尖晶石锰酸锂的制备与改性研究

发布时间：2019-05-05 17:33

【摘要】：LiMn2O4具有四面体和八面体共同构成的三维隧道结构，具有良好的大电流放电性能等优势；但在充放电循环中其结构易被破坏。本研究，，分别利用构建特殊结构和掺杂的方法，对尖晶石锰酸锂进行了改性，以提高材料的循环性能。以柠檬酸为络合剂，通过液相反应制得前驱体，然后分步烧结得到了纯相的尖晶石锰酸锂，并探究了实验工艺条件对材料性能的影响；利用聚丙烯酸接枝海绵为模板，制备了海绵状的锰酸锂，0.5C倍率下首次充放电电比容量分别为107mAh g-1和98mAh g-1，50次循环后容量保持率81.6%，循环得到改善。分别以Al3+和F-掺杂锰酸锂。当Al3+掺杂量为5%时材料循环性能最好，0.3C倍率下材料的首次充放电比容量分别为114.3mAh g-1和104.2mAh g-1，50次循环后容量保持率为89.5%。实验发现掺杂F-并不能改善锰酸锂的循环性能。通过进一步Al3+和F-的混合掺杂得到了循环性能稳定的锰酸锂材料。0.3C电流密度下，掺杂比例为Al7.5%、F2.5%的材料，首次充放电容量分别为121.1mAh g-1和112.2mAh g-1；50次循环以后，放电比容量为106.9mAh g-1，容量保持率为95.3%。掺杂后放电平台平均电压升高约0.08V，并由原来的双平台变为一个，放电变得平稳。通过特殊结构的构筑和掺杂，在一定程度上改善了材料的循环稳定性。
[Abstract]:LiMn2O4 has three-dimensional tunnel structure composed of tetrahedron and octahedron, which has good performance of high current discharge, but its structure is easily destroyed in charge-discharge cycle. In this study, special structure and doping methods were used to modify spinel lithium manganate in order to improve the cycling performance of the materials. The precursor was prepared by liquid phase reaction with citric acid as complexing agent, and then the pure phase lithium manganese manganate was obtained by step-by-step sintering, and the effect of experimental conditions on the properties of the material was investigated. The spongy lithium manganate was prepared by using polyacrylic acid grafted sponge as template. The initial charge / discharge specific capacity of lithium manganate at 0.5C ratio was 107mAh / g / 1 and 98mAh / g / 1, respectively. After 50 cycles, the capacity retention rate was 81.6%, and the cycle was improved. Al3 and F-doped lithium manganate were used respectively. When the content of Al3 is 5%, the cyclic performance of the material is the best. The initial charge-discharge specific capacity of the material at 0.3 C ratio is 114.3mAh / g / 1 and 104.2mAh / g / 1, respectively, and the capacity retention rate is 89.5% after 50 cycles. It was found that F-doping could not improve the cycle performance of lithium manganate. The cyclically stable lithium manganate material was obtained by further mixing of Al3 and F -. At 0.3C current density, the doping ratio of Al7.5%,F2.5% was the same as that of lithium manganate. The initial charge-discharge capacity was 121.1mAh g / 1 and 112.2mAh g / 1, respectively. After 50 cycles, the specific discharge capacity is 106.9mAh / g / 1 and the capacity retention rate is 95.3%. After doping, the average voltage of the discharge platform increased about 0.08 V, and changed from two platforms to one, and the discharge became stable. The cyclic stability of the material is improved to a certain extent by the construction and doping of special structure.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM912.9

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