铜包覆多孔硅基材料p-Si@Cu(x)的制备与性能

在球形SiO_2颗粒表面包覆适量的CuO,经还原得到铜包覆的多孔硅复合材料[p-Si@Cu(x)].利用X射线衍射、扫描电子显微镜、透射电子显微镜和比表面积分析等手段对样品的组成、物相结构、微观形貌和孔结构进行分析,并初步研究了材料的循环性能和倍率性能.结果表明,铜包覆量x=0.05时,在100 mA/g电流密度下,样品的首次放电容量为3596.9 mA·h/g,首次充电容量为2590.7 mA·h/g,首次库仑效率为72.03%;在1C倍率下可逆容量为1004.9 mA·h/g,0.1C倍率下循环100周后的可逆容量仍为1706.5mA·h/g,容量保持率为76.1%.     

锂离子电池正极材料LiFePO4电化学性能

分别采用蔗糖和乙炔黑作为碳添加剂,高温固相法合成LiFePO_4复合物,利用X射线衍射、扫描电子显微镜和充放电等测试技术对其晶体结构、表观形貌和电化学性能进行了研究。结果表明,合成的LiFePO_4均为单一的橄榄石型晶体结构。采用蔗糖包覆的LiFePO_4具有更好的电化学性能,以0．2 C充放电,首次放电比容量为148．6 mA·h/g,20次循环后放电容量仍为140．3 mA·h/g。     

V2O3空心球的制备及在锂硫电池中的应用

在NH₃辅助下将制备的V₂O₅空心球高温还原为V₂O₃空心球, 并利用透射电子显微镜、 扫描电子显微镜、 X射线衍射和X射线光电子能谱等手段对材料的形貌与结构进行表征. 将V₂O₃空心球与硫机械混合后, 不经过熔融复合直接作为锂硫电池的正极材料. 电化学测试结果显示, 在0.2C倍率下, 电池首次放电比容量达到1375 mA·h/g, 循环100次后放电比容量可以维持在815 mA·h/g; 在1C高倍率下, 电池首次放电比容量为710 mA·h/g, 经过500次循环后, 放电比容量仍能达到530 mA·h/g, 表明V₂O₃空心球的加入能够有效提高锂硫电池的循环性能.     

阴离子嵌入型炭正极材料的制备及电容性能

通过循环伏安、恒流充放电和扫描电子显微镜等方法,对在1500和2800℃下进行热处理的针状焦炭(NC)的微观结构及作为正极材料的储能特性进行研究,考察了石墨化程度对材料储能性能的影响.2种热处理NC在有机电解液中,当电流密度为50 mA/g时,放电比容量分别为70.1和90.6 mA·h/g;当电流密度为5 A/g时,2种NC的放电比容量为55 mA·h/g左右;而商用活性炭当电流密度为50 mA/g时,比容量只有35.9 mA·h/g.2个NC在1 A/g的电流密度下循环1000次的保持率分别为95.7%和89.2%.     

氮杂碳原位包覆Cu2O/Co3O4@C异质结构复合材料的设计构筑及高效储锂性能

通过液相法合成了Cu₂O纳米立方体, 并在其基础上利用金属有机框架化合物(MOFs)的自组装形貌调控, 进一步构建了层级多孔Co₃O₄和氮杂碳双壳层的Cu₂O/Co₃O₄@C异质结构复合材料. 利用X射线衍射(XRD)、 扫描电子显微镜(SEM)、 透射电子显微镜(TEM)、 热重分析(TGA)、 BET比表面积及孔径分析、 拉曼光谱和X射线光电子能谱(XPS)等表征手段证实了Cu₂O/Co₃O₄@C异质结构复合材料的成功构筑. 双壳层结构设计和丰富的层级孔道结构有效抑制了材料在充放电循环过程中的体积膨胀, 材料在循环100次后仍保持了原有的形貌和构造. 表面多孔结构对电解液的充分浸润、 异质结构的界面内建电场以及缺陷氮杂碳的表面包覆有效提升了材料的电子和离子导电能力. 异质结构设计、 形貌调控、 多孔特性和氮杂碳的协同作用, 使得Cu₂O/Co₃O₄@C复合材料呈现出优异的电化学性能, 在0.1 A/g电流密度下的首次放电比容量达到2065 mA·h/g, 在 2 A/g电流密度下的可逆放电比容量高于360 mA·h/g, 在1 A/g电流密度下循环350次后仍有530 mA·h/g的高可逆放电比容量.     

微波-固相复合加热技术合成LiNi0.5Co0.5O2及其性能研究

用高分子分散及微波-固相复合加热技术合成了层状锂离子电池正极材料LiNi0.5Co0.5O2. 采用循环伏安、充放电循环、扫描电子显微镜(SEM)以及X射线粉末衍射(XRD)等测试技术, 研究了煅烧条件对材料微观形貌、相结构以及电化学性能的影响规律. 研究结果表明: 在750 ℃煅烧4 h即可得到形状为类球形的纯相层状LiNi0.5Co0.5O2正极材料, 该材料的最大放电容量达到154 mA·h/g, 循环10周后放电容量仍保持在148 mA·h/g以上.     

N掺杂C包覆Li_4Ti_5O_(12)锂离子电池负极材料的制备与性能

以TiO2和Li2CO3分别作为钛源和锂源,聚苯胺(PANI)作为碳源和氮源,通过球磨辅助高温固相法合成N掺杂C包覆Li4Ti5O12.通过X射线衍射仪(XRD)、X射线光电子能谱仪(XPS)、元素分析仪(EA)、扫描电子显微镜(SEM)及透射电子显微镜(TEM)等对材料的结构和形貌进行了表征,并将合成材料制成电极片组装成扣式电池,测试其电化学性能.结果显示,钛源的处理对样品的性能有影响,通过对TiO2预包覆合成的N掺杂C包覆Li4Ti5O12具有优异的电化学性能,在碳、氮源的包覆比例(PANI与Li4Ti5O12的质量比)为5%时效果最佳:1C放电时其比容量为157.6mA·h/g,20C放电时其比容量仍可达到119.6mA·h/g;在10C充放电循环100次后,其比容量保持率为97.8%,表明N掺杂C包覆Li4Ti5O12具有优异的倍率性能和循环稳定性.     

