LaF3表面修饰LiMn2O4的合成方法及电化学性能的研究

通过高温固相法制得尖晶石LiMn₂O₄,然后在通过简单易行的无水乙醇蒸干法包覆LaF₃来修饰LiMn₂O₄。利用XRD,SEM来表征LaF₃修饰的LiMn₂O₄的结构和形貌特征,并通过电化学测试研究LaF₃修饰LiMn₂O₄的高温和常温下的电化学性能,另外结合电化学阻抗谱（EIS）和循环伏安（CV）考察表面修饰的锰酸锂的循环阻抗和循环可逆性。结果显示：经LaF₃修饰过的LiMn₂O₄仍具有尖晶石结构,并且具有良好的电学性能。其中,以3wt%的修饰效果最好,常温循环100次和高温循环50次的循环保持率分别是91%和90%;而且,EIS和CV分别表明经LaF₃修饰的LiMn₂O₄的电荷传递阻抗明显减小,其循环可逆性也明显提高。     

Zr掺杂对正极材料Li(Ni0.9Co0.05Al0.05)O2的电化学性能影响

通过控制结晶法制备类球形Ni_0.9Co_0.05Al_0.03Zr_0.02（OH）₂前驱体,与LiOH·H₂O均匀混合后,在750℃下于氧气中进行高温焙烧,最终合成正极材料Li（Ni_0.9Co_0.05Al_0.03Zr_0.02）O₂。扫描电子显微镜（SEM）结果显示前驱体及正极材料具有良好的形貌;X射线衍射（XRD）表明材料具有规整的六方单相层状α-NaFeO₂结构;能谱仪（EDXS）分析表明Zr元素在材料颗粒内部呈均匀分布。合成的LiNi_0.9Co_0.05Al_0.03Zr_0.02O₂正极材料具有良好的电化学性能,在25℃,2.8~4.3 V充放电条件下,0.2C首次放电比容量为221.5 mAh·g^-1,充放电效率90.3%,2C倍率充放电条件下容量仍达到192.7 mAh·g^-1,100周循环后的容量保持率为92.2%。在55℃,2.8~4.3 V的高温充放电条件下,该材料的0.2C首次放电比容量可达236.2 mAh·g^-1,2C充放电倍率下循环100周容量保持率为85.1%。     

固相反应法制备α-LiAlO2包覆LiNi0.4Co0.2Mn0.4O2的电化学性能研究

以提高锂离子电池正极材料LiNi_0.4Co_0.2Mn_0.4O₂的循环性能为目的,以LiNO₃和Al(OH)₃为原料,采用固相反应法制备了α-LiAlO₂包覆LiNi_0.4Co_0.2Mn_0.4O₂正极材料。微观组织结构分析结果表明,包覆热处理后LiNi_0.4Co_0.2Mn_0.4O₂颗粒表面形成了一层不均匀絮状包覆物α-LiAlO₂。电化学测试表明,α-LiAlO₂包覆处理有效减缓了充放电循环过程中总阻抗的增加,改善了材料的循环性能。3wt% LiAlO₂包覆的正极材料在室温1C充放电循环100次后,平均每次衰减率由包覆前的0.19%下降到0.14%。     

锂离子电池正极材料LiNi0.5Co0.4Al0.1O2的合成与性能

采用高温固相法制备了锂离子电池正极材料LiNi_0.5Co_0.4Al_0.1O₂。采用X射线衍射(XRD)、傅里叶红外光谱(FTIR)、扫描电子显微镜(SEM)对材料的结构及表观形貌进行分析。通过恒电流充放电以及循环伏安法进行了电化学性能测试。测试结果表明,充放电电压在3~4.5 V之间,在0.2C倍率下首次放电比容量达到159.9 mAh·g^-1,经50次循环充放电后放电容量为142.6 mAh·g^-1,表现出良好的电化学性能。     

