锂电池阴极材料尖晶石型LiMn2－xLaxO4的研究

采用高温固相法,合成了掺杂改性的锂离子电池阴极材料尖晶石结构的LiMn2－xLaxO4（x=0、0.01、0.02、0.03、0.04、0.05、0.10）.用XRD对材料的晶体结构进行了表征.从材料的晶体结构、充放电测试和循环性能等方面分析了掺杂元素镧在稳定晶体结构中的作用.实验表明，掺杂后的材料在常温和高温下的循环性能均得到了明显改善.而且当掺杂量x≤0.04时，材料有较高的放电比容量.     

正尖晶石LiMn_2O_4电化学性能研究

采用高温固相反应合成了尖晶石LiMn2 O4 锂离子电池正极材料 ,并对其性能进行研究 .综合考察了影响材料电化学性能的主要因素 ,诸如原材料的选择、合成温度、Li/Mn比以及添加金属元素Co等 .研究了材料在高温下的电化学性能和影响因素 ,并分析了LiMn2 O4 在电解质中的溶解和引起容量衰减的原因     

B掺杂尖晶石型LiMn2O4正极材料的制备及长循环电化学性能

采用固相燃烧法制备了单晶多面体尖晶石型LiMn1.94B0.06O4正极材料,利用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)以及充放电测试等手段,对其晶体结构和电化学性能等进行了表征。结果表明,B掺杂没有改变尖晶石型LiMn2O4的晶体结构,促进了(440)和(400)晶面的优先生长,形成了高暴露的(111)晶面及少部分(110)和(100)晶面的单晶多面体LiMn1.94B0.06O4晶粒,减少了Mn的溶解和提供了更多的锂离子扩散通道,其晶粒尺寸在160~350 nm之间。在10C、25℃的条件下,LiMn1.94B0.06O4电极的首次放电比容量可达到103.0 mAh·g^-1,2000次循环后,表现出较好的容量保持率(57.7%);在15C高倍率下,LiMn1.94B0.06O4仍然保持了67.1 mAh·g^-1的首次放电比容量,1500次循环后,仍能维持46.2%的容量保持率;在1C、55℃的条件下,其初始放电比容量高达125.2 mAh·g^-1,表现出良好的高温性能。B掺杂能够有效提高尖晶石型LiMn2O4的高倍率性能和循环寿命,稳定晶体结构,抑制Jahn?Teller效应和缓解Mn的溶解。     

层状化合物La2Ni1-yCoyO4+δ的合成、结构与性能

采用氨基多羧酸配合物法合成La2Ni1-yCoyO4+δ(y=0~0.2)超细粉料, 研究陶瓷样品的结构和混合导电性能. 研究结果表明, La2Ni1-yCoyO4+δ具有正交结构(Fmmm空间群), Co离子取代增加了钙钛矿层中ab平面上Ni/Co—O键的键长、岩盐层中沿c 轴方向上La—O键的键长和非化学计量氧含量, 并有利于改善材料的烧结性能. 随着Co离子含量的增加, 总电导率的峰值温度向高温移动, 高温段总电导率随温度的变化趋于平缓, 但总电导率水平出现降低; 增加Co离子含量还有利于提高氧离子导电性能. Co离子取代对陶瓷样品混合导电性能的影响与晶体结构参数的变化紧密相关.     

Al3+对尖晶石型LiMn2O4正极材料的表面掺杂包覆改性

采用表面掺杂包覆改性的方法对LiMn2O4尖晶石型锂离子电池正极材料进行改性.以Al为表面掺杂元素,Al(NO3)3为原料,研究了Al3+掺杂量为7.1%(原子分数)时不同温度(300、400、500、600、700、750、800℃)下的改性效果.研究发现,随着热处理温度的升高,改性样品的最大比容量先升高后降低,在700℃达到最大值;循环衰减先增大后降低再增大;这是由于随着热处理温度的升高,包覆层逐渐分解并与LiMn2O4颗粒反应固溶,在750℃完全固溶,衰减达到极小值,而后固溶层向颗粒内部扩散,导致包覆层对颗粒免受电解液溶解的保护能力变弱,因而容量衰减增大.其中700℃热处理5h的样品最大比容量为133.6mAh·g-1,循环50周衰减3.4%.研究表明Al3+表面掺杂包覆改性有利于促进LiMn2O4尖晶石型锂离子电池正极材料的商业化生产,具有大规模应用的前景.     

尖晶石LiMn2O4前驱体的低热固相反应法合成机理及其结构与热分解过程研究

以氢氧化锂、醋酸锰和柠檬酸为原料,采用低热固相反应法制备了Li+与Mn2+摩尔比为1∶2的前驱体化合物LiMn2L(Ac)2.通过元素分析、红外光谱、质谱和热重/差热等测试方法对前驱体的组成、结构、合成反应机理及热分解过程进行了研究.结果表明,可在全固相条件下通过低热固相反应得到锂离子与锰离子达到分子级混合水平的前驱体,该前驱体在350℃下焙烧4h即可出现明显的尖晶石相LiMn2O4产物.     

