多元稀土掺杂锂锰氧正极材料的结构及性能表征

采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、电池性能测试系统研究了多元稀土掺杂锂锰氧正极材料的相结构、形貌,并对其活化性能、循环稳定性能进行了表征。结果表明:采用Pechini法合成多元稀土掺杂LiMn2O4样品时,只有将掺杂元素的含量严格控制在一定范围内,所合成的LiMn2O4、LiLa0.03Mn1.97O4、LiLa0.012Ce0.012Mn1.976O4、LiLa0.012Nd0.012Mn1.976O4、LiCe0.012Nd0.012Mn1.976O4样品才具有纯尖晶石型LiMn2O4结构。当稀土掺杂元素含量较高时,所合成的LiLa0.015Ce0.015Mn1.97O4、LiLa0.015Nd0.015Mn1.97O4、LiCe0.015Nd0.015Mn1.97O4样品由LiMn2O4相及微量杂质相CeO2、Nd2O3、CeO2+Nd2O3组成。所有样品呈规则的近球形或球形,其粒径范围为0.5～2.8μm。适量的稀土元素掺杂将使LiMn2O4材料的初始容量减小、充放电效率及循环稳定性能增加,LiCe0.012Nd0.012Mn1.976O4样品具有较好的综合电化学性能,其初始容量为123.5mAh/g,经30次循环充放电后的容量为113.2mAh/g,为相同条件下LiMn2O4样品放电容量的1.27倍。     

稀土元素对LiMn_2O_4电极材料相结构及性能的影响

采用X射线衍射仪、扫描电子显微镜、电池测试系统等研究了不同稀土掺杂元素La、Ce、Nd等对Pechini法合成的LiMn2O4材料的相结构、形貌及电化学性能的影响规律.结果表明,合成的LiMn2O4、LiLa0.03Mn1.97O4、LiLa0.01Ce0.01Nd0.01Mn1.97O4样品具有纯尖晶石型LiMn2O4结构,LiLa0.015Ce0.015Mn1.97O4样品由LiMn:O.相及微量杂质相CeO2组成;样品呈规则的近球形或球形,其粒径范围为0.5～2.5μm.稀土元素取代使LiMn2O4材料的初始容量略有降低、循环稳定性能有较大增加,LiMn2O4、LiLa0.03Mn1.97O4、LiLa0.015Ce0.015Mn1.97O4、LiLa0.01Ce0.01Nd0.01Mn1.97O42样品的初始容量分别为126.0、120.0、117.3、124.0 mA·h/g,经30次循环充放电后的容量分别为88.9、102.7、101.6、109.1 mA·h/g.     

表面掺杂Al的球形尖晶石LiMn2O4的高温循环性能

采用控制结晶工艺合成了球形Mn3O4，通过在球形Mn3O4的表面包覆Al（OH）3，然后与LiOH一起混合焙烧制备了表面掺杂Al的尖晶石LiMn2O4。采用SEM，XRD，EDS以及电池系统测试等方法，研究了所制备材料的结构和性能。SEM分析表明：表面掺杂后，Al（OH）3均匀地包覆在颗粒表面。XRD和EDS分析表明：焙烧后，Al元素占据了Mn的位置，且颗粒表面的Al含量高于其总体的平均含量，说明Al只是在表面富集，即表面掺杂。电池测试表明：表面掺杂后，尖晶石LiMn2O4的初始充放电容量有所下降，但在高温55℃下的循环性能有显著的提高，表面掺杂6％Al的尖晶石LiMn2O4 50次循环的容量保持率从68．3％提高到79．0％。说明以Al^3＋作为掺杂离子通过表面掺杂来改善LiMn2O4的高温循环性能是有效的。     

溶胶-凝胶法制备LiCoxMn2-xO4及电化学性能研究

采用溶胶-凝胶(sol-gel)法制备了颗粒较小(100～300nm)、分布均匀的尖晶石LiCoxMn2-xO4粉体,研究了不同掺杂水平对其结构及电化学性能的影响.结果表明,掺杂少量Co于LiMn2O4中并不改变材料的尖晶石结构;随着Co掺杂量增加,材料结构稳定性提高,极化降低,首次放电比容量逐渐减小,但充放电循环性能却明显改善;在低温(500℃)条件下退火6h后,LiCoxMn2-xO4粉体的放电比容量稍有增加,但对循环性能影响不大;在电流密度0.1mA/cm2和截止电压3.5～4.4V时,LiCo0.1Mn1.9O4粉体首次放电比容量达123mAh/g,20次循环后的稳定放电比容量为106mAh/g,具有较好的电化学性能.     

