钽离子掺杂对LiFePO4 / C物理和电化学性能的影响

采用PAM(聚丙烯酰胺)模板-溶胶凝胶法在惰性气氛下合成钽掺杂的LiFePO₄/C复合正极材料，考察了钽对目标化合物的物理和电化学性能的影响。研究结果表明，0.33C的电流下充放电时，掺杂前后第2个循环的放电容量分别为138.6 mAh·g^-1和155.5 mAh·g^-1，循环20次后容量为141 mAh·g^-1和156 mAh·g^-1。电化学交流阻抗表明，掺杂后的材料阻抗R_ct从180 Ω减小到120 Ω。振实密度比掺杂前提高0.312 g·cm^-3。     

类球形正交LiMnO2的制备、微结构和电化学性能

以共沉淀法得到的类球形MnCO₃为前驱物，制备了类球形正交LiMnO₂(So-LiMnO₂)，采用XRD、SEM和N₂吸附技术对样品进行表征；与非球形正交LiMnO₂(No-LiMnO₂)进行了对比研究。结果表明：o-LiMnO₂的堆垛层错度、结晶状况、颗粒形貌和大小与前驱物的微结构密切相关；在80次电化学循环测试过程中，So-LiMnO₂经15次循环可达最大的放电容量152 mAh·g^-1，其容量衰减平均每次循环0.58 mAh·g^-1；而No-LiMnO₂要经过38次循环才能达到最大放电容量128 mAh·g^-1，容量衰减平均每次循环高达1.24 mAh·g^-1。TEM和EDS分析证明：由一次粒子团聚的类球形So-LiMnO₂能有效地抑制电解液对材料的腐蚀、减少Mn的溶解，从而提高了电化学循环能力。     

负极材料NiO的制备及电化学性能

以Ni(NO₃)₂·6H₂O和NaOH为原料,采用水热法合成了锂离子电池负极材料NiO。通过TG-DSC分析，确定了合成过程的反应机理。通过XRD、SEM和恒流充放电测试,研究了NiO样品的结构、形貌及电化学性能。400 ℃焙烧得到立方结构的NiO产品，以0.10 mA·cm^-2充放电,首次放电比容量达到1 151 mAh·g^-1，经过20次循环后的比容量仍为776 mAh·g^-1。     

锂离子蓄电池正极材料LiMn2-x-y-zTlxAlyMzO4(M=Co、Cr、Ni)的合成及电化学性能研究

采用同时掺杂Tl、Al和M(M=Co、Cr和Ni)三种金属原子和改进固相反应的方法合成了复合尖晶石正极材料 LiMn_2-x-y-zTl_xAl_yM_zO₄，并采用XRD、SEM、TEM、循环伏安和电化学测试考察了它的物理性质和电化学性能。结果表明，所合成的正极材料具有与母体LiMn₂O₄尖晶石同样完整的尖晶石结构，规则的形貌和均匀的粒径分布。当M为Co和Cr时，目标材料的平均粒径约800nm，且具有良好的电化学性能，其首次充电容量分别为123.70mAh·g^-1和121.30mAh·g^-1，首次放电容量分别为117.30mAh·g^-1和115.70mAh·g^-1。当M为Ni时，材料的电化学性能相对较差。循环伏安和充放电曲线表明该正极材料的充放电分别为两步脱锂和插锂机理。当Li掺杂量较小时，目标材料在充放电过程中均各有两个平台。随着Li掺杂量的增加，充放电平台有由两个逐渐转变为一个的趋势。当M为Co或Cr时，该正极材料不仅拥有较高的比容量和常温循环稳定性能，而且还具有较优良的高温循环稳定性能，这可能主要归因于三种金属的协同作用使目标材料的结构更加稳定，这也使该材料有可能成为电动车电池的较佳正极材料。     

锂离子电池正极材料LiNi0.75-xCoxMn0.25O2的合成及电化学性能研究

以LiOH·H₂O、Ni(OAc)₂·4H₂O、Co(OAc)₂·4H₂O和MnO₂为原料，在水热反应釜中预处理，然后进行高温固相反应，合成了一系列锂镍钴锰氧化物LiNi_0.75-xCo_xMn_0.25O₂(x=0.05,0.10,0.15,0.20,0.25)。通过X射线衍射(XRD)、扫描电子显微镜（SEM）和电化学性能测试对所得样品的结构、形貌、粒径及电化学性能进行了表征。结果表明，当x=0.20时，所合成的正极材料具有很好的α-NaFeO₂型层状晶体结构，晶胞参数a=0.286 1 nm，c=1.416 4 nm， V=0.100 4 nm³，以50 mA·g^-1的电流密度在3～4.3 V(vs Li/Li⁺)充放电时，首次放电比容量达172.5 mAh·g^-1，首次放电效率高达90.9%，30个循环后其放电比容量依然保持在161.1 mAh·g^-1。     