锂离子电池正极材料LiNi0.5Co0.4Al0.1O2的合成与性能

采用高温固相法制备了锂离子电池正极材料LiNi_0.5Co_0.4Al_0.1O₂,采用X射线衍射(XRD)、傅里叶红外光谱(FTIR)、扫描电子显微镜(SEM)对材料的结构及表观形貌进行分析。通过恒电流充放电以及循环伏安法进行了电化学性能测试。测试结果表明,充放电电压在3~4.5V之间,在0.2C倍率下首次放电比容量达到159.9mAh·g^-1,经50次循环充放电后放电容量为142.6mAh·g^-1,表现出良好的电化学性能。     

Li3V2(PO4)3的溶胶-凝胶合成及其性能研究

以LiOH·H₂O(LiF、Li₂CO₃、LiCH₃COO·2H₂O)、NH₄VO₃、H₃PO₄和柠檬酸为原料,采用Sol-gel法合成锂离子电池正极材料Li₃V₂(PO₄)₃。优化了锂源、溶胶的pH值、预烧条件、煅烧温度等合成条件,并采用XRD、SEM、恒电流充放电及循环伏安试验等方法,研究了所合成的Li₃V₂(PO₄)₃的结构形貌和电化学性能。结果表明,以LiOH·H₂O为锂源,溶胶的pH值等于3,于氩气氢气(体积比9∶1)混合气中300 ℃预烧 4 h,并在氩气氢气(体积比9∶1)混合气中600 ℃煅烧8 h合成的Li₃V₂(PO₄)₃正极材料为标准的单斜结构,具有较高的放电比容量和较好的循环稳定性,0.1C和1C倍率下首次放电比容量分别为130 mAh·g^-1和129 mAh·g^-1;1C倍率下循环40次后,容量仍为127 mAh·g^-1,容量保持率为98.4%;随后又进行10C倍率放电,10次循环后容量为105 mAh·g^-1,容量保有率达98.1%。循环伏安测试表明,该正极材料具有较好的电化学可逆性。     

锰源对尖晶石LiMn2O4高温性能的影响

为考察不同锰源对所制备尖晶石LiMn₂O₄(LMO)电化学性能的影响(特别是高温性能),采用沉淀法制备前驱体,通过不同煅烧温度制备得到最常用的锰氧化物(MnO₂、Mn₂O₃和Mn₃O₄)为锰源,经相同条件制备得到LMO正极材料,通过考察所得LMO形貌及电化学性能来研究锰源与LMO电化学性能的关系。研究结果表明,相同的前驱体在不同煅烧温度下可以得到不同的锰氧化物,且各自具有不同的形貌结构。由这些锰氧化物都可以得到高纯度的LMO,但产物形貌结构以及材料中的八面体晶体含量和尺寸不同。由Mn₂O₃制备得到的LMO材料中的八面体晶体含量最多,且尺寸最均匀,在3种LMO中容量性能、倍率性能和循环性能最好：0.2C(1C=148 mA·g^-1)下首次放电比容量为131.8 mAh·g^-1;3C下还有100.4 mAh·g^-1的放电比容量。其对应半电池在0.5C下循环100次后,放电比容量还有116.0 mAh·g^-1,容量保持率为93.9%,电化学储能性能远远优于其他2种LMO。即使是在高温55 ℃下,由Mn₂O₃得到的LMO也表现出明显优于其他2种材料的高倍率性能和抗衰减性能。     

导电氧化物AZO对尖晶石型LiMn2O4高温性能的改善及研究

采用溶胶凝胶法对尖晶石型LiMn₂O₄正极材料进行铝掺杂氧化锌(AZO)包覆改性,并通过XRD、SEM、EDS、TEM、EIS、ICP -AES和充放电测试等手段对其结构,形貌及电化学性能进行表征。研究结果表明,AZO包覆层有效的阻止了LiMn₂O₄颗粒和电解液的直接接触,抑制了高温下锰溶解,明显改善了LiMn₂O₄的高温循环性能。1.5wt% AZO包覆的LiMn₂O₄正极材料在高温(55℃)1C时,首次放电比容量为114 mAh·g^-1,经过100次循环后,容量保持率仍高达95.4%,远高于未包覆LiMn₂O₄的70.6%。此外,1.5wt% AZO包覆的LiMn₂O₄表现出了优越的大倍率放电性能,在10C下放电比容量能达到99 mAh·g^-1。     

