掺杂对正极材料LiNi0.8Co0.2O2电化学性能的影响

论述了近年来元素掺杂改善正极材料LiNi0.8 Co0.2 O2电化学性能的研究现状。对层状结构的稳定性与电化学性能的关系进行了分析，对不同的元素掺杂效果进行了比较。认为在优化合成条件的基础上，元素掺杂是提高锂离子电池正极材料电化学性能最有效的途径之一。     

Photoluminescent and Electroluminescent Properties of Ligand Emitting y^3＋, La^3＋, Gd^3＋ and Lu^3＋ Complexes

The photolumineseent (PL) and eleetroluminescent (EL) properties of a series of ligand emitting rare earth complexes (including y^3 , La^3 , Gd^3 and Lu^3 ) were systematically studied. These complexes have the same anionic ligand, 1-phenyt-3-methyl-4-isobutyryl-5-pyrazoloneate (PMIP), and three neutral ligands, triphenyl phosphine oxide(TPPO), 2, 2‘-dipyridine (Bipy) and phenanthroline (Phen). Measured with 60 nm thin film of these complexes vaporized in vacuum on quartz substrates, a good regularity in the PL properties was observed. For rational comparison, the same structural EL devices based on these complexes, ITO/PVK (40 nm)/the complex (80 nm)/Mg: Ag (200 nm)/Ag (100 nm), were fabricated. Excluding the exeiplex emission happens, the EL luminance usually increases with the increasing of PL efficiency.     

高温球磨烧结合成LiCoxMn2-xO4

采用液相法合成前驱体，并通过高温球磨烧结法合成了LiCoxMn2-xO4正极材料。考察Co掺杂量对材料的相结构、形貌、电化学性能的影响。结果表明，Co掺杂后材料的首次放电比容量随着Co掺杂量的增大逐渐减小，而循环性能较好。其中LiCo0.05Mn1.95O4的首次放电比容量达到119.0 mAh/g，在不同倍率下循环100次后的容量保持率为92.52%，表现出很好的电化学可逆性和循环稳定性。     

碳酸盐共沉淀法合成LiNi1/3Co1/3Mn1/3O2及其电化学性能

以碳酸盐共沉淀法合成了Ni1/3Co1/3Mn1/3CO3前驱体,然后以Ni1/3Co1/3Mn1/3CO3和LiOH·H2O为原料,合成出了层状锂离子电池正极材料Li Ni1/3Co1/3Mn1/3O2.通过XRD,SEM和电化学测试对Li Ni1/3Co1/3Mn1/3O2材料的结构、形貌及电化学性能进行了测试和表征.结果表明,800℃烧结12 h所合成的样品粒度大小分布比较均匀,以0.2 C充放电,其首次放电容量为153 mAh·g-1,循环30次后容量为140 mAh·g-1.     

正极材料LiNi1/3Co1/3Mn1/3O2的Mg掺杂及电化学性能

为提高正极材料LiNi_1/3Co_1/3Mn_1/3O₂的循环性能, 采用氢氧化物共沉淀法对前驱体进行Mg掺杂, 再经过混锂、球磨、高温煅烧后, 分别对掺杂与未掺杂的正极材料进行了XRD、SEM及电化学性能的比较.研究结果表明:掺杂与未掺杂的正极材料都为标准的α-NaFeO₂型层状结构, 粒度大小无明显变化; 对于掺杂量为0.03与未掺杂的正极材料, 首轮放电比容量分别为138.2 mAh/g和145.3 mAh/g; 而循环50轮的放电比容量则分别为131.1 mAh/g和119.5 mAh/g.由此可见, 通过Mg掺杂, 正极材料的首轮放电比容量虽有少量降低, 而循环性能却有明显增强.      

Enhanced Emission of Eu^3＋ in Boron Ions-Doped Sol-Gel SiO2 Phosphors

Enhanced Emission of Eu~(3 ) in Boron Ions-Doped Sol-Gel SiO_2 Phosphors     

Study on （Y, Gd）3（Al, Ga）5O12：Ce^3＋ Phosphor

(Y1-a,Gda ) 3 - x (Al1-b, Gab) 5O12 : Cex^3 was synthesized by high-temperature solid state reaction in reducing atmosphere based on high purity raw materials. The influences of y^3 , Gd^3 , A1^3 , Ga^3 and activator-Ce^3 on the performance of the phosphor were investigated. Ce^3 is the luminescent center and activates the phosphor after it replaces Y partially. When x is less than 0.12, the volume of the crystal and the emission intensity of the phosphor increase with the quantity of Ce^3 . When CeO2 is added too much, the phase CeAlO3 will appear. The excitation and emission peaks of the phosphor will shift to longer wavelength when the amount of Gd^3 increases. The wavelength of the emission peak can shif tabout 20 nm when a equals 0.45. In opposite, the excitation and emission peaks will shift to shorter wavelength, when part of Al^3 is replaced by Ga^3 . The wavelength of the emission peak can shift about 20 nm when b equals 0.55.Through the replacemeat of Y^3 or Al^3 by Gd^3 or Ga^3 , the emission peak of the phosphor can be adjusted from 520 to 560 nm. In this way, the phosphor is more suitable for different chips.     

