层状锂离子正极材料Li_(1+x)(Co_(0.2)Ni_(0.4)Mn_(0.4))O_2的结构和电化学性能的研究

采用溶胶凝胶法,用柠檬酸作为鳌合剂,在不同的温度下合成制备均一的层状锂离子正极材料Li(Co0.2Ni0.4Mn0.4)O2。XRD、SEM实验数据表明,在较低温度700°C下便可制得层状Li1+x(Co0.2Ni0.4Mn0.4)O2,并具有均一的颗粒形貌,颗粒大小为300 nm左右。XPS显示其正极材料中的Co、Ni、Mn的化学价态分别为+3,+2,+4,均为它们的稳定价态。700°C下合成的材料在20mA/g,2.9~4.6 V电压范围内,首次放电比容量为210.2 mAh/g,50周后放电比容量仍高达185.3 mAh/g,容量损失为11.84%。     

铷掺杂三元正极材料Li1-xRbxNi0.4Co0.2Mn0.4O2的制备及其电化学性能

采用共沉淀法制备了三元材料LiNi0.4Co0.2Mn0.4O2,掺杂不同比例铷进行改性,对其进行了结构表征,考察了其电化学性能. 结果表明,Li0.97Rb0.03Ni0.4Co0.2Mn0.4O2样品的结晶度较好,铷掺杂起到了稳定三元材料晶体结构的作用,有效改善了材料的电化学性能,5C倍率下放电比容量达130 mA?h/g.     

钴、铝掺杂对Li_(1.1)Ni_(0.4)Mn_(0.4)Co_(0.15)Al_(0.05)O_2结构和电化学性能的影响

采用草酸盐共沉淀法合成Li1.1Ni0.4Mn0.4Co0.15Al0.05O2正极材料,通过XRD分析,计算得出掺杂后晶胞体积收缩,层状结构更加稳定。恒电流充放电测试显示了其良好的充放电性能和循环稳定性。对于不同充电状态的EIS分析,显示其较小的电荷转移阻抗及较好的电荷转移动力学。     

钠离子电池正极材料Na(Mn_(0.4)Fe_(0.2)Ni_(0.35)Mg_(0.05))O_2的制备及电化学性能研究

采用溶胶-凝胶法合成钠离子电池正极材料Na(Mn_(0.4)Fe_(0.2)Ni_(0.4))O_2,并对其进行Mg元素掺杂合成Na(Mn_(0.4)Fe_(0.2)Ni_(0.35)Mg_(0.05))O_2材料,分别对2种材料的表面形貌、结构以及电化学性能进行了研究。结果表明:掺杂合成的样品Na(Mn_(0.4)Fe_(0.2)Ni_(0.35)Mg_(0.05))O_2同样具有O3型层状结构,虽然首次放电比容量降低至125.6 m Ah/g,但是其循环性能和倍率性能却明显优于原始样品。在循环50次之后,其放电比容量仍可达114.7 m Ah/g,对应的容量保持率为91.3%。在1 C倍率下,仍能释放出90.1 m Ah/g的可逆容量。此外,交流阻抗结果表明,该材料具有更小的电荷转移阻抗。     

不同锂比Li1+xNi0.4Co0.2Mn0.4O2+δ材料的合成

锂离子正极材料主要集中在钻系、镍系、锰系、铁系.镍钻锰酸锂三元材料以其更低的制备成本和较好的电化学性能也引起了人们的广泛关注.目前对于三元材料的合成一般是先通过氧氧化物共沉淀法,在氨水的辅助下先合成前驱体,然后再经过高温烧结合成目标材料.这种前驱体合成方法对工艺参数要求高,较难稳定控制,并且氨水的使用对环境将造成污染.本文通过碳酸盐共沉淀法合成(Ni0.4Co0.2Mn0.4)CO3,前驱体来避免上述问题,并且通过合理的制备过程,以不同锂比合成Li1+xNi0.4Co0.2Mn0.4O2+δ材料.     

烧结温度对LiNi0.5Co0.3Mn0.2O2物理及其电化学性能的影响

以共沉淀法制备出的球形Ni0.5Co0.3Mn0.2(OH)2为前驱体,以碳酸锂为锂源,通过高温固相法合成了球形LiNi0.5Co0.3Mn0.2O2正极材料。通过热重分析(TGA/DSC)、X射线衍射(XRD)、扫描电子显微镜(SEM)、粒度分布、以及电化学性能的测试考查了不同烧结温度对LiNi0.5Co0.3Mn0.2O2的物理性能及电化学性能的影响。结果表明,900℃下烧结得到的LiNi0.5Co0.3Mn0.2O2晶体结构完整、球形形貌规则、粒度分布均匀,并表现出了优异的电化学性能,0.2 C首次放电容量达到了166.7 mA.h/g;1 C首次放电容量为151.6 mA.h/g,20次循环后,容量保持率高达97.9%。     

