Preliminary studies of mn-rich Li[Li(x)(Ni0.3Co0.1Mn0.6)1-x]O2 (x = 0.09, 0.11) as cathode active materials for lithium rechargeable batteries

Novel cathode active materials, Li[Li(x)(Ni0.3Co0.1Mn0.6)1-x]O2 (x = 0.09, 0.11) composed of rod-like primary particles, but aggregated spherical shape in appearance, were synthesized. The newly Mn-rich cathode active materials were then adopted as cathodes to show the benefits for Li-ion rechargeable batteries. The results show that to use proper nano-scaled particles as a cathode and to make homogeneous particle sizes have great improvements on electrochemical performances, probably ascribed to enhancement of charge transfer kinetics and lower cell impedance at high voltage region (approximately 4.6 V). The electrochemical performances of Mn-rich cathodes were investigated by cycler (BT2000, Arbin), comparing electrochemical behaviors between room and elevated temperature, 55 degtees C. The morphology of cathodes having nano-scaled particles of active materials and the Mn-rich cathode active materials were investigated using field emission scanning electron microscope (FE-SEM) and field emission transmission electron microscope (FE-TEM), also the crystalline phase identification was analyzed by high power X-ray diffractometer (XRD).     

Preparation and characterization of Li[Ni(x)M(y)Mn(1-x-y)]O2 (x = 0.3, y = 0.2) (M = Mg, in, Gd) as positive electrodes for lithium rechargeable batteries

Mn-rich layered Li[Ni0.3M0.2Mn0.5]O2 (M = Mg, In, and Gd) cathode active materials were synthesized by a simple sol-gel method and comparative studies of those materials depending on doping elements were carried out.     

富锂正极材料Li1+x[Ni0.36Mn0.64]1-xO2的制备及电化学性能研究

采用氢氧化物共沉淀-高温固相焙烧法合成了富锂正极材料Li1+x[Ni0.36Mn0.64]1-xO2(x=0.12,0.15,0.18,0.2)。采用XRD表征其结构,SEM表征其形貌,恒电流充放电和循环伏安测试其电化学性能。其中,XRD结果表明各样品都具有α-NaFeO2型层状结构。结果表明:室温下以30mA/g的电流密度,在4.6~2.75V的电压范围内充放电,x=0.15的首次放电比容量为237.9mAh/g,经50次循环后容量保持率为98%。研究发现,层状富锂镍锰正极材料中的Li2MnO3组分在充放电过程中会逐渐向尖晶石相转变,这是容量衰减的主要原因。     

富锂锰基正极材料Li1.2Ni0.13Co0.13Mn0.54O2的Zn2+掺杂改性

采用高温固相合成法制备富锂锰基正极材料Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.54-x)Zn_xO_2(x=0,0.03,0.06,0.10),Zn~(2+)掺杂对Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.54)O_2的表面特性和电化学性能都有影响。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、拉曼光谱分析、充放电测试、倍率特性测试、循环性能测试,分析了该合成材料的晶体结构、形貌特征、微观结构和电化学性能。富锂锰基正极材料为a-NaFeO_2层状结构,R-3m空间群,结晶度高,结构稳定性好,其中Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.48)Zn_(0.06)O_2的电化学性能较好。掺杂Zn~(2+)可以提高富锂锰基正极材料的充放电比容量、倍率性能、循环性能等电化学性能。     

正极材料zLi2MnO3·（1-z）LiNi0.4Mn0.4Co0.2O2的合成与性能

富锂锰过渡金属层状正极材料以其成本低、安全、容量高受到广泛关注,X射线衍射（XRD）和电化学性能测试显示以共沉淀结合煅烧成功合成富锂层状正极材料zLi2MnO3.（1-z）LiMn0.4Ni0.4Co0.2O2（z=0.2,0.4,0.6）。其中z=0.4组分的放电容量达到210mAh/g（2-4.8V,0.05C）,远高于z=0.6组分,而经20个充放电循环的稳定性也优于z=0.2组分。微分容量分析表明z=0.2组分中因Ni/（Co＋Mn）比值较大和Li2MnO3含量较少可能导致其容量逐渐衰减。z=0.6则因所含LiMn0.4Ni0.4Co0.2O2量较少,造成其放电容量较低;z=0.4拥有最佳Li2MnO3及LiMn0.4Ni0.4Co0.2O2组合使其容量和循环性能最好。     

Improvement in high-temperature thermoelectric properties by adding Mn for Co in Ca3Co4O9