离子电池正极材料LiNi0.5Mn0.5O2的合成

采用共沉淀法制备锂离子电池正极材料LiNi_0.5Mn_0.5O₂，前驱体制备过程中金属离子氢氧化物的形貌、粒径分布和最终合成材料的性能息息相关。本文讨论了共沉淀反应过程中沉淀体系、pH值、搅拌速度和氨水浓度对沉淀产物形貌的影响。同时还考察了烧结制度对材料电化学性能的影响。结果表明，在优化条件下制备的正极材料LiNi_0.5Mn_0.5O₂首次放电容量高达178 mAh·g^-1，50个循环后放电容量稳定保持在165 mAh·g^-1(电压范围2.8～4.5 V，电流密度30 mA·g^-1)。     

高温固相法合成LiNi1/3Mn1/3Co1/3O2及其性能研究

采用高温固相法合成出层状锂离子电池正极材料LiNi_1/3Mn_1/3Co_1/3O₂。通过XRD、ICP、SEM和电化学测试手段对产物的结构、组成、形貌及电化学性能进行了研究。XRD结果表明此方法合成的LiNi_1/3Mn_1/3Co_1/3O₂具有标准的α-NaFeO₂型层状结构，SEM照片显示颗粒粒径大约在500 nm左右，粒径分布较窄。以20 mA·g^-1电流密度放电，充放电电压在2.8～4.4 V之间，其首次放电比容量为170 mAh·g^-1，40次循环容量保持率为85.3%。进一步加入石墨导电剂后，同样条件下首次放电比容量变为179 mAh·g^-1，50次循环容量保持率为89.6%。容量衰减主要发生在前10次循环。XRD和SEM测试表明循环初期容量衰减的原因是由材料本体结构变化和界面反应共同作用的结果。     

微乳液法合成LiFePO4 / C正极材料及其电化学性能

本文采用微乳液方法合成了纳米LiFePO₄ / C正极材料。制备样品分别用XRD和SEM进行表征，充放电测试其电化学性能。600 ℃制备样品为单一物相，平均粒径90 nm，在室温2.0～4.0 V (vs Li) 放电电压范围和15 mA·g^-1放电速率下，首次放电容量达到159 mAh·g^-1。制备样品同样展现良好的循环性能。在15 mA·g^-1速率下40次循环后，制备样品放电容量仍保持首次放电容量的98.9%。优异的电化学性能得益于样品颗粒的纳米尺寸、均匀分布以及表面碳层包覆提高了活性材料的电子电导率。     

以微乳液法制备的锰源合成LiMn2O4

采用CTAB-C₈H₁₈-C₄H₉OH-H₂O微乳体系制备出MnCO₃，将其灼烧成Mn₂O₃之后，与Li₂CO₃混合，800 ℃高温焙烧，获得了颗粒大小为数百纳米，均匀分布的纯相尖晶石LiMn₂O₄。这一材料的电化学性能优秀，0.5C的电流在3～4.2 V之间充放电时，首次放电比容量为124 mAh·g^-1，经过110次循环，保留比容量118 mAh·g^-1，平均每次容量损失<0.05%。该材料的倍率性能尤为优异，10C放电的比容量在110 mAh·g^-1以上，功率约为0.2C时功率的45倍。     

层状LiCo1/3Ni1/3Mn1/3O2正极材料的合成及电化学性能研究

采用液相法在800 ℃空气中烧结20 h合成出层状LiCo_1/3Ni_1/3Mn_1/3O₂正极材料。通过XRD、IR、SEM、XPS和电化学性能测试考察了产物的组成、结构、形貌及电化学性能。结果表明，所合成的LiCo_1/3Ni_1/3Mn_1/3O₂为六方单相，层状结构发育完善；产物呈球形且粒度小，分布窄，平均粒径为0.3 μm。以1 mA·cm^-2的电流密度，在2.7～4.3 V区间进行充放电测试，前4周的充放电比容量分别为168/160 mAh·g^-1、169/162 mAh·g^-1、165/160 mAh·g^-1、163/158 mAh·g^-1，循环性能优良。循环伏安实验表明，该材料在3.9 V附近出现了一对对称性好的氧化还原峰。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.