层状Li(Ni1/3Co1/3Mn1/3)O2正极材料的合成与电化学性能研究

采用共沉淀-喷雾造粒法制备前驱体, 于750 ℃在空气中煅烧20 h合成出层状Li(Ni_1/3Co_1/3Mn_1/3)O₂正极材料, 并用XRD, SEM, 粒度分析和电性能测试考察了所得材料结构、形貌及电化学性能. 本层状Li(Ni_1/3Co_1/3Mn_1/3)O₂正极材料具有α-NaFeO₂结构, 六方晶系, R3m空间群, 其晶胞参数为a＝0.2865 nm, c＝1.4238 nm. 当材料分别在2.8～4.2, 2.8～4.5 V间进行充放电时, 其首次放电容量分别为173.5和185.4 mAh•g^－1, 首次充放电效率分别为90%和83.8%, 40次循环后容量保持率分别为96%和84%.     

尖晶石型LiMn2O4的制备及超级电容性能研究

采用高温固相法制备LiMn₂O₄。X射线衍射结果表明800 ℃下得到尖晶石型LiMn₂O₄。利用恒流充放电、循环伏安和交流阻抗等研究了LiMn₂O₄电极材料在2 mol·L^-1 (NH₄)₂SO₄溶液中的超级电容性能。循环伏安测试结果表明LiMn₂O₄电极材料在0～1 V电位窗口范围内具有较好的方形特征；恒流充放电结果表明充放电曲线呈现出较规整的三角形对称分布，放电曲线呈直线关系，5 mA·cm^-2下的放电比容量为141 F·g^-1，具有较高的充放电效率，循环性能稳定；交流阻抗结果也显示LiMn₂O₄电极材料在2 mol·L^-1 (NH₄)₂SO₄中具有典型的电容阻抗特性。     

Charge ordering and dielectric properties in the near half-doped Pr0.79Na0.21MnO3 perovskite

The Pr_0.79Na_0.21MnO₃ perovskite has been prepared in polycrystalline form by a ceramic method. We have carried out its structural characterization by synchrotron X-ray powder diffraction (SXRPD) at room temperature and at 150 K (T<T_CO). In the charge ordering (CO) state, the SXRPD data can be refined both on the basis of the site-centred model and the bond-centred model proposed for half-doped manganites, without a clear advantage of one model over the other. From the dielectric point of view, at the CO temperature this manganite shows a maximum in the dielectric constant whose origin is intrinsic, and cannot be attributed to the presence of extrinsic factors. We relate this dielectric behaviour to the formation of polar entities at the temperature of charge condensation, due to an asymmetric charge distribution intermediate between site-centred and bond-centred type.     

Complexes of neodymium and dysprosium triiodides with amines. Molecular structures of the {Dy[Me2N(CH2)3NH2]8}I3, NdI3(PriNH2)4, and NdI3(PriNH2)5 complexes

The dissolution of DyI₂ in diamine Me₂N(CH₂)₃NH₂ (DMDA) is accompanied by the disproportionation of the salt, hydrogen evolution, and oxidation of Dy^II to Dy^III. The [Dy(DMDA)₈]I₃ complex (1) was isolated from the solution. The neodymium amide amine complex (PrⁱNH)NdI₂(IPA)₄ was produced by the reaction of NdI₂ with isopropylamine (IPA). The recrystallization of this complex from IPA afforded the NdI₃(IPA)₄ complex (2). The recrystallization of (PrⁱNH)NdI₂(IPA)₄ from a toluene-IPA mixture gave the complex with five amine ligands, NdI₃(IPA)₅ (3). The structures of compounds 1, 2, and 3 were established by X-ray diffraction. Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1674–1679, September, 2007.     