Sc3+ 掺杂的尖晶石型LiMn2 O4 正极材料制备及性质

A series of Sc3+-doped spinel lithium manganese oxides Li1+xScyMn2-yO4（y=0.01, 0.02, 0.06, and 0.10）were synthesized by solid state reaction using LiOH·H2O, MnO2, and Sc2O3 as starting materials. The results of powder X-ray diffraction indicated that the doped Li1+xScyMn2-yO4 maintain the cubic structure of spinel phase Fd3m. The electrochemical properties were characterized by electrochemical methods. The initial discharge capacity reached 135 mAh/g and the capacity fading rate was less than 2% after 40 cycles. The spinel phase was well preserved after 40 cycles. The doping of Sc3+ effectively improved the cycleability of spinels, and was a promising way for the improvement of spinel LiMn2O4 cathode materials.     

Li3PO4包覆LiMn2O4正极材料的结构表征和电化学性能

采用共沉淀法在尖晶石LiMn2O4颗粒表面包覆Li3PO4.XRD、SEM研究结果表明,包覆后的材料仍为尖晶石结构,粒径均匀.电化学性能测试表明,Li3PO4包覆层的存在,减少了正极材料与电解液的直接接触,抑制了高温下电解液对LiMn2O4材料的侵蚀,从而有效改善了高温下材料的循环性能.在40℃时,包覆样品的比容量衰减率都低于未包覆样品,其中包覆1%Li3PO4的样品的初始比容量为110.4mAh/g,50次循环后比容量为84.1mAh/g.     

Lithium manganese spinel materials for high-rate electrochemical applications

In order to successively compete with supercapacitors, an ability of fast discharge is a must for lithium-ion batteries. From this point of view, stoichiometric and substituted lithium manganese spinels as cathode materials are one of the most prospective candidates, especially in their nanosized form. In this article, an overview of the most recent data regarding physico-chemical and electrochemical properties of lithium manganese spinels, especially, LiMn2O4 and LiNi0.5Mn1.5O4, synthesized by means of various methods is presented, with special emphasis of their use in high-rate electrochemical applications. In particular, specific capacities and rate capabilities of spinel materials are analyzed. It is suggested that reduced specific capacity is determined primarily by the aggregation of material particles, whereas good high-rate capability is governed not only by the size of crystallites but also by the perfectness of crystals. The most technologically advantageous solutions are described, existing gaps in the knowledge of spinel materials are outlined, and the ways of their filling are suggested, in a hope to be helpful in keeping lithium batteries afloat in the struggle for a worthy place among electrochemical energy systems of the 21st century.     

锂离子电池掺钴正极材料电子结构的DV-Xα研究

The electronic structures of electrode material LiMn2O4 and Li5Mn7CoO8 for the lithium ion battery are studied by employing an ab initio “atomic-basis + norm-conserving non-local pseudopotentias” method. The calculation results of the electronic structure of an ode material LiMn2O4 show that the valence band of LiMn2O4 are mainly made up of 3d atomic orbtics of Mn(8) and Mn(9), and 2 p atomic orbits of O(7), O(6) and O(4), while the conduction band contains essentially 3d orbits of Mn (8) and Mn (9), and 2p atomic orbits of O(7). At the same time, the computing results of electronic structure of electrode material Li5Mn7CoO8 indicate that the reversible capacity of the electrode can decrease and discharge voltage reduces in the cycling, and the net charge of partial lithium ions of the active electrode material and the interaction between lithium ions and oxygen ions increase. While the cycling performance of the anode can improve due to the structural stabilization of the material Li5Mn7CoO8 corresponding to the decrease of the valence band width and enhancement of the Co-O bond.     

锂离子电池LiMn2O4薄膜电极的制备研究进展

尖晶石ＬｉＭｎ２Ｏ４是最有希望替ＬｉＣｏＯ２的新一代锂离子电池阴极材料。高能、轻量、超薄将是未来锂离子电池一个十分重要的发展方向。本文对尖晶石ＬｉＭｎ２Ｏ４的晶体结构作了简要介绍。综述了近年来在ＬｉＭｎ２Ｏ４薄膜电极制备方面的研究进展,包括静电喷雾沉积（ＥＳＤ）、静脉激光沉积（ＰＬＣ）、射频磁溅射（ＲＦＭＳ）等等,并对今后的研究方向进行了展望。     

