【作者】 阮艳莉；

【导师】 韩恩山；

【作者基本信息】 河北工业大学 ， 化学工艺， 2003， 硕士

【摘要】 本论文研究了二次锂离子电池的阴极材料——尖晶石型LiMn₂O₄的制备工艺条件以及不同的工艺条件对LiMn₂O₄的各种物理性能及晶体结构的影响。 论文采用了低温液相方法制备正尖晶石型锰的嵌锂氧化物正极材料。在同样的反应条件下，利用柠檬酸配合法制备出的正极材料具有颗粒均匀、组成均一的优点，尤其是改进工艺，采用无水乙醇二次研磨后连续焙烧出的纳米—亚微米量级的LiMn₂O₄结晶度高，颗粒适中，结构完美，有望成为优良的正极材料。 采用XRD、TEM、SEM、ICP等多种分析手段对合成的LiMn₂O₄进行了结构特征的表征。表明用改进的柠檬酸配合法可以合成出单相正尖晶石LiMn₂O₄，其典型的试样组成为LiMn₂O₄，晶格常数α=8.235，粒度大小为纳米级。此外利用TGA-DTA对其合成过程的动力学进行了研究。 研究了不同的工艺条件如溶液pH值、焙烧温度、焙烧时间、焙烧方式、Li/Mn的比值对产物结构的影响。发现溶液pH对合成产物的结构和性能有一定的影响，试验表明pH=6左右时，所制得的产物形貌均一、结构完整，具有较好的电化学性能；焙烧温度是将前体转化为单相LiMn₂O₄的关键，实验表明，经400℃预热，而后在750℃焙烧一定时间，可以得到单相的完整正尖晶石结构的LiMn₂O₄晶体；焙烧时间对产物颗粒有明显影响，焙烧时间过长，产物团聚现象严重；间断焙烧与连续焙烧这两种方式对制备出的产物晶型有不同的影响。 为了改善LiMn₂O₄的循环性能及在高温下容量衰减的问题，用Co、Cr、Ni、Cu等元素作为掺杂元素，采用改进后的工艺方法合成出LiM_xMn_2-xO₄（0.05≤x≤0.5），考察了掺杂元素对产物结构晶形的影响，优化出最佳掺杂量，分析了掺杂元素的作用。除此之外，还进行了LiMn₂O₄表面包裹的实验尝试，采用液相方法在自制的LiMn₂O₄表面包裹层状的LiCoO₂。 选取优化出的正极材料进行电化学性能测试，对锂离子的电化学性能与材料制备方面的关系作初步探索，并对实验现象进行定性的理论分析。更多还原

【Abstract】 The preparation and structure properties of spinel LiMn204 as a positive active material for lithium-ion battery were studied.The preparation of the positive electrode materials was done in the solution at low temperature. On the same conditions, the perfect spinel-structure LiMn2O4 can be synthesized using the citrate complex method, especially by improving technics, the nanometer and sub-micrometer sample was synthesized with fine crystallization, averaging crystal grain and composing, that is hopeful for electrode application.Different techniques, such as XRD, TEM, SEM, have been used to study the kinetics and examine the structure characteristics. The pure sample with spinel structure can be easily prepared by optimizing the processing parameters. The typical product is LiMniO4 with the cell constant a=8.235 and the powder size belongs to nanometer and sub-micrometer.The effects of different conditions on the phase structure have also been investigated. It’s obtained that pH=6.5 is a suited pH value for getting ideal product with good properties. The calcinate temperature is the key factors to transform the precursor to a pure product with spinel structure. Calcinate time can obviously influence the size of the sample, the longer of the calcinate time, the more severe of the conglomeration. And the continuous and discontinuous calcinate manners have different influences on the structure of the sample.For improving the cycling property and the volume fading at high temperature, LiMxMn2-xO4 with doping element Co CR Ni Cu (0.05<x<0.5), respectively, were synthesized by amelioratived technics. The influence of doping has been investigated. In addition of that, an attempt to colt LiMn2O4 with LiCoO2 in solution has been developed.Electrochemical techniques have been used to study the relationships between the synthesis and the electrochemical property of the positive electrode materials. The theoretical analysis for the experimental phenomena has been discussed.更多还原