锂离子电池正极材料LiNi0.5Co0.2Mn0.3O2合成工艺优化

以球形三元前驱体Ni0.5Co0.2Mn0.3(OH)2以及LiOH.H2O为原料,用正交实验优化锂离子电池正极材料LiNi0.5Co0.2Mn0.3O2合成工艺,考察烧结温度、保温时间以及锂与金属元素(Ni、Co、Mn总量)物质的量比等因素对材料电化学性能的影响。得到最佳条件:烧结温度为800℃,保温时间为12 h,锂与金属元素物质的量比为1.06。按最佳工艺合成的样品在0.2 C、1 C首次放电比容量分别为165.1 mA.h/g和151.6 mA.h/g,且表现出良好的循环稳定性。     

Li[Ni1/3Co1/3Mn1/3]O2合成工艺对其结构和性能的影响

采用碳酸盐共沉淀法制备Li[Ni1/3Co1/3Mn1/3]O2。研究了前驱体合成温度、时间和焙烧温度、焙烧时间对材料结构和电化学性能的影响。测试结果表明,合成温度为40℃,时间30 h所得前驱体的振实密度和电化学性能较好。XRD测试结果表明,不同焙烧温度下得到的Li[Ni1/3Co1/3Mn1/3]O2均具有α-NaFeO2型层状结构。其中800℃下焙烧15 h得到的样品具有较好的层状结构和较低的阳离子混排程度。样品在2.8～4.3 V电压范围内,0.2 C放电倍率下的首次放电比容量最高可达159.1 mAh·g-1,循环50次后容量保持率为95.7%。     

改进固相法合成LiNi_xCo_yMn_(1-x-y)O_2正极材料及性能研究

采用固相法制备正极材料LiNi1/3Co1/3Mn1/3O2,用X射线衍射仪(XRD)、扫描电子显微镜(SEM)/透射电镜(TEM)分析材料的结构和形貌特征,用LAND电池测试系统测试材料的电化学性能(充放电容量和循环性能等)。以LiOH.H2O,H2C2O4.2H2O,Ni(AC)2.4H2O,Co(AC)2.4H2O和Mn(AC)2.4H2O为原料,采用固相法在不同煅烧温度和煅烧时间下制备的层状正极材料LiNi1/3Co1/3Mn1/3O2具有典型的α-NaFeO2型层状结构特征,晶型结构完整。电化学性能测试结果表明,在850℃下保温15 h合成的正极材料电化学性能最优,在电流密度为120 mA/g、充放电电压在2.75~4.5 V时,经30次循环后放电比容量为163.5 mA.h/g,容量保持率为94%;50次循环后为157.2 mA.h/g,容量保持率为90.8%。     

超级电容器电极材料MnS_(0.4)O_(0.8)的制备及其电容行为研究

采用液相共沉淀法制备了一种含Mn、S、O的无定型粉末材料,元素分析结果表明其组成为MnS0.4O0.8。采用XRD、SEM对其进行了物理表征。通过循环伏安和恒流充放电研究了其电容行为。结果表明:在1mol.L-1Na2SO4溶液中该材料具有良好的电容性能。当扫描速度为2mV.s-1时,其比电容为131F.g-1,经历500循环后其比电容还能保持初始值的94.8%,表现了良好的稳定性。恒流充放电实验结果表明材料的可逆性良好。此材料可作为电化学超级电容器的一种新的候选材料。     

Ionic conductivity of apatite-type solid electrolyte ceramics Ca2−xBaxLa4Bi4(SiO4)6O2 (0≤x≤2)

A complex impedance of oxyapatites Ca_2?xBa_xLa₄Bi₄(SiO₄)₆O₂ (0≤x≤2) prepared by solid state reaction has been investigated. The formation of apatites has been checked by X-ray diffraction, FTIR, Raman and ²⁹Si MAS-NMR techniques. The electric impedance data indicate that relaxation phenomena are strongly dependent on temperature in the 923–1048 K range. The bulk resistance decreases with increasing temperature, showing a typical negative temperature coefficient of resistance (NTCR). ac-Conductivity measurements have been performed on a wide range of frequencies and temperatures. The complex modulus plots have confirmed the presence of bulk contributions. The complex impedance analysis suggests the presence of non-Debye relaxations that would be associated with correlation on ions motion.     