Nano-sized Ca3Co(4-x)Mn(x)O9 (0 < or = x < or = 0.6) thermoelectric powders were synthesized by solution combustion method, using aspartic acid as fuel. The microstructure and high-temperature (500-800 degrees C) thermoelectric properties of the Ca3Co(4-x)Mn(x)O9 were investigated. The addition of Mn for Co in Ca3Co(4-x)Mn(x)O9 resulted in a decrease of the electrical conductivity and a significant increase of the Seebeck coefficient. Consequently, the power factor was remarkably enhanced by the addition of Mn. Ca3Co(3.7)Mn(0.3)O9 sample showed the highest value of the power factor (1.24 x 10(-4) Wm(-1) K(-2)) at 800 degrees C. We believe that the Ca3Co(4-x)Mn(x)O9 is strongly desirable as a novel high-temperature thermoelectric material for power generation.     

锂离子电池正极材料的研究进展

综述了近年来发展起来的一些锂离子电池正极材料 ,主要包括嵌锂的层状LixMO2 结构和尖晶石型LixM2 O4 结构的过渡金属氧化物 (M =Co、Ni、Mn、Cr等 )。重点介绍了锂钴氧化物、锂镍氧化物、锂锰氧化物的性能、制备、结构以及改性方法等 ,并对纳米电极材料和其它正极材料的发展情况作了简介     

锂离子电池正极材料LiNi0.5FexMn1.5-xO4的电化学性能

以醋酸锂、醋酸锰、醋酸镍、草酸铁为原料,采用溶胶凝胶法制备出了4.6 V高电位材料LiNi0.5-FexMn1.5-xO4。合成化学计量比为n(Li)∶n(Mn)∶n(Ni)∶n(Fe)=1.3∶1.5-x∶0.5∶x(x=0,0.02,0.03,0.04)。在空气条件下于450℃下煅烧6h,再于800℃下烧结18h。对合成的材料用X射线衍射仪分析晶体结构和用扫描电镜(SEM)观察微观形貌,对电池进行首次充放电测试和循环效率测试。实验结果表明,LiNi0.5FexMn1.5-xO4三元正极材料为立方晶系,Fd3m空间群。以其为正极材料组装的锂离子电池在x=0.03时,充放电比容量为126mA·h·g-1。     

Nano/micro lithium transitionmetal (Fe, Mn, Co and Ni) silicate cathode materials for lithium ion batteries

Lithium transitionmetal (Fe, Mn, Co, Ni) silicate cathode materials are new promising substituting cathode materials for lithium ion batteries. They had caught the researchers' eyes in the past several years. Nowadays, there are growing interests for silicate cathode materials in the field of lithium ion batteries. Among the silicate cathode materials, Li2FeSiO4 is the most promising cathode materials because of its high structure stability, high reversible capacity, high electronic conductivity and the abundant resource of iron and silicon. Although Li2MnSiO4 and Li2CoSiO4 have much higher theoretic specific capacity than Li2FeSiO4, they all have inferior electrochemical behaviours due to different reasons. There are only calculation results about Li2NiSiO4 till now. This brief critical review firstly discussed some papers about the first-principle calculation of Li2MSiO4 (M=Fe, Mn, Co Ni), and then collects and discusses relevant papers and recent patents about the fabrication, structure, particle size and electrochemical performance of nano/micro Li2MSiO4 (M=Fe, Mn, Co Ni) and their composites. Finally, the future challenges of Li2FeSiO4 are also discussed.     

Layered Li0.88[Li0.18Co0.33Mn0.49]O2 nanowires for fast and high capacity Li-Ion storage material

Layered Li0.88[Li0.18Co0.33Mn0.49]O2 nanowires are prepared using Co0.4Mn0.6O2 nanowires and lithium nitrate as precursors at 200 degrees C via a hydrothermal method for fast and high capacity Li-ion storage material. The obtained nanowires exhibit a reversible capacity of 230 mAh/g between 2 and 4.8 V, even at the high current rate of 3600 mA/g.     

新型层状Li-Ni-Mn-O锂离子电池正极材料的研究

对近几年有关层状Li-Ni-Mn-O作为锂离子电池新型正极材料的研究进行了系统分析.比较了不同的合成方法及组成对材料性能的影响.对层状Li-Ni-Mn-O的结构研究及LixMnyNi1-yO2中Ni和Mn的价态研究做了系统分析与比较.其中LiNi1/2Mn1/2O2和LiNi0.2Li0.2Mn0.6O2是比较好的;超额Li对材料性能有利.对层状Li-Ni-Mn-O性能的改进提出了进一步改进的措施;认为应该发展低温合成方法及步骤尽量少的共沉淀法和简单燃烧法,优化和降低Ni的含量,掺杂一种或多种高价金属元素是很有前途的方法.     