Complex salts (DienH3)[IrCl6](NO3), (DienH3)[PtCl6](NO3), and (DienH3)[IrCl6]0.5[PtCl6]0.5(NO3): Synthesis, structure, and thermal properties

The complex salts ((DienH₃)[IrCl₆](NO₃) (I), (DienH₃)[PtCl₆](NO₃) (II), and (DienH₃)[IrCl₆]_0.5[PtCl₆]_0.5(NO₃) (III) (where Dien is NH₂(CH₂)₂NH(CH₂)₂NH₂) were synthesized and characterized by elemental, X-ray diffraction, and thermal analyses and by electronic and IR spectroscopies. Solid solution of the composition Ir_0.35Pt_0.65 was obtained by decomposition of compound III in the atmosphere of hydrogen. Original Russian Text ? E.V. Makotchenko, I.A. Baidina, P.E. Plusnin, L.A. Sheludyakova, Yu.V. Shubin, S.V. Korenev, 2007, published in Koordinatsionnaya Khimiya, 2007, Vol. 33, No. 1, pp. 47–54.     

Crystal and molecular structure of (NH4)2[UO2(NO3)4] and [(NH4)(18C6)]2[UO2(NO3)4]

Single crystals of diammonium tetranitratouranylate (NH₄)₂[UO₂(NO₃)₄] (I) and a new diammonium tetranitratouranylate complex with 18-crown-6 [(NH₄)(18C6)]₂[UO₂(NO₃)₄] (II) have been synthesized by the reaction of diaquadinitratouranyl tetrahydrate with ammonium nitrate in a nitric acid solution and the reaction of the same reagents with 18C6 in an ethanol solution, respectively. The X-ray diffraction analysis of compounds I and II has been performed. Crystals of compounds I and II are monoclinic, Z = 2, space group P2₁/n, a = 6.4075(5) ?, b = 7.7851(7) ?, c = 12.4461(12) ?, β = 101.239(1)°, V = 608. 94(9) ?³ for compound I and a = 10.542(9) ?, b = 8.590(8) ?, c = 22.5019(19) ?, β = 101.632(1)°, V = 2058.3(3) ?³ for compound II. The [UO₂(NO₃)₄]²⁻ complex anion in compounds I and II contains two monodentate and two bidentate cyclic nitrato groups, and the coordination number of uranyl is 6. The 18C6 molecule in the structure of compound II has the classic crown conformation and combined with the ammonium ion by three hydrogen bonds. Compounds I and II formed by electrostatic attraction forces between counterions are stabilized by (NH₄⁺)NH...O(NO₃⁻) interionic hydrogen bonds.     

Synthesis and characterization of the [Cu(Cin2bda)2]ClO4 and [Cu(Ncin2bda)2]ClO4 complexes: Crystal structure of [Cu(Ncin2bda)2]ClO4

Two copper(I) complexes [Cu(Cin₂bda)₂]ClO₄ (I) and [Cu(Ncin₂bda)₂]ClO₄ (II) have been prepared by the reaction of the ligands N²,N²′-bis(3-phenylallylidene)biphenyl-2,2′-diamine (L¹) and N²,N²′-bis[3-(2-nitrophenyl)allylidene]biphenyl-2,2′-diamine (L²) and copper(I) salt. These compounds were characterized by CHN analyses, ¹H NMR, IR, and UV-Vis spectroscopy. The C=N stretching frequency in the copper(I) complexes shows a shift to a lower frequency relative to the free ligand due to the coordination of the nitrogen atoms. The crystal and molecular structure of II was determined by X-ray single-crystal crystallography. The coordination polyhedron about the copper(I) center in the complex is best described as a distorted tetrahedron. A quasireversible redox behavior was observed for complexes I and II. The article is published in the original.     

Synthesis and structure of [Ph3MeP]3[Sb3I12]·Me2C=O, [Ph3MeP]3[Sb2I9], [Ph3MeP]2[SbI5], and [Ph3MeP]3[Sb3I12] antimony complexes

Complexes [Ph₃MeP]₃[Sb₃I₁₂]Me₂C=O (I), [Ph₃MeP]₃[Sb₂I₉] (II), and [Ph₃MeP]₂[SbI₅] (III) were obtained via the reaction of triphenylphosphonium iodide with antimony triiodide in acetone in 1:1, 3:2 and 2:1 molar ratios. Reaction of the complex III with antimony triiodide (1:1) affords [Ph₃MeP]₃[Sb₃I₁₂] (IV). The structure of the obtained complexes was confirmed by X-ray analysis.     

