聚苯胺在LiCoO2和LiMn204正极中的双重功能

用化学聚合法合成聚苯胺(PAn),并考察其在LiCoO2和LiMn2O<,4>正极中的双重功能.结果表明:在优化条件下PAn的产率y=94.06%、导电率σ=18.39 S/cm,大于乙炔黑(AB)的导电率σ=7.77 S/cm;以制备的PAn为锂离子电池正极活性材料,在不添加其他导电剂对其进行恒电流充、放电试验(电流密度J=15 mA/g)时,第三循环的比放电容量D3=60.8mA·h/g、充、放电效率n3=94.56%;PAn在正极中兼有活性材料的功能;以LiCoO2和尖晶石LiMn2O<,4>为正极活性材料,以PAn替代AB作为导电剂进行恒电流充、放电试验,在电流密度分别为15、30、45和60 mA/g时,比充、放电容量都增大,表明正极的极化程度减小;正极在经过较大电流密度(60 mA/g)充、放电后,再以小电流密度(15 ma/g)进行充、放电时,比充、放电容量几乎没有变化,表明经较大电流密度(60 mA/g)充、放电后,LiCoO2和尖晶石LiMn2O<,4>的贮锂结构没有改变.     

Al离子掺杂正极材料LiMn2O4的高温循环性能

采用固相反应法分别合成正极材料LiMn2O4和LiAl，Mn2-xO4（x=0．05，0．1，0.3）。对它们进行XRD和SEM测试，并对比了高温下的循环性能。结果显示：除Al掺杂量x=0．3时，合成物出现了LiAlO2杂质相外，其余皆具有单一的尖晶石相结构。掺杂后的晶体颗粒比较圆润。LiMn2O4在高温下经过20次循环后，其比容量降低29％，衰减很快。造成衰减的主要原因是Mn^3＋歧化反应生成的Mn^2＋在电解液中的溶解，以及Jahn—Teller效应。通过阳离子Al^3＋的掺杂，有效的提高了尖晶石LiMn2O4的高温循环性能。     

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。     

新型高安全性锂离子电池正极复合材料

过充性能对于大型锂离子电池如用于电动汽车的电池显得非常重要.报道了一种新型锂离子电池正极材料,即将包埋LiNiCoO2与尖晶石LiMn2O4按照质量比1:1进行混合,能够显著提高聚合物锂离子电池的安全性.与采用纯的LiCoO2为正极的电池相比,采用复合材料的电池具有较好的放电性能(0.5C)、循环性能(1C)、热稳定性(150℃)以及在3C和5C不同充电上限条件下优良的过充性能.采用复合材料的聚合物锂离子电池的各项安全测试表明,所有电池都没有起火或爆炸.试验表明这种复合材料能够替代LiCoO2.     

有机溶剂醇热法对LiCoO2正极表面修饰

采用有机溶剂醇热法,以异丙醇铝为原材料对LiCoO2进行表面处理.通过XRD、SEM对包覆前后正极材料的微观结构进行表征,对包覆前后正极材料的电化学性能进行测试.结果表明:包覆后正极材料的充放电效率明显提高,循环30次后容量保持率由包覆前的84.1%提高到包覆后的93.2%.这归因于包覆后LiCoO2表面形成的Al2O3或LiAlxCo1-xO2层,该层起到阻挡层的作用,有效地抑制Co4 与电解液反应,稳定了LiCoO2结构,提高了电化学循环性能.     

锂离子电池正极材料LiMn1.95Cr0.05O4的电化学性能

采用分段固相法合成了LiMn2O4和掺Cr的LiMn1.95Cr0.05O4电池正极材料。XRD分析证实2种材料都为尖晶石结构，LiMn1.95Cr0.05O4有较小的晶格常数。循环伏安测试显示掺Cr增强了反应可逆性。交流阻抗测试表明，50次循环后，LiMn2O4电池的反应电阻增加了32．1％，LiMn1.95Cr0.05O4电池的反应电阻只增加21．7％，说明掺Cr可减小反应电阻的增加。     

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。     

Al离子掺杂正极材料LiMn2O4的高温循环性能

采用固相反应法分别合成正极材料LiMn2O4和LiAlxMn2-xO4(x=0.05,0.1,0.3).对它们进行XRD和SEM测试,并对比了高温下的循环性能.结果显示:除Al掺杂量x=0.3时,合成物出现了LiAlO2杂质相外,其余皆具有单一的尖晶石相结构.掺杂后的晶体颗粒比较圆润.LiMn2O4在高温下经过20次循环后,其比容量降低29%,衰减很快.造成衰减的主要原因是Mn3+歧化反应生成的Mn2+在电解液中的溶解,以及Jahn-Teller效应.通过阳离子Al3+的掺杂,有效的提高了尖晶石LiMn2O4的高温循环性能.     

