锂离子电池正极材料层状锰酸锂的制备与性能研究

发布时间：2018-02-26 18:14

本文关键词： 锂离子电池层状锰酸锂 γ-MnOOH纳米棒水热法多形貌Mn_2O_3　出处：《天津大学》2014年硕士论文　论文类型：学位论文

【摘要】：正交型层状锰酸锂о-LiMnO2具有理论比容量高，价格低廉，原料丰富以及对环境无污染等优点，是一种极有潜力的锂离子电池正极材料。由于о-LiMnO2的电化学性能与其制备方法和形貌密切相关，且水热法易于控制所合成材料的结晶度、形貌及粒度分布等，，本文采用水热法，分别以γ-MnOOH纳米棒、α-Mn2O3纳米棒、Mn2O3-air和Mn2O3-N2为锰源，利用其不同形貌制备出多形貌的o-LiMnO2。并通过XRD、SEM、TEM和电化学测试等手段对其结构、形貌和电化学性能进行了研究。以KMnO4和CTAB为原料，采用水热法合成γ-MnOOH纳米棒的最佳制备条件为：反应温度为180℃，反应时间为12h，KMnO4和CTAB的摩尔比为3:1，升温速率为5℃·min-1。该纳米棒的平均直径约为200-500nm，长度约为5-10μm。进一步以γ-MnOOH纳米棒和LiOH·H2O为原料在水热条件下合成出o-LiMnO2纳米棒，其在2.0-4.5V电压范围内，0.1C倍率下的首次放电比容量高达167.1mAh·g-1，最高放电容量达到194.4mAh·g-1，循环30周后容量保持率为78.7%。但o-LiMnO2纳米棒经高温煅烧后呈颗粒状，电化学性能变差。以MnO2分别在空气、氮气气氛中煅烧生成的Mn2O3-air和Mn2O3-N2为前驱体制备出颗粒状的o-LiMnO2-air及o-LiMnO2-N2的电化学性能不同。其中，o-LiMnO2-air的电化学性能更好。以γ-MnOOH纳米棒在空气中高温煅烧后生成α-Mn2O3纳米棒为前驱体水热合成的o-LiMnO2-α纳米粒子的电化学性能较差。因此，前驱体的形貌对o-LiMnO2的形貌有重要影响，最终影响o-LiMnO2的电化学性能。
[Abstract]:Orthogonal type layered lithium manganese oxide -LiMnO2 has a high theoretical capacity, low cost, abundant raw materials and no pollution to the environment and other advantages, is a very promising cathode material for lithium ion batteries. The electrochemical performance of -LiMnO2 and a preparation method and morphology are closely related, and the hydrothermal method is easy to control the synthesis of materials the crystallinity, morphology and size distribution, using the hydrothermal method, respectively, gamma -MnOOH nanorods, alpha -Mn2O3 nanorods, Mn2O3-air and Mn2O3-N2 as the manganese source, the use of different morphologies were prepared by multi morphology of o-LiMnO2. and XRD, SEM, TEM and electrochemical testing methods on the structure, morphology and electrochemical performance of the study.
Taking KMnO4 and CTAB as raw materials, the optimum preparation conditions for the hydrothermal synthesis of gamma -MnOOH nanorods: reaction temperature is 180 DEG C, the reaction time is 12h, the molar ratio of KMnO4 and CTAB for 3:1, the heating rate is 5 DEG C, the min-1. nanorods with an average diameter of about 200-500nm, the length is about 5-10 M. further the gamma -MnOOH LiOH nanorods and H2O nanorods o-LiMnO2 was synthesized under hydrothermal conditions, in the voltage range of 2.0-4.5V, 0.1C ratio is lower than the first discharge capacity is as high as 167.1mAh - g-1, the highest discharge capacity reached 194.4mAh / g-1, 30 cycles Hourong volume ratio is 78.7%. but o-LiMnO2 nanorods by high temperature calcination after the granular, electrochemical performance becomes worse.
Using MnO2 in the air, calcined in nitrogen atmosphere to generate Mn2O3-air and Mn2O3-N2 as the precursor for the preparation of electrochemical performance of o-LiMnO2-air and o-LiMnO2-N2 in different granular. The electrochemical performance of o-LiMnO2-air is better. The gamma -MnOOH nanorods in the air after high-temperature calcination into a -Mn2O3 nanorods poor electrochemical performance of o-LiMnO2- alpha precursor nanoparticles synthesized in water heat. Therefore, has an important influence on the morphology of the precursor of o-LiMnO2, and ultimately affect the electrochemical performance of o-LiMnO2.

【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM912

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