EXTRACTION AND CHARACTERIZATION OF PALLADIUM {4-(2-PYRIDYLAZ0) RES0RCIN0L} COMPLEXES

The extraction of palladium complexes with 4-(2-pyridyl-azo)resorcinol (PAR=H₂R) by tetraphenylphosphonium and tetra-phenylarsonium chlorides in chloroform was investigated. The optimum conditions for the extraction and spectrophotometric determination of palladium in the extract were determined and the extracted species studied. The anionic complex {PdRCl}^? was predominantly extracted over a wide pH range (between 3 and 10) forming ion associates with the cation of the extraction agent. The extracted complexes were studied spectrophoto-metrically in solution and by characterization of the ìsolated solid compounds.     

Sr0.5Zr2（PO4）3陶瓷的力学性能研究

用共沉淀法和低分子有机溶剂分散获得SZP粉体，经干压成型和烧结得到SZP陶瓷。研究了其力学性能与烧结温度烧结时间和添加剂用量的关系。最佳工艺条件为：添加Mg06wt%,1300℃或Zn03wt%,1200℃均烧结1．5小时，SZP陶瓷的抗压强度分别可达244．0MPa和226．2MPa。     

Kinetic model applicable to synthesis of (Cu0·25 N0·25 Zn0·5 )Fe2O4 ferrite

Abstract

A study was undertaken of the reaction whereby (Cu_0·25 Ni_0·25 Zn_0·5 )Fe₂O₄ ferrite is obtained from the corresponding oxides. The effect of synthesis temperature on the ferrite formation rate was determined by means of high temperature X-ray diffractometry (HT-XRD). An empirical model for the reaction was developed based on the hypothesis that diffusion through the product layer is the rate controlling process step. The proposed model was found to satisfactorily reproduce the amount of ferrite that formed as a function of time and temperature (750–1000°C).     

Studies of interfacial layers between 4H-SiC (0 0 0 1) and graphene

The region between epitaxial graphene and the SiC substrate has been investigated. 4H-SiC (0 0 0 1) samples were annealed in a high temperature molecular beam epitaxy system at temperatures between 1100 and 1700 °C. The interfacial layers between the pristine SiC and the graphene layers were studied by X-ray photoelectron spectroscopy. Graphene was found to grow on the SiC surface at temperatures above 1200 °C. Below this temperature, however, sp³ bonded carbon layers were formed with a constant atomic Si concentration. C1s and Si2p core level spectra of the graphene samples suggest that the interface layer we observe has a high carbon concentration and its thickness increases during the graphitization process. A significant concentration of Si atoms is trapped in the interface layer and their concentration also increases during graphitization.     

O-(2-乙基氨基-6-甲基-4-嘧啶基)-O,O-二甲基硫代磷酸酯的合成与表征

以单氰胺为起始原料,经与乙胺胍化、乙酰乙酸甲酯环合、O,O-二甲基硫代磷酰氯缩合得到O-(2-乙基氨基-6-甲基-4-嘧啶基)-O,O-二甲基硫代磷酸酯产品,其结构经核磁、质谱确认,合成总收率为62％(以单氰胺计),产品含量为95％.     

4-甲氧基-N-苯基-N-(4-(2,2-二苯乙烯基)苯基)苯胺的合成

在氮气保护下,以二苯胺、对碘苯甲醚和二苯基氯甲烷为原料,经过Ullmann反应、Vilsmeier-Haack反应和Wittig反应,合成了电荷传输材料4-甲氧基-N-苯基-N-(4-(2,2-二苯乙烯基)苯基)苯胺,收率达到20.1%,通过熔点、红外光谱、核磁共振谱等手段确证了所合成化合物的结构。该合成工艺具有反应温度低,反应时间短,制备简单的优点,并优化了反应条件。并用紫外光谱、荧光光谱测试了其光谱性质。     

4-氯-2-氰基-5-(4-甲基苯基)咪唑的合成研究

以对甲基苯乙酮为起始原料,经二氧化硒氧化制得4-甲基苯基乙二醛,在水与甲醇的混合溶剂中,与盐酸羟胺、乙二醛水溶液环化反应得4-羟基-5-(4-甲基苯基)-2-肟基次甲基咪唑-3-氧,再以N,N-二甲基甲酰胺为溶剂,与二氯亚砜反应脱水氯化得标题化合物,总收率69.0%。     

(S)-4-(2-甲基丁基)-4'-(4-丙基环己基)-2-氟联苯的合成及性能研究

以(S)-(2-甲基丁基)苯为原料,经碘代和Suzuki偶联四步反应,合成了手性液晶(S)-4-(2-甲基丁基)-4'-(4-丙基环己基)-2-氟联苯,总收率11.4%,纯度99.2%,并采用IR、MS、1H NMR及元素分析对其结构进行了表征。结合差示扫描量热仪(DSC)和偏光显微镜(POM)研究了目标化合物的介晶性,并采用Cano’s wedge法测定了目标化合物的扭曲力。