固相烧结辅助高温球磨合成LiNi_xMn_(2-x)O_4

以氢氧化锂、硝酸镍、二氧化锰为原料,用固相烧结辅助高温球磨方法,合成了具有Ni掺杂的LiMn_2O_4正极材料。研究了Ni在不同掺杂量时对材料的相结构、形貌和充放电性能的影响,并与未掺杂Ni的LiMn_2O_4进行对比。结果表明,掺Ni后材料的放电比容量随着掺杂量的增大逐渐减小,而材料的容量保持率相比未掺杂时略有提高;当掺杂量x=0.05时,所得产物的充放电性能最佳,首次放电容量达到122.9mAh/g,充放电容量保持率在40次循环后为97.48%。     

碳源对Li3V2(PO4)3正极材料性能的影响

采用高温碳热还原法在惰性气氛下合成单斜晶型Li3V2(PO4)3正极材料,考察活性炭、蔗糖和酚醛树脂等不同碳源对目标材料性能的影响。采用XRD、FE-SEM和电化学测试等手段对目标材料进行结构表征和性能测试。结果显示,以酚醛树脂作为碳源的正极材料具有优良的电化学性能,首次放电比容量达138 mA.h/g,到第10次循环容量降至122.9 mA.h/g。酚醛树脂作碳源能在加热的过程中固化交联成三维的网状结构,极有效地限制了粒子的进一步长大,材料粒径最小。     

Research on cathode material of Li-ion battery by yttrium doping

Modification of LiFePO4, LiMn2O4 and Li1 xV3O8 by doping yttrium was investigated. The influences of doping Y on structure, morphology and electrochemical performance of cathode materials were investigated systematically. The results indicated that the mechanisms of Y doping in three cathode materials were different, so the influences on the material performance were different. The crystal structure of the three materials was not changed by Y doping. However, the crystal parameters were influenced. The crystal parameters of LiMn2O4 became smaller, and the interlayer distance of (100) crystal plane of Li1 xV3O8 was lengthened after Y doping. The grain size of Y-doped LiFePO4 became smaller and grain morphology became more regular than that of undoped LiFePO4. It indicated that Y doping had no influence on crystal particle and morphology of LiMn2O4. The morphology of Li1 xV3O8 became irregular and its size became larger with the increase of Y. For LiFePO4 and Li1 xV3O8, both the initial discharge capacities and the cyclic performance were improved by Y doping. For LiMn2O4, the cyclic performance became better and the initial discharge capacities declined with increasing Y doping.     

具有核壳结构的高电压正极材料Li(Co_(0.9)Ni_(0.05)Mn_(0.05))O_2的制备与表征

以共沉淀法制备的Ni-Mn包覆Co_3O_4前驱体和Li_2CO_3为原料,通过高温固相法制得了具有核壳结构的锂电池正极材料Li(Co_(0.9)Ni_(0.05)Mn_(0.05))O_2.用扫描电镜(SEM)、X射线能谱仪(EDS)、X射线衍射(XRD)和充放电测试表征了样品的形貌、晶体结构和电化学性能.结果表明,所制备的核壳结构Li(Co_(0.9)Ni_(0.05)Mn_(0.05))O_2具有良好的电化学性能,在3.0~4.5 V和3.0~4.6 V,0.2 C下首次放电容量分别达到180.5 m A·h·g~(-1)和201.3 m A·h·g~(-1),在1 C下,循环50周后容量保持率分别为89.3%和63.3%.     

喷雾干燥法合成锂离子电池复合正极材料xLiFePO4.yLi3V2(PO4)3及性能研究

采用喷雾干燥和高温固相法合成了一系列xLiFePO4·yLi3 V2( PO4)3复合正极材料.电化学测试结果表明,0.95LiFePO4·0.05Li3 V2( PO4)3复合正极材料具有较高的比容量、优良的循环性能和倍率性能,在电压范围为2.0V～4.3V,0.1C,1C,5C条件下的放电容量分别为162.7,147.7和122.3 mAh·g-1.0.5LiFePO4·0.5Li3 V2(PO4)3和0.3LiFePO4·0.7Li3 V2 (PO4)3复合正极材料则表现出了良好的倍率性能,5C,10C充放电条件下容量保持率分别为:77％,73％,88％,82％.     

Influences of Nd~（3＋） doping on structure and electrochemical performance of layered Li_（1.05）V_3O_8

Nd3+-doped Li1.05V3O8 was synthesized by liquid-state reactions combined calcination.The influences of Nd3+ doping on physical and electrochemical performances of Li1.05V3O8 were investigated using X-ray diffraction (XRD),cyclic voltammograms,a.c.impedance and galvanostatic charge-discharge tests,etc.Results indicated that Nd3+-doped products had well developed crystal structure of layered LiV3O8 and uniform particle size distribution.Nd3+ doping with a proper amount improved the initial discharge capacity,discharge voltage and ion conductivity of the cathode material to some extent.Nd3+ did not participate in the electrochemical reactions and was beneficial to stability of the crystal structure during cycling.     

