锂离子电池高容量合金基含锂负极材料的研究进展

现有的以石墨为负极的锂离子电池能量密度逐渐接近其理论极限. 基于合金化反应机制的高容量含锂负极材料Li_xM_y(M为能够和锂发生合金化反应的元素)是一类新兴的负极材料, 具有数倍于石墨的储锂比容量, 且可以为电池提供活性锂源. 这些特性使其能够与高容量无锂正极材料(如S, O₂, FeF₃和V₂O₅等)相匹配, 构建下一代高比能锂离子电池新体系. 本文综述了近年来高容量合金基含锂负极材料(如Li_xSi, Li_xSn, Li₃P和Li_xAl基系列材料)的研究进展, 分析了所面临的挑战, 概述了材料的合成与电极的制备方法, 并介绍了它们在常规锂离子电池、 锂离子-硫电池及锂离子-空气电池等多个全电池体系中的应用实例, 提出并举证了其电化学性能优化与调控的策略, 最后展望了未来的研究方向.     

碳材料在钛酸锂负极材料中的应用

尖晶石型结构的钛酸锂由于具有极高的循环寿命和安全特性,被认为是目前最具应用前景的锂离子电池负极材料之一。但钛酸锂的电子电导率较低,且在充放电循环过程中易产生胀气问题,使其应用受到了极大的限制。将高导电、环境友好、化学和热性能稳定且结构多样的碳材料与钛酸锂形成复合负极材料,可有效提高材料的导电性,同时抑制胀气,对电极材料的性能优化起到非常关键的作用。本文综述了近年来碳材料在钛酸锂负极中的应用与研究进展,深入分析和探讨了碳材料对钛酸锂综合电化学性能的改善方式和改进效果,指出了不同形式的钛酸锂/碳复合材料在制备和应用中需要关注的问题,并对钛酸锂/碳复合材料未来可能的应用方向进行了展望。     

不同形貌结构Li4Ti5O12负极材料的最新进展

由于电子和信息行业的需要, 过去十年锂离子电池得以快速发展. 目前, 锂离子电池仍呈现需求量增长的趋势, 对锂离子电池的安全性要求也越来越高. 因此促使寻找一种比碳/石墨材料更安全, 循环性能更理想的锂离子电池负极材料以满足电动汽车等新兴行业的需求. 尖晶石型Li₄Ti₅O₁₂作为“零应变材料”具有优异的循环稳定性、价格便宜、容易制备、较高的平台电压和良好的安全性, 已成为锂离子动力电池负极材料的研究热点, 被认为是目前最具应用前景的锂离子电池负极材料. 由于形貌选择对于Li₄Ti₅O₁₂材料的电化学性能有着至关重要的影响, 本文综述了球形、多孔(中空)结构、纳微结构、核壳结构等不同形貌Li₄Ti₅O₁₂的合成及其性能研究的最新进展; 总结了各种形貌的优点, 已解决和待解决的问题, 常用合成方法以及各自的适应领域; 并对Li₄Ti₅O₁₂材料的发展趋势进行了展望.     

“锂硫电池”专辑序言

锂硫电池是指采用硫或含硫复合物作为正极，锂或含锂材料为负极，以硫-硫键的断裂/生成来实现电能与化学能相互转换的一类电池体系。由于活性物质具有质轻、多电子反应等特性，从而能够实现高达1675m Ah·g^-1的理论比容量和2600 Wh·kg^-1的质量比能量。这比传统的锂离子电池的能量密度高出7倍左右，极有潜力成为新一代高能量密度电化学储能体系，近年来一直是高能锂金属电池领域的研究热点之一。然而，锂硫电池的实用化依然存在着诸多问题。最为典型的是电池充放电过程中生成高阶态多硫化物(Li₂S_n,8≥n≥4)溶解在电解质中导致的“穿梭效应”，继而对硫基正极、锂基负极和电解液等电池关键组成部分产生深刻影响，导致电池出现容量衰减快、库仑效率低、循环寿命短等问题。其次，硫正极必须和金属Li配对使用才能体现锂硫电池高能量密度的优势。但在实际的锂硫电池中，锂基负极的充放电效率低、循环性能差，同时存在着严重的安全隐患。这些挑战仍需科研工作者对其背后的科学问题和工程技术问题进行逐一突破。     

有机碳源对LiTi2(PO4)3/C复合水系负极性能的影响

采用喷雾干燥与高温煅烧相结合的方法制备了球形LiTi₂(PO₄)₃/C复合水系负极材料, 探讨了基于不同包覆机制的有机碳源和碳包覆量对LiTi₂(PO₄)₃/C复合负极电化学性能的影响. 结果表明, 碳包覆量过低时不足以阻止水的侵蚀, 而碳含量过高时锂离子扩散的阻力过大, 磷酸钛锂电极最优碳包覆质量分数为13%. 碳包覆的均匀性和包覆层厚度是影响电极性能的两个重要因素. 基于原位聚合包覆机制的聚多巴胺包覆磷酸钛锂颗粒最均匀, 碳化后微晶结构较好, 具有良好的电子导电性, 以聚多巴胺为碳源制备的LiTi₂(PO₄)₃/C复合负极性能最优.     