Mg、F复合掺杂尖晶石LiMg0.1Mn1.9O3.95F0.05的合成和电化学行为研究

以己二酸为配位体采用溶胶-凝胶法合成了LiMn2O4,Mg掺杂或Mg和F复合掺杂的尖晶石锂镁氧化物正极材料.对合成出的样品采用X-射线衍射仪、X-光电子能谱、扫描显微电子镜、循环伏安测试和充放电测试仪进行了详细的研究.X-射线衍射结果表明,所有的样品都具有相同的纯尖晶石相,LiMg0.1Mn1.9O4和LiMg0.1Mn1.9O3.95F0.05与LiMn2O4的样品相比,具有较小的晶格参数和晶胞体积.X-光电子能谱试验结果表明,在LiMn2O4中,Mn3 和Mn4 的相对量分别为50.2%和49.8%,而LiMg0.1Mn1.9O3.95F0.05中Mn3 和Mn4 的相对量分别为48.4%和51.6%.扫描电镜结果显示,LiMg0.1Mn1.9O3.95F0.05颗粒尺寸略小、尺寸分布窄,形态结构更为规整.循环伏安实验显示,Mg和F复合掺杂的尖晶石具有更好的可逆性.LiMn2O4,LiMg0.1Mn1.9O4,LiMg0.1Mn1.9O3.95F0.05样品的首次放电能量和能量保持率分别为123、111、114 mAh·g-1和86.5%、92.3%、90.9%,且LiMg0.1Mn1.9O4和LiMg0.1Mn1.9O3.95F0.05具有比LiMn2O4更高的库仑效率.     

耐久型高倍率性能锰酸锂微球的合成(英文)

以Mn2+和NH4HCO3为原料,通过控制结晶法合成球形MnCO3前驱体模板。以LiNO3和MnCO3为原料,按照一定的摩尔比机械混合,在700°C下煅烧8h,合成高倍率性能和长循环性能的球形尖晶石LiMn2O4材料。分别考查原料的摩尔比、反应时间以及反应温度对前驱体MnCO3形貌和产率的影响。采用X射线粉末衍射和扫描电镜对合成的MnCO3和LiMn2O4进行表征,对LiMn2O4样品进行室温条件下的充放电性能测试。电化学测试结果表明:尖晶石锰酸锂微球在10C的放电倍率下的首次放电容量达90mA·h/g(1C放电容量为148mA/g),800次循环后容量保持率达到75%。该方法合成的LiMn2O4微球作为高功率型锂离子电池的正极材料有着较好的应用前景。     

以Mn3O4为前驱体制备尖晶石型LiMn2O4及其性能

采用改进的固相反应法合成了高性能的锂离子电池正极材料LiMn2O4。首先,以廉价的MnSO4为原料,通过水解氧化法制备纳米级Mn3O4前驱体;然后,将Mn3O4和Li2CO3混合均匀,在750℃固相反应20 h,得到尖晶石型LiMn2O4。用X射线衍射(XRD)和扫描电镜(SEM)对Mn3O4前驱体和LiMn2O4样品进行表征,用充放电测试和循环伏安技术对LiMn2O4样品进行电化学性能研究。结果表明:所制备的LiMn2O4具有完整的尖晶石型结构,且晶体粒子分布均匀。所制备的LiMn2O4材料在3.0~4.4 V之间,室温(25℃)下,在0.2C倍率下首次放电比容量为130.6 mA.h/g;在0.5C倍率下首次放电比容量为127.1 mA.h/g,30次循环后,容量仍有109.5 mA.h/g,且样品具有较好的高温性能。     

熔融浸渍法LiMn2O4的制备及性能

利用电解二氧化锰（EMD）和碳酸锂为原料，采用熔融浸渍法合成了尖晶石型锂锰氧化物LiMn2O4，并用热重分析（TGA）、粉末X射线衍射技术研究了合成条件对产物的晶体结构、电化学性能的影响。研究结果表明，在合成的后续阶段反应时间的长短对产物的晶体结构和电化学性能的影响很大，时间长，会使LiMn2O4分解为Li2MnO3和Mn2O3;LiMn2O4的初始放电比容量也随反应时间的延长而下降。在最佳条件下合成的LiMn2O4的首次放电比容量高达132.4mAh/g，50次循环后的放电比容量还保持在125.6mAh/g的水平。     