用作锂离子电池负极的FeS2微球的制备及性能

以氯化亚铁和硫代硫酸钠为原料, 采用水热法一步合成了由FeS₂纳米片堆积的FeS₂微球. 通过调控铁源与硫源的摩尔比及水热合成时间, 并结合X射线衍射(XRD)和扫描电子显微镜(SEM)表征结果推测了FeS₂的生长机理, 筛选出最优条件以提升其电化学性能. 电化学测试结果表明, 在500 mA/g的电流密度条件下, 材料的首次放电/充电容量可分别达到905和800 mA·h·g ^-1, 首次库伦效率达到88.4%; 在2000 mA/g的大电流密度条件下, 500次放电/充电循环后依然稳定保持350 mA·h·g ^-1的可逆容量.     

SiO_2/C复合负极材料的制备及其性能

采用在纳米SiO2表面包覆聚苯胺,并经过热处理后,制备了SiO2/C纳米复合材料.通过X射线衍射(XRD)、热重分析(TGA)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)对材料的晶体结构和表观形貌进行了表征.同时也对材料的电化学性能进行了测试,结果表明,50 mA/g电流密度下,SiO2/C纳米复合材料首次放电比容量达到830.5 mAh/g,100次循环后,放电比容量仍然保持在510 mA/g以上.电化学交流阻抗测试表明,SiO2表面包覆的碳层能显著减小电极的界面阻抗,提高电池的电化学性能.     

煅烧温度对锂离子正极材料Li[Ni0.475 Mn0.475 Co0.05]O2结构和电化学性能的影响

应用高温固相合成法制备L i[N i0.475Mn0.475Co0.05]O2.XRD,SEM,循环伏安及充放电容量测试表明,在800℃下煅烧合成的样品具有较高的嵌锂容量和良好的循环稳定性,如在20 mA/g和2.3~4.6 V的电压范围内,其首次放电比容量为178.8 mAh/g,循环30周后放电比容量仍能达到150.2 mAh/g,容量损失16.0%.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.     

Catalyst free,visible-light promoted photoaddition reactions between C60 and N-trimethylsilylmethyl-substituted tertiary amines for synthesis of aminomethyl-1,2-dihydrofullerenes

An efficient and benign method for the preparation of aminomethyl-substituted fullerenes has been developed. The process, involving catalyst free, visible-light irradiation of 10% EtOH-toluene solutions containing fullerene C₆₀ and N-trimethylsilylmethyl-substituted amines by using a 20 W compact fluorescent lamp, leads to formation of aminomethyl-substituted fullerene adducts in a highly efficient manner. The photoaddition reaction takes place via a pathway initiated by visible light absorption by C₆₀, followed by SET from the amine to the triplet excited state of C₆₀. Ethanol-promoted desilylation of the resulting a minimum radical then generates the corresponding α-amino radical which couples with the C₆₀ radical anion to form the anion precursor of the fullerene adducts. The new approach using visible-light takes place under mild conditions and it does not require the use of photocatalysts. Thus, the method developed in this effort could broadens the range of functionalized fullerene derivatives that can be readily prepared.     

Highly efficient and stereoselective cycloaddition of nitrones to indolyl- and pyrrolylacrylates

The reactions of various nitrones with indolyl- and pyrrolylacrylates proceeds regioselectively with high diastereoselectivity in the case of aldonitrones, and represents an effective method for obtaining new indolyl- and pyrrolyl-substituted isoxazolidine carboxylates stabilized by weak (CH?O) and moderate (NH?N) strength intramolecular hydrogen bonding. The resulting cycloadducts exhibit promising in vitro anti-influenza activities.     

Transition metal-free direct amination of benzoxazoles using formamides as nitrogen sources

A transition metal-free method for the direct amination of benzoxazoles using formamides as nitrogen sources is reported, which was mediated by an inexpensive and environmentally friendly tetrabutylammonium iodide/tert-butyl hydroperoxide system and gave the 2-aminobenzoxazole derivatives with moderate to good yields.     

l-Proline-catalyzed five-component domino reaction leading to multifunctionalized 1,2,3,4-tetrahydropyridines

Multifunctionalized 1,2,3,4-tetrahydropyridines are concisely synthesized in good yields via l-proline-catalyzed or l-proline/FeCl₃-cocatalyzed one-pot multicomponent reactions (MCRs). The MCRs involve a domino hydroamination/prins reaction/Mannich-type reaction/intramolecular dehydration-cyclization process. The molecular structure of 5baa, one of multifunctionalized 1,2,3,4-tetrahydropyridines, was confirmed by single-crystal X-ray diffraction.     

Exploring the scope of the Gewald reaction: Expansion to a four-component process

An efficient four-component reaction was developed to take advantage of the reactivity of the 2-aminothiophene-3-carbonitrile functionality, which is obtained during the classical three-component Gewald reaction. Various α-methylene bearing ketones were reacted with malononitrile, elemental sulfur, and aryl/heteroarylnitrile derivatives in t-BuOH/NaOH to afford 2-arylthieno[2,3-d]pyrimidin-4-amines in high yields. Preliminary studies revealed the photophysical properties of the products and their potential for use as metal sensors.