LiMn_2O_4的高温比容量衰减研究

采用高温固相法合成了LiMn2 O4电极材料 ,运用电化学和阴极膜X射线衍射等方法研究了LiMn2 O4在高温 (≥ 50℃ )下 ,循环时比容量衰减的现象及其衰减机理。结果表明 ,温度越高 ,LiMn2 O4的自放电越严重 ;贮存时间越长 ,LiMn2 O4的可逆容量损失越大 ,平均放电电压越低 ;高温下LiMn2 O4中Mn的溶解是造成比容量衰减的重要原因。通过掺杂微量元素的方法能有效地改善尖晶石LiMn2 O4的高温循环性能     

锂电池正极材料LiMn2O4的改性与循环寿命

对ＬｉＭｎ２Ｏ４进行改性可有效提高其循环寿命。其中合成掺杂ＬｉＭｎ２Ｏ４的解决循环性能下降的最有效手段。本文在探讨改性ＬｉＭｎ２Ｏ４的结构与其循环性能关系的基础上讨论了掺杂离子的选择标准。     

Gamma-irradiation effects on the electrical conductivity of pure and Co-doped MgAl2O4 spinel

The electrical conductivity of pure and Co-doped MgAl₂O₄ spinels was measured at 700–1100 K. The results of both pure and doped spinels were found to be fitted with an exponential expression with two different activation-energy parameters, in two ranges of temperature. The effect of -irradiation on the electrical conductivity of pure and doped spinels was also studied. The kinetic parameters of the isothermal annealing of the induced irradiation damages in the spinels were determined. All the results were found to be consistent with the ionic conduction which was suggested to be due to the motion of the cation vacancy.     

尖晶石LiMn_2O_4高温电化学容量衰减及改进

综述了高温下尖晶石ＬｉＭｎ２Ｏ４容量衰减的原因、机理研究和改进它的高温性能的方法以及目前的进展,且指出了可能的提高它的高温性能的途径。     

LiCoO2掺杂对锰酸锂结构和性能的影响

用固相反应合成了LiCoO2掺杂改性的LiMn2O4锂离子电池正极材料,优化了LiMn2O4的改性路径及制备条件.利用SEM、XRD对产物的结构进行了表征,并测试了产物的电化学性能.结果表明:所得产物均具有尖晶石型LiMn2O4结构.LiCoO2的掺入增加了尖晶石结构的稳定性,改善了尖晶石型LiMn2O4的充放电循环性能.     

锂离子电池正极材料LiMn_(2-2x)Sm_xSr_xO_4的合成及电化学性能

采用高温固相反应合成了一系列的LiMn2-2xSmxSrxO4正极材料(0≤x≤0.1);采用X射线衍射仪分析了合成产物的晶体结构;利用充放电试验测定了产物的电化学性能,利用电化学阻抗谱分析了产物的电化学循环机理.结果表明,所合成的LiMn2-2xSmxSrxO4(x=0,0.01,0.02,0.03,0.04,0.05)样品均保持尖晶石相,属于Fd3m空间群.LiMn1.9Sm0.05Sr0.05O4的电化学性能最佳,首次放电容量为96.8 mAh/g,在3.0~4.4 V区间内50次循环后容量保持率超过96%.与此同时,LiMn2O4和LiMn1.90Sm0.05Sr0.05O4的电极阻抗变化不同,进而影响其电化学性能.     

Hybrids of LiMn2O4 nanoparticles anchored on carbon nanotubes/graphene sheets as long-cycle-life cathode material for rechargeable hybrid aqueous batteries

Journal of Solid State Electrochemistry - A hybrid LiMn2O4-graphene-carbon nanotubes (LMO-GN-CNT) material is synthesized successfully by a facile hydrothermal method. The 15-nm-nanosized LiMn2O4...     

Nanofibers of LiMn2O4 by electrospinning

Through sol-gel processing and electrospinning technique, extrathin fibers of poly(vinyl alcohol) (PVA)/lithium chloride/manganese acetate composite fibers were prepared. After calcination of the above precursor fibers at 600 degrees C, the spinel lithium manganese oxide (LiMn2O4) nanofibers, with a diameter of 100-200 nm, were successfully obtained. The fibers were investigated by TG-DTA, XRD, FT-IR, and SEM, respectively. The results showed that the crystalline phase and morphology of the fibers were largely influenced by the calcination temperature.     

锂离子电池正极材料LiMn2O4的合成与晶体结构（英）

Spinel LiMn₂O₄ powders were prepared using two-step synthesis method consisting of solid-state reaction method and citrate modified sol-gel method. The effects of the calcination temperature and the Li/Mn ratio of raw materials were studied on the physicochemical and electrochemical properties of the spinel LiMn₂O₄ powders, such as crystallinity, lattice constant and density. The title compound was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Polycrystalline LiMn₂O₄ powers calcined at 750 ℃ were found to be composed of very uniformly-sized microcrystal with an average particle size of 300 nm. The improvement in electrochemical properties was mainly attributed to the process of re-grinding by absolute alcohol.