F-掺杂LiMn2O4的合成及电化学性能

采用溶胶-凝胶法合成掺杂F^-的LiMn2O4。通过XRD、SEM对掺杂F-的LiMn2O4材料的组成、结构、微观形貌等进行分析与表征,测试不同F^-掺杂量的LiMn2O4在常温（20℃）、高温（55℃）下的电化学性能。结果表明：所合成的材料具有良好的尖晶石立方结构,无杂相;F^-的掺杂提高了材料的比容量,增强了材料的稳定性,改善了其在高温下的循环性能。当F^-的掺入量x由0增加到0.1时,材料的比容量由119.7 mA.h/g增加到124.9 mA.h/g,高温下充放电30个循环后容量保持率由79.4%增加到84.4%。     

高温固相法合成尖晶石型LixMn2O4的结构及电化学性能

采用X射线衍射仪、扫描电子显微镜、电池测试系统等研究了Li/Mn(摩尔比)、合成温度、合成时间等工艺因素对LixMn2O4正极材料的相组成、形貌及电化学性能的影响.结果表明,当合成温度为1023～1223 K,合成时间为12～36 h时,所合成的LixMn2O4(x=0.98～1.05)样品具有单一的尖晶石型LiMn2O4结构,样品呈规则的球形或近球形,粒径为1～3μm.样品具有较好的室温活化特性,首次活化即达到最大放电容量118.0 mAh/g,样品的放电容量随合成时问的延长而增加、随合成温度的升高呈增后减的规律.     

Synthesis and characterization of Li_(1.3)Al_(0.3)Ti_(1.7)(PO_4)_3-coated LiMn_2O_4 by wet chemical route

Li1.3Al0.3Ti1.7(PO4)3-coated LiMn2O4 was prepared by wet chemical route. The phase,surface morphology,and electrochemical properties of the prepared powders were characterized by X-ray diffraction,scanning electron micrograph,and galvanostatic charge-discharge experiments. Li1.3Al0.3Ti1.7(PO4)3-coated LiMn2O4 has similar X-ray diffraction patterns as LiMn2O4. The corner and border of Li1.3Al0.3Ti1.7(PO4)3-coated LiMn2O4 particles are not as clear as the uncoated one. The two powders show similar values of l...     

Preparation and characterization of LiMn1. 5 Me0.5O4（Me=Ti, Fe, Ni, Zn） for lithium-ion battery cathode materials

Based on synthesizing pure spinel type lithium manganese oxides, the derivations such as LiMn1.5Ti0.5O4, LiMn1.5Fe0.5O4, LiMn1.5Ni0.5O4 and LiMn1.5Zn0.5O4 were prepared using solid-step-sintering method. The structures were characterized by using XRD, SEM and laser granulometer. The electrochemical measurement results show that the element of iron or nickel can raise the discharging plateau voltage of LiMn2O4 , and element titanium improves the electrochemistry property of LiMn2O4 little, while element zinc destroys the electrochemistry property of LiMn2O4. The influence of elements of titanium, iron, nickel, or zinc on the structure of LiMn2O4 pure phase was discussed from the viewpoint of structural chemistry.     

Preparation of modified LiMn2O4 by solid-state reaction

Modified lithium manganese oxides were prepared by solid-state reaction of LiMn2O4 and LiCoO2 as raw materials. A study was carried out by TG-DSC,XRD, DSC and electrochemical to analyse the reaction process and structural characterization of products. The results show that the LiMn2O4 reacts chemically with LiCoO2 at high temperature. All of Li and partial Co atoms can insert into the LiMn2O4 crystal lattice and a newly formed spinel phase-modified LiMn2O4 was obtained. The distribution of Co content is even in modified LiMN2O4 compound. The modified LiMn2O4 compound exhibits improved cycling stability at room and elevated temperature in comparison with the pure LiMn2O4.     

锂离子电池正极材料锰酸锂派生物LiMn1.75Me0.25O4(Me=Ti, Fe, Ni)的制备与表征

在合成纯相尖晶石型锰酸锂的基础上 ,采用固相分段法制备了锰酸锂派生物LiMn1.75Ti0 .2 5O4 ,LiMn1.75Fe0 .2 5O4 和LiMn1.75Ni0 .2 5O4 。用XRD ,SEM和粒度测试仪分别对试样进行了表征。电化学检测表明 ,Fe和Ni元素能够提高锰酸锂的放电平台电压 ,Ti元素不能改善锰酸锂的电化学性能。从结构化学角度初步探讨了Fe ,Ni和Ti元素对纯相尖晶石型锰酸锂结构的影响。     

Performance and capacity fading reason of LiMn2O4/graphite batteries after storing at high temperature