锂离子电池正极梯度材料的制备及电性能研究

采用金属离子混合硫酸盐溶液分次共沉淀法制备前躯体,混锂后通过高温固相反应得到具有镍、钴和锰浓度梯度的层状LiNi0.56Co0.22Mn0.22O2锂离子电池正极材料。通过x射线衍射(XRD)、扫描电子显微镜(SEM)及恒电流充放电测试对合成的材料进行了表征。结果表明,750～900℃焙烧15h下合成的产物均具有典型的α-NaFeO2型层状结构特征,晶型结构完整,粒度均匀。800℃合成的正极材料具有较好的电化学性能。在充放电倍率0.4C、2.75-4.2V电压范围内,材料的首次充放电比容量分别为170.0mAh/g和131.8mAh/g,放电效率为77.5%;第51次循环的充放电比容量分别为131.3mAh/g和130.5mAh/g,放电效率为99.4%,容量保持率达到99.0%。     

Crystallization mechanisms of phase change (GeSbSn)(100-x)Co(x) optical recording films

In this study, the (GeSbSn)(100-x0Co(x) films (x = 0-13.3) were deposited on natural oxidized silicon wafer and glass substrate by dc magnetron co-sputtering of GeSbSn and Co targets. The ZnS-SiO2 films were used as protective layers. The thicknesses of the (GeSbSn)(100-x)Co(x) films and protective layer were 100 nm and 30 nm, respectively. We investigated the effects of Co addition on the thermal property, crystallization kinetics, and crystallization mechanism of the GeSbSn recording film. The crystallization temperatures of (GeSbSn)(100-x)Co(x) films were decreased with Co content. It was found that the activation energy of the (GeSbSn)(100-x)Co(x) films will decrease from 1.53 eV to 0.55 eV as Co content increased from 0 at.% to 13.3 at.%.     

LiMxMn2-xO4正极材料的表面改性机理研究

采用溶胶-凝胶包裹法对尖晶石LiMn2O4及其阳离子掺杂LiM0.1Mn1.9O4(M=Li，Ni)正极材料进行了表面改性研究．X射线衍射及电子探针线扫描分析表明，表面改性以后的晶粒仍为尖晶石结构，表面改性离子Co的浓度由表及里逐步减小．电解液溶蚀实验及电化学循环测试表明，表面改性后的正极材料LiM0.1Mn1.9O4的抗溶蚀性明显增强，循环性能优良．性能改善的原因是表面改性以后，尖晶石晶粒表层Mn^3 离子浓度降低，Mn^4 离子浓度大大增加，减少了Mn^3 发生歧化反应的机会．     

Thermoelectric properties of nanocrystalline Ca(3-x)Cu(x)Co4O9 (0 < or = x < or = 0.32) for power generation

We successfully synthesized nano-sized Ca(3-x)Cu(x)Co4O9 (0 < or = x < or = 0.32) powders by solution combustion process. Plate-like grains and porous structure were observed in the sintered Ca(3-x)Cu(x)Co4O9 ceramics. The sintered Ca(3-x)Cu(x)Co4O9 showed a monoclinic symmetry. The electrical conductivity of the Ca(3-x)Cu(x)Co4O9 increased with increasing temperature, indicative of a semiconducting behavior. The added Cu led to a significant increase in the electrical conductivity. The Seebeck coefficient of the Cu-added Ca(3-x)Cu(x)Co4O9 was much higher than that of the Cu-free Ca3Co4O9. The highest power factor (9.99 x 10(-4) Wm(-1)K-2) was obtained for Ca2.76Cu0.24Co4O9 at 800 degrees C.     

LiNix Co1-xO2合成条件对-其结构与性能的影响

研究了在空气下固相结合成LiNixCo1-xO2的工艺及反应预处理方式,不同锂源,温度,和配比等因素对产品结构与性能的影响,结果表明,采用LiOH为锂源,采取混合研磨后压块以及烘干Ni(OH)2,Co(OH)2后加入氢氧化锂的预处理方式更有利于合成反应的进行,在600℃预烧一段时间的下,750℃恒温合成的产物比650℃,850℃保温合成的产物层状结构更明显,首次充电容量更高,在一定范围内,随合成时间的增长,产物的衍射峰强度增大,结构更完整,电性能更好,按镍钴的不同配比,均能合成结构良好的LiNixCO1-xO2,而配比为n(Li):n(Ni):n(Co)=1.15:0.3:0.7时合成的产物初始容量较高,达到156.146mAh/g.     