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。     

柠檬酸对液相燃烧合成尖晶石型LiMn2O4的影响

以醋酸锰和醋酸锂为原料，柠檬酸为燃料，研究了不同柠檬酸用量及不同硝酸浓度改性对液态燃烧合成法制备尖晶石型LiMn2O4的影响。结果表明，柠檬酸与锰离子的摩尔比≤0．5时，所得产物的主晶相为LiMn2O4，含有极少Mn2O3等杂质；〉0．5时，所得产物主要为Mn2O3，LiMn2O4含量较少。燃烧反应产物中LiMn2O4相对含量随硝酸浓度的升高而增加，当柠檬酸与锰离子的摩尔比为0．1，硝酸浓度为2mol／L时，所得尖晶石型LiMn2O4较纯净且结晶性较好，但晶体粒子尺寸分布不均。     

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.     

Surface modification and characterization of F-Co doped spinel LiMn2O4

Spinel LiCo0.09Mn1.91O3.92F0.08 as cathode material was modified with LiCoO2 by the sol-gel method, and the crystal structure, morphology and electrochemical performance were characterized with XRD, SEM, EDS, AAS and charge-discharge test in this paper. The results show that a good clad coated on parent material can be synthesized by the sol-gel method, and the materialswith modification have perfect spinel structure. LiCo0.09Mn1.91O3.92F0.08 materials coated by LiCoO2 improve the stability of crystal structure and decrease the dissolution of Mn into electrolyte. With the LiCoO2 content increasing, the specific capacity and cycle performance of samples are improved. The capacity loss is also suppressed distinctly even at 55 ℃.     

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.     

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...     

合成温度对LiMn1.95Mg0．05O4结构与性能的影响

用柠檬酸辅助溶胶一凝胶法在不同温度下合成了LiMn1.95Mg0．05O4正极材料。用X射线衍射、充放电测试以及电化学阻抗谱分析技术研究了不同合成温度对LiMn1.95Mg0．05O4结构和电化学性能的影响。结果表明：合成温度对LiMn1.95Mg0．05O4正极材料的晶相结构、电化学性能有显著影响,LiMn1.95Mg0．05O4尖晶石相的生成和长大与其合成的温度有密切的关系,合成的最佳温度为750℃;在750℃条件下合成的LiMn1.95Mg0．05O4具有较高的电化学活性和较好的晶相结构;高温合成有利于提高LiMn1.95Mg0．05O4正极材料的放电容量,低温合成有利于提高其循环性能。     

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.     

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.     

Synthesis and physicochemical properties of LiLa0.01Mnt.99O3.99F0.01 cathode materials for lithium ion batteries

Spinel lithium manganese oxide cathode materials were synthesized using the ultrasonic-assisted sol-gel method.The synthesized samples were investigated by differential thermal analysis (DTA) and thermogravimetry (TG),powder X-ray diffraction (XRD),scanning electron microscopy (SEM),cyclic voltammetry (CV),and the charge-discharge test.TG-DTA shows that significant mass loss occurs in two temperature regions during the synthesis of LiLa0.01Mn1.99O3.99F0.01.XRD data indicate that all samples exhibit the same pure spinel phase,and LiLa0.01Mn1.99O3.99F0.01 and LiLa0.01Mn1.99O4 samples have a better crystallinity than LiMn2O4. SEM images indicate that LiLa0.01Mn1.99O3.99F0.01 has a slightly smaller particle size and a more regular morphology structure with narrow size distribution.The charge-discharge test reveals that the initial capacities of LiMn2O4,LiLa0.01Mn1.99O4,and LiLa0.01Mn1.99O3.99F0.01 are 130,123,and 126 mAh·g-1,respectively,and the capacity retention rates of the initial value,after 50 cycles,are 84.8%,92.3%,and 92.1%,respectively.The electrode coulomb efficiency and CV reveal that the electrode synthesized by the ultrasonic-assistexi sol-gel (UASG) method has a better reversibility than the electrode synthesized by the sol-gel method.     

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.