Solution combustion synthesis and electrochemical properties of yttrium-doped LiMnPO_4/C cathode materials for lithium ion batteries

Phospho-olivine pristine LiMnPO_4/C and yttrium-substituted LiMn_(1-x)Y_xPO_4/C(x=0,0.01,0.03,0.05)were synthesized by a solution combustion method.The effects of Y-doped on structure,morphology and electrochemical performances were investigated.From powder X-ray diffraction pattern,all substituted materials adopt an identical structure to that of the LiMnPO_4 olivine structure,suggesting that the yttrium ion was well inco rporated into the crystal lattice,without any changes in the host crystal structure.The electrochemical impedance spectroscopy provides clearly that yttrium-substituting reduces the charge transfer impedance and improves the lithium ion diffusion through the structure.When x=0.01,the material shows an excellent capacity and stability during charge/discharge process.The initial specific discharge capacity can reach up to 156.84 mAh/g at C/20,with a coulombic efficiency of about 96.11%,which is 14% higher than that of the pristine material.The results confirm that the cyclic stability and the electrochemical performances of LiMnPO_4/C are highly improved by Y-doping.     

熔盐法合成LiMn_（1/3）Ni_（1/3）Co_（1/3）O_2及AA电池的电化学性能

以KCl为熔盐,采用熔盐法合成了锂离子电池正极材料LiMn1/3Ni1/3Co1/3O2,扫描电子显微镜（SEM）显示此方法制备产物具有较好的晶形,颗粒较均匀.XRD表征结果显示产物为层状结构,充放电测试结果显示出材料在3.6 V平台附近有较大的可逆容量.在900℃时保温8 h时合成的LiMn1/3Ni1/3Co1/3O2具有较好的电化学性能,制作成AA电池,在2.75～4.2 V之间进行充放电测试,在1 C倍率下放电,LiMn1/3Ni1/3Co1/3O2的初始放电容量可达132.9 mAh/g,循环50多次后容量仍为124.6 mAh/g,容量保持率为93.75﹪.     

Influence of Sc3+ on LiMn2O4 cathode materials at elevated temperature

Sc3 -doped lithium manganese oxides were synthesized by solid-state reaction. The influences of doping element on structure,mean valence of manganese, and electrochemical performances were studied by X-ray diffraction (XRD), galvanostatic charge-discharge and cyclic voltammetric tests, and also electrochemical impedance spectroscopy (EIS). XRD tests showed that doped lithium manganese oxides were pure spinel structure without other phases. Redox titration and visible spectrophotometry tests indicated that the mean valence of man-ganese in doped lithium manganese oxides was higher than that of pure one. LiSc0.02Mn1.98O4 remained 92.9% of the initial specific discharge capacity after 50th cycle at a constant current of 50 m/g, and the reversibility of LiSc0.02Mn1.98O4 was improved in comparison with pure LiMn2O4 at 50 ℃. EIS indicated that film deposition on spinel particles was suppressed because of Sc3 doping, and the charge transfer be-tween the surface film and spinel particles with increasing temperature for Sc3 -doped materials became easier as compared with undoped one.     

Influence of lanthanum doping on performance of LiFePO4 cathode materials for lithium-ion batteries

Using solid-state synthesis method,a series of samples of lanthanum doped Li1-xLaxFePO4(x=0.0025,0.005,0.0075,0.01) were prepared.Each cathode structural and electrochemical properties were investigated using X-ray diffractometry(XRD),scanning electron microscopy(SEM),electrochemical impedance spectroscopy(EIS) and charge/discharge cycling.Nanopowders material with single-phase could be obtained.The reversible capacity could be drastically improved by the introduction of La.The optimum cells with Li0.99La0....     

Synthesis and electrochemical properties of Ce-doped LiNi_（1/3）Mn_（1/3）Co_（1/3）O_2 cathode material for Li-ion batteries

The layered material of Ce-doped LiNi1/3Mn1/3Co1/3O2 with α-NaFeO2 was synthesized by a co-precipitation method. X-ray diffraction (XRD) showed that Ce-doped LiNi1/3Mn1/3Co1/3O2 had the same layered structure as the undoped LiNi1/3Mn1/3Co1/3O2. The scanning electron microscopy (SEM) images exhibited that the particle size of Ce-doped LiNi1/3Mn1/3Co1/3O2 was smaller than that of the undoped LiNi1/3Mn1/3Co1/3O2. The Ce-doped LiNi1/3Mn1/3Co1/3O2 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram (CV), and electrochemical impedance spectra (EIS). The optimal doping content of Ce was x=0.02 in the LiNi1/3-xMn1/3Co1/3CexO2 samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through Ce-doping. The improved electrochemical performances of the Ce-doped LiNi1/3Mn1/3Co1/3O2 cathode materials were attributed to the addition of Ce4+ ion by stabilizing the layer structure.