Magnetic and magnetocaloric properties of nanocrystalline Pr(1-x)A(x)Mn(1-y)Co(y)O3 (A = Ca, Sr) (x = 0.3; y = 0.5) manganites

Structural, magnetic and magnetocaloric properties of sol-gel prepared, nanocrystalline oxides Pr(1-x)A(x)Mn(1-y)Co(y)O3 (A = Ca, Sr) (x = 0.3; y = 0.5) (cubic, space group Fm3m) have been studied. From the X-ray data, the crystallite size of Pro.7Ca0.3Mn0.5Co0,503 and Pr0.7Sr0.3Mn0.5Co0.5O3 samples is found to be approximately 24 nm and approximately15 nm respectively. High resolution transmission electron microscopy image shows average particle size of approximately 34 nm and approximately 20 nm. Magnetization measurements indicate a Curie temperature of approximately 153 K and approximately172 K in applied magnetic field of 100 Oe for Pr0.7Ca0.3Mn0.5Co0.5O3 and Pr0.7Sr0.3Mn0.5Co0.O3 compounds. The magnetization versus applied magnetic field curves obtained at temperatures below 150 K show significant hysteresis and magnetization is not saturated even in a field of 7 T. The magnetocaloric effect is calculated from M versus H data obtained at various temperatures. Magnetic entropy change shows a maximum near T(c) for both the samples and is of the order approximately 2.5 J/kg/K.     

Comprehensive understanding of Li/Ni intermixing in layered transition metal oxides

With the development of high energy density battery technology, layered transition metal oxide cathode materials, particularly Ni-rich layered cathodes of Li-ion batteries are urgently required due to its high energy density. However, Li/Ni intermixing inevitably occurs in Ni-rich cathode materials and affects the materials in terms of structure and performance. This review comprehensively summarizes the causes of Li/Ni intermixing and analyzes its inevitability due to ionic radius, Ni migration, magnetic interactions, and thermal stability. In addition, the effect of Li/Ni intermixing on materials is summarized, particularly its benefits, which have not yet been comprehensively examined. Finally, the methods for regulating Li/Ni intermixing that corresponds to its causes are presented in detail. This review can help researchers fully understand Li/Ni intermixing and propose solutions for the current shortcomings of Li/Ni intermixing research and directions for future studies.     

锂离子电池正极材料Li3V2-2x/3Mnx（PO4）3的溶胶凝胶法合成和电化学性能

以CH3COOLi·2H2O、V2O5、Mn(CH3COO)2·4H2O、(NH4)2HPO4和蔗糖为原料,采用溶胶–凝胶法合成了掺锰磷酸钒锂/碳(Li3V2-2x/3Mnx(PO4)3/C)复合正极材料,用XRD、XPS、SEM、电化学性能对样品进行了表征.测试结果表明,少量锰的掺杂并未改变Li3V2(PO4)3/C的单斜结构,Li3V1.94Mn0.09(PO4)3中的Mn和V分别以+2和+3价存在,其颗粒类似球形,直径比较均匀且小于200 nm,并表现出良好的电化学性能.在0.1C倍率和3.0～4.8 V电压内,该样品的首次充、放电容量分别为182.1和168.8 mAh/g,放电效率高达92.69%,而且100次循环后,其放电比容量仍是首次放电容量的77.4%.     

Synthesis and self-assembly of ultrathin Ni(x)Fe(1-x)(OH)2 nanodiscs via a wet-chemistry method

Self-assembled ultrathin Ni(x)Fe(1-x)(OH)2 nanodiscs have been synthesized by using a wet-chemistry method. The uniformity and the assembly of Ni(x)Fe(1-x)(OH)2 nanostructures are sensitive to the iron ion concentration in the precursor. An optimum iron concentration of 10% results in the formation of uniform ultrathin Ni(x)Fe(1-x)(OH)2 nanodiscs with a typical side length of 50 nm and a thickness of 10 nm. They are also self-assembled by connecting their (001) facets with in-plane orientation and form a chain-like microstructure. Lattice relaxation is present within several atomic layers at the interfaces between two adjacent nanodiscs, which introduces about 6 degrees misalignment of these nanocrystals. Analytical electron microscopy analysis reveals that the iron additive atoms distribute uniformly in the nanodiscs and they are substitution atoms of Ni atoms. It has been found that the iron species is critical to the formation and assembly of the hexagonal nanodiscs.