基于钛酸锂负极和聚三苯胺正极的电池电容体系

由于高安全、高功率和超长循环寿命等优点,钛酸锂负极材料近年来得到了广泛关注,基于钛酸锂负极的高性能超级电池电容器和锂离子电池也成为近年来的研究热点. 本文采用化学氧化法制备了有机物正极材料聚三苯胺,并通过经典的电化学测试方法研究了其储能机理及相应的电极动力学过程. 研究结果表明,该有机物正极的储能机制主要是基于阴离子的吸脱附反应,并表现出85 mA·g^-1的可逆容量,且其动力学过程不受扩散控制,属于典型的赝电容行为. 将该正极与钛酸锂负极结合构成了新型的电池电容体系,并对其电化学性能进行了研究,结果表明该体系具有高功率特性,且能量密度高于传统的混合型超级电容器. 此外,本文还对该有机物正极的不足和实际应用中所面临的挑战做了初步分析.     

一种应用前景可观的新能源材料——尖晶石型Li4Ti5O12 *

各种锂离子电池电极材料作为十分重要的新能源材料近些年来受到前所未有的广泛关注。负极材料尖晶石型Li₄Ti₅O₁₂由于其特殊的“零应变”性等优良性质越来越多地受到研究者的青睐,成为一种应用前景可观的锂离子电池用负极材料。同时,其很多性能也很符合电动汽车用储能器件对电极材料的要求,也被研究用于新近提出的非对称超级电容器中。本文介绍了Li₄Ti₅O₁₂的结构和性能;从制备方法（溶胶-凝胶法、固相合成法等）、掺杂改性和与其他材料复合等几个方面介绍了国内外关于Li₄Ti₅O₁₂的制备和改性方面的研究进展;并对Li₄Ti₅O₁₂在各种器件中的应用研究进展做了介绍。     

新一代动力锂离子电池磷酸锰锂正极材料的研究现状与展望

磷酸锰锂（LiMnPO₄）正极材料具有能量密度高、成本低、安全性高和热稳定性好等优点,目前已成为锂电产业界研究的热点,有望成为继磷酸铁锂（LiFePO₄）之后的新一代正极材料. 然而,磷酸锰锂的电子电导率和锂离子扩散率均很低,其电化学性能提高较为困难,至今尚无法制备出满足实际应用的高性能LiMnPO₄正极材料,严重制约了LiMnPO₄材料及其电池的发展. 本文从LiMnPO₄的结构特性出发,对近年来国内外在碳包覆、离子掺杂、纳米化和控制晶体形貌等改性研究、全电池研究、专利情况以及商业化尝试等多方面进行了综述,并对LiMnPO₄的发展进行了展望.     

锂离子电池用富锂层状正极材料

正极材料与负极材料是锂离子电池重要组成部分。目前锂离子电池负极材料比容量通常在300mAh/g以上,而正极材料比容量始终徘徊在150mAh/g。正极材料正在成为锂离子电池性能进一步提升的瓶颈。富锂层状正极材料是一类新型正极材料,其可逆容量在200mAh/g以上,其高容量特性引起人们的广泛关注。这类材料可以用xLi₂MO₃·(1-x)LiM'O₂ (M 为Mn, Ti, Zr之一或任意组合; M'为Mn, Ni, Co之一或任意组合; 0≤x≤1)形式表示。由于其组成与结构的特殊性,这类富锂层状正极材料的充放电机理也不同于其它含锂过渡金属氧化物正极材料。本文介绍富锂层状正极材料的合成、结构与充放电机理,重点介绍近年来通过改性提高其电化学性能方面的研究进展,指出目前富锂材料研究中存在的问题,探讨未来的研究重点。     

锂离子电池铌基氧化物负极材料

锂离子电池负极材料钛酸锂由于其高功率和优异的循环性能得到了广泛的研究,但是较低的比容量(175 m Ah/g)限制了其应用前景。与钛酸锂相比,铌基氧化物具有相似的嵌脱锂电位和更高的比容量,也展现出良好的倍率性能和循环性能,有望成为新型功率型负极材料。本文综述了多种铌基复合金属氧化物(Nb2O5,Ti Nb2O7,Li Nb3O8等)的晶体结构、电化学性能和嵌脱锂机理,讨论了材料的组成、形貌和制备工艺等对其嵌脱锂性能的影响,并概述其作用机制。此外,本文还归纳总结了铌基材料嵌脱锂行为的共性,并比较了它们与钛酸锂的异同,对其作为高功率锂离子电池负极材料的研究趋势和发展前景进行了展望。     

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.     

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.     

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.     

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.     

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.     

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.     

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.