锂离子电池正极材料层状LiMnO2的掺杂改性

层状LiMnO2具有成本低、无毒和比容量高等优点，是一种非常有发展前景的正极材料。本文介绍了近年来国内外层状LiMnO2的研究进展。主要阐述了层状LiMnO2的结构与性能的关系。结合笔者的工作，着重探讨了离子掺杂改性对层状LiMnO2的电化学性能的影响。最后，简要指明了层状LiMnO2将来的可能研究方向。     

层状LiMnO_2正极材料的研究进展

层状LiMnO2 化合物的研究是目前锂离子电池正极材料锂锰氧化物研究工作的新热点 ,本文综述了近年来国内外LiMnO2 化合物的研究进展 ,主要阐述了具有层状和扭曲层状结构的m LiMnO2和o LiMnO2 的结构、电性能、合成和改性方法等方面的研究状况 ,重点介绍了离子交换法合成层状LiMnO2 的原因和机理。探索新的合成方法和掺杂其它金属离子改性以提高循环性能是今后LiMnO2 的研究趋势。     

层状LiMnO2正极材料的研究进展

层状LiMnO2化合物的研究是目前锂离子电池正极材料锂锰氧化物研究工作的新热点，本文综述了近年来国内外LiMnO2化合物的研究进展，主要阐述了具有层状和扭曲层状结构的m-LiMnO2和o-LiMnO2的结构、电性能、合成和改性方法等方面的研究状况，重点介绍了离子交换法合成层状LiMnO2的原因和机理。探索新的合成方法和掺杂其它金属离子改性以提高循环性能是今后LiMnO2的研究趋势。     

S-M(M=Cu, Co, Ti)复合掺杂层状LiMnO2 的合成及其电化学性能

用水热法合成了锂离子电池正极材料正交结构LiMnO2材料, 并对其进行S2－、大尺寸阳离子(Cu2＋, Co3＋, Ti4＋)以及硫-金属离子复合掺杂改性. 用X射线衍射(XRD)、X光电子能谱分析(XPS)、透射电子显微镜(TEM)、恒电流充放电、交流阻抗谱(EIS)等测试技术进行表征. 实验结果表明: 当掺入离子的含量较低时, 得到的产物能保持完整的正交结构, 并表现出较好的电化学性能. S2－和非Jahn-Teller效应大尺寸阳离子的掺入使材料的循环稳定性能大幅度提高, 而这种提高是源于这些离子对LiMnO2结构的稳定作用. 电极材料Li1.02Mn0.988Ti0.012O1.989S0.011显示了最优的电化学性能, 在50 mA•g－1放电速率下, 其初始放电容量为142.6 mAh•g－1, 60次循环后放电容量为213.4 mAh•g－1. 硫-金属阳离子复合掺杂, 综合了大尺寸阳离子可以提高材料中Li＋的扩散能力和S2－掺杂抑制Jahn-Teller畸变两方面优势, 使层状结构LiMnO2正极材料既保持了较高的容量又获得良好的循环性能.     

聚阴离子掺杂LiMnO_(2-y)X_y(X=BF_4~-,SiO_3~(2-),MoO_4~(2-),PO_4~(3-),BO_3~(3-))材料的合成及其电化学性能

采用水热法合成了聚阴离子掺杂LiMnO2-yXy(X=BF4-,SiO32-,MoO42-,PO43-,BO33-,y=0.01、0.03、0.05)锂离子电池正极材料。通过X射线粉末衍射(XRD)、X光电子能谱(XPS)、扫描电镜(SEM)和恒电流充放实验,研究了不同掺杂离子和掺杂量对产物结构和电化学性能的影响。结果表明,少量聚阴离子的掺杂未改变正交LiMnO2的晶体类型,但增大了材料晶胞体积,改善了材料的电化学循环性能。电化学交流阻抗(EIS)测试结果表明,聚阴离子掺杂增大了材料电荷转移阻抗,但明显提高了材料中Li+的扩散能力。     

锂电池正极材料Li1.06Mn0.8Cr0.14O2的水热合成及其光谱研究

采用水热方法合成了掺铬锂锰氧化合物, X射线衍射和Raman光谱分析结果表明, 所得材料为具有NaFeO2结构的晶体. 由等离子发射光谱(CIP)确定其组分为Li1.06Mn0.8Cr0.14O2. X射线光电子能谱(XPS)研究结果表明, 与未掺杂的LiMnO2相比, 所得材料中Mn的平均价态增加, 这将抑制因Mn3+离子的存在而产生的Jahn-Teller畸变, 有利于提高材料的电化学循环性能.     

