 1.4×10⁻⁹ M (0.9 ng ml⁻¹) and precision in range 20-100 ng ml⁻¹ not exceeds 2.7% RSD. The proposed method applied for zinc determination in natural waters and nutritional supplement was compared with AAS results and declared value.