Spinel LiMn2O4 was synthesized by a solid-state method. A 204468-size battery was fabricated and stored at 55℃. The structure and mor-phology of the LiMn2O4 cathode were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (gEM) technique. Energy dispersive spectroscopy (EDS) was used to analyze the surface component of the carbon anode. The discharge capacities of LiMn2O4 stored for 0, 24, 48, and 96 h are 106, 98, 96, and 92 mAh-g-1, respectively. The cyclic performance is improved after storage. The capacity reten-tions of LiMn2O4 stored for 0, 24, 48, and 96 h are 83.8%, 85.8%, 86.9%, and 88.6% after 180 cycles. The intensity of all the LiMn2O4 dif-fraction peaks is weakened. Mn is detected from the carbon electrode when the battery is stored for 96 h. Cyclic voltammograms and elec-trochemical impedance spectroscopy (EIS) were used to examine the surface state of the electrode after storage. The results show that the re-sistance and polarization of LiMn2O4/electrolyte is increased after storage, which is responsible for the fading of capacity.     

Electrochemical performances and structure characteristic of LiMn2O4-xYx（Y=F, Cl, Br） compounds

Spinel LiMn2 O4-x Yx (Y=F, Cl, Br) compounds were prepared by solid-state reaction and the electrochemically galvanostatic charge-discharge cycles were performed using as-prepared compounds as cathode material. The influence of halogens on their lattice constants and the relation of electrochemical properties and their lattice constants were investigated. It is concluded that when the lattice constants are smaller than that of LiMn2O4, the reversible capacity fade is suppressed and the initial capacity sacrifice is observed. When the content of fluorine is 0.05, the lattice constant of LiMn2O3.95 F0.05 is larger than that of LiMn2O4, the initial capacity is improved. An efficient method was found to control the lattice constants of LiMn2O4 through the addition of halogen, and to improve the electrochemical performance of LiMn2O4. The LiMn2O3.95 F0.05 shows excellent electrochemical charge-discharge performance, with high initial capacity of 143 mAh/g and nearly no capacity loss after 116 cycles.     

Structure and electrochemical properties of LiMn2O4

LiMn2O4, a cathode material of lithium ion battery, was prepared by the citric acid complexing method using lithium acetate and manganese acetate as raw materials. The type of atom location confused degree, the confused degree and judgement method in LiMn2O4 were analyzed. The effect of sintering temperature on structure and electrochemical properties of LiMn2O4 was also investigated. The results show that the atom location confused degree increases with the decrease of the X-ray diffraction peak intensity ratio of LiMn2O4, Ⅰ111/Ⅰ311. The type of atom location confused degree depends on the variation tendency of Ⅰ111/Ⅰ311 and Ⅰ311/Ⅰ400 value. If the variation tendency is the same, it belongs to the 16c type location confusion, however, if the variation tendency is contrary, it belongs to the anti-spinel type location confusion. When the sintering temperature is low, it is apt to produce the anti-spinel location confusion in LiMn2O4. With the increase of sintering temperature, the confused degree with the anti-spinel type gradually reduces, however, the confused degree with 16c type increases to some extent. When the atom location confusion with the anti-spinel type appears in LiMn2O4, both the initial discharging capacity and cycling properties of LiMn2O4 reduce. However, the atom location confusion with 16c type does not affect the charge and discharge properties of LiMn2O4.     

Synthesis and character of spinel LiMn2O4

1　INTRODUCTIONTheincreasingconcernsonportableelectricele mentsdemandmoreandmoreelectrochemicalener gy .Countriesallovertheworldhaveputlargequan tityofmanuallabors ,materialresourcesandfinancialresourcesonbasicresearchanddevelopmentonnewtypeofrechargeablebatteries[1,2 ] .However ,thisnewtypeofbatteriesisbasedonstudyinganddevel opingperfectperformanceofmaterials ,especiallyonmaterialsofthelithiumbatteries.LixMn2 O4 cathodematerialshavebeenwidelystudiedoverthelasttwodecadesasapotentialcand…     

Improving the electrochemical performance of LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript>/graphite batteries using LiF additive during fabrication

LiMn2O4/graphite batteries using LiF additive were fabricated and their electrochemical performance including discharge,cycling and storage performances were tested and compared with LiF-free LiMn2O4/graphite batteries.The LiMn2O4/graphite battery with LiF added shows better capacity (107.5 mAh/g),cycling performance (capacity retention ratio of 93% after 100 cycles),and capacity recovery ratio (98.1%) than the LiF-free battery.The improvement in electrochemical performance of the LiF-added LiMn2O4/graphite...