正极材料Li(Ni0.5Mn0.5)1-xMxO2 (M=Ti，Al；x=0，0.02)电化学行为的比较研究

0IntroductionMany efforts have been made to develop newmaterials as an alternative to LiCoO2due to the rela-tively high cost and toxicity of Co.Much attention hasbeen paid to layered structure cathode materials suchas LiMnO2and LiNiO2due to their lower co…     

层状LiMnO_2的溶胶凝胶法合成及其改性

采用溶胶凝胶法合成了锂离子电池正极材料层状锰酸锂(o-L iMnO2),并对其进行了N i2+掺杂改性研究,优化了层状L iMnO2的合成路径及制备条件.采用XRD、充放电实验和交流阻抗测试方法研究了N i2+的掺入对o-L iMnO2充放电容量的影响.结果表明N i2+的掺入明显提高了锰酸锂的放电比容量和循环性能,抑制了循环过程中电池阻抗的增加.     

构建2D-2D TiO2纳米片/层状WS2异质结用以增强可见光响应光催化活性

自Fujishima等首次报道以来, TiO_2作为一种重要的光催化剂引起了人们的广泛关注.迄今为止,研究人员已经开发出了各种形貌的具有不同晶型结构的TiO_2,并用于光催化降解有机污染物.然而, TiO_2的宽禁带(3.2 eV)使其难以被可见光激活,导致对太阳光的利用效率低下.而且,在光催化反应中,低的量子效率无法满足实际应用.因此,开发具有可见光响应的高催化活性的TiO_2基催化剂具有重要意义.集成复合材料、纳米材料和界面的优势构建纳米复合材料已成为提高TiO_2光催化活性的重要策略. WS_2具有典型的类石墨烯层状结构和窄的带隙(1.35 eV),且其导带高于TiO_2的导带,适合作为助催化剂修饰TiO_2,使其具备可见光响应光催化活性.本文采用一步水热法,以二维(2D)TiO_2纳米片作基质材料,直接在其表面原位生长WS_2层,制得了2D-2D TiO_2纳米片/层状WS_2(TNS/WS_2)异质结. XRD及Raman结果表明,层状WS_2与TiO_2纳米片紧密结合在一起,且两者之间形成了W=O键.TEM结果显示,层状WS_2以面-面堆叠方式均匀地包覆在TiO_2纳米片表面,包覆层数约为4层.光催化性能测试结果表明,可见光照射下, TNS/WS_2异质结对RhB的光催化降解能力高于原始TiO_2纳米片和层状WS_2,光催化活性得到明显增强.紫外可见光谱试验结果显示,层状WS_2的引入极大地增强了异质结的光吸收性能. PL光谱测试表明, TNS/WS_2异质结具有更高效的载流子分离效率.为了进一步证实是光吸收性能的提升还是载流子分离效率的增强对光催化性能提起其主要作用,本文还研究了3D-2D TiO_2空心微球/层状WS_2(THS/WS_2)复合材料.结果表明, TNS/WS_2异质结比THS/WS_2复合材料具有更高效的光生电子和空穴的分离能力.从而证明了TiO_2纳米片与层状WS_2之间完美的2D-2D纳米界面和紧密的界面结合,显著增加了载流子分离效率,因此光催化活性得到明显提高.为了研究TNS/WS_2异质结光催化剂的光催化机理,采用重铬酸钾、草酸铵、叔丁醇和对苯醌作自由基猝灭剂进行了自由基捕捉剂实验.结果表明,空穴在RhB降解过程中起主要作用,超氧自由基起次要作用.基于自由基猝灭实验结果和带隙结构分析,提出了TNS/WS_2异质结对RhB的光催化机理为双转移光催化机理.可见,界面异质结工程化可能是制备高效和环境稳定的光催化剂的新思路     