The evaluation of singlet-triplet separations for [W2(μ-H)(μ-Cl)Cl4(μ-dppm)2] and [W2(μ-H)2 (μ-O2CC6H5)2(P(C6H5)3)2] based on P NMR and crystallographic data

The singlet-triplet separations for the edge-sharing bioctahedral (ESBO) complex W₂(μ-H)(μ-Cl)(Cl₄(μ-dppm)₂ · (THF)₃ (II) has been studied by ³¹P NMR spectroscopy. The structural characterization of [W₂(μ-H)₂(μ-O₂CC₆H₅)₂Cl₂(P(C₆H₅)₃)₂] (I) by single-crystal X-ray crystallography has allowed the comparison of the energy of the HOMOLUMO separation determined using the Fenske-Hall method for a series of ESBO complexes with two hydride bridging atoms, two chloride bridging atoms and the mixed case with a chloride and hydride bridging atom. The complex representing the mixed case, [W₂(μ-H)(μ-Cl)Cl₄(μ-dppm)₂ · (THF)₃] (II), has been synthesized and the value of −2J determined from variable-temperature ³¹P NMR spectroscopy.     

Trimeric, Cyclic Dimethyltin-Containing Tungstophosphate [{(Sn(CH3)2)(Sn(CH3)2O)( A- PW9O34)}3]21?

The trimeric, cyclic dimethyltin-containing tungstophophate [{(Sn(CH₃)₂)(Sn(CH₃)₂O)(A-PW₉O₃₄)}₃]²¹⁻ (1) has been synthesized in aqueous acidic medium and characterized by IR, elemental analysis, electrochemistry, and FT-ICR MS. Single-crystal X-ray analysis was carried out on Cs₁₂Na₉[{(Sn(CH₃)₂)(Sn(CH₃)₂O)(A-PW₉O₃₄)}₃]·20H₂O (1a), which crystallizes in the trigonal system, space group R3, with a = b = 29.7445(7) ?, c = 15.5915(7) ? and Z = 3. Polyanion 1 is composed of three trilacunary (A-PW₉O₃₄) Keggin fragments that are linked on one side via three isolated dimethyltin groups and on the other side by a (Sn₃(CH₃)₆O₃) unit and three cesium ions, resulting in a cyclic assembly with C _3v symmetry. The discrete molecular, hybrid organic–inorganic 1 was synthesized by reaction of (CH₃)₂SnCl₂ with Na₉[A-PW₉O₃₄] in 0.5 M sodium acetate buffer (pH 4.8). Comparison of several characteristics of the cyclic voltammograms of 1 and (A-PW₉O₃₄)⁹⁻, including the potential location of their reduction peaks, the difference in their current intensities and their qualitative relative electron transfer speeds, supports the conclusion that the solid-state structure of 1 is retained in solution. The presence of (PW₉O₃₄)-based species in solutions of 1 was also confirmed by FT-ICR mass spectrometry. Dedicated to Professor Günter Schmid on the occasion of his 70th birthday.     

Polynuclear complexes of gold(III) of the composition ([Au(S2CNR2)2][AuCl4])n (R = C4H9, R2 = (CH2)5): Synthesis, supramolecular structures, and thermal behavior

The interaction of binuclear cadmium dialkyldithiocarbamates [Cd₂(S₂CNR₂)₄] with solutions of AuCl₃ in 2M HCl gives polynuclear gold(III) complexes ([Au(S₂CNR₂)₂][AuCl₄]) _n , where R = C₄H₉ (I) and R₂ = (CH₂)₅ (II). The structures of the synthesized compounds solved by X-ray diffraction analysis are char-acterized by a complicated organization at the supramolecular level. The structures are based on polymer chains (I) and layers (II) involving isomeric cations [Au(S₂CNR₂)₂]⁺ and anions [AuCl₄]⁻. The thermal behavior of the synthesized complexes is studied by simultaneous thermal analysis including thermogravimetry and differential scanning calorimetry. The final product of the thermal transformations of the studied complexes is shown to be reduced metallic gold.