Ni-CH_3CH_2NH_2/H_(1.78)Sr_(0.78)Bi_(0.22)Nb_2O_7复合层状钙钛矿的合成及光催化分解水产氢性能(英文)

自从分解水产氢被首次报道以来,许多光催化剂被开发出来并用于光催化分解水产氢.然而,由于光生电子和空穴的复合率普遍较高,大部分的光催化剂分解水产氢效率都很低.因此,开发新型高效的光催化材料至关重要.具有(Bi_2O_2)~(2+)(A_(m-1)M_mO_(3m+1))~(2-)通式的Aurivillius相层状钙钛矿材料因具有独特的层状结构、元素可调性以及优异的电荷传输和分离能力而广泛应用于光催化分解水和去除有机污染物.此外,当该类层状钙钛矿被剥离成超薄纳米片时,其光催化性能进一步提高.为了进一步提高层状钙钛矿的载流子分离能力,将客体(如贵金属,半导体等)通过化学反应的途径插入到层状钙钛矿的层间区域,从而合成出复合层状钙钛矿被广泛发展和应用.然而,引入的客体主要是贵金属和半导体,这类客体的高成本和不均匀分布制约了其进一步的应用.由于廉价、无毒和稳定等优点,镍基材料如Ni,NiO,Ni_2O_3,NiS,NiS_2,Ni(OH)2和Ni(OH)x等被广泛用作增强电极材料的光电性能和催化剂的光催化分解水产氢性能的助催化剂.本文采用简单的原位化学反应法制备出镍基配合物Ni-CH_3CH_2NH_2(Ni-EA)插层的Ni-CH_3CH_2NH_2/H_(1.78)Sr_(0.78)Bi_(0.22)Nb_2O_7(Ni-EA/HSNNs)复合层状钙钛矿;然后采用X-射线衍射(XRD)、傅立叶变换红外光谱(FTIR)、X-射线光电子能谱(XPS)、紫外-可见漫反射光谱等手段对Ni-EA/HSNNs光催化剂进行了系统的研究.XRD结果表明,引入Ni~(2+)后,HSNNs层间距减小并且平行于钙钛矿层的晶面结晶度增强,证明HSNNs沿垂直于钙钛矿层的方向出现了层层组装.FTIR和XPS结果表明,引入的Ni~(2+)与HSNNs层间和表面的乙胺分子之间存在较强的相互作用,结合高分辨透射电镜图可知,Ni的存在形态可能为配合物Ni-EA.由此可见,当向HSNNs中引入Ni~(2+)时,Ni~(2+)和HSNNs层间和表面的乙胺分子反应生成带正电的配合物Ni-EA,由于Ni-EA与HSNNs的钙钛矿层带有异种电荷,两者之间存在较强的静电相互作用力,从而引起钙钛矿纳米片HSNNs的层层组装,最后形成Ni-EA/HSNNs复合层状钙钛矿.光催化分解水产氢性能测试结果表明,当引入0.5 wt%Ni时,复合层状钙钛矿表现出最优的光催化性能.与HSNNs(241.58μmol/h)相比,0.5%Ni-EA/HSNNs的光催化分解水产氢速率(372.67μmol/h)提高了0.54倍,表现出与0.5%Pt/HSNNs可比拟的光催化活性,可见,非贵金属Ni具有替代贵金属Pt的能力.进一步的研究表明,镍基配合物Ni-EA显著增强了催化剂的光生载流子的传输和分离能力,从而提高了其光催化分解水产氢性能.该文为光催化分解水产氢提供了一种简便的合成非贵金属配合物助催化剂的方法.     

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%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

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.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

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.     

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%).