富锂层状正极材料的合成及其性能表征

发布时间：2018-04-13 23:40

  本文选题：锂离子电池 + 正极材料　； 参考：《苏州大学》2016年硕士论文

【摘要】：近年来,随着经济的发展,锂离子电池被认为是混合电动汽车和电动汽车最具发展前景的一部分。到目前为止,许多国内外的研究人员致力于改善富锂层状正极材料的电化学性能,来提高锂离子电池的能量密度及功率密度,以满足大众对能源的需求。然而富锂层状正极材料在充放电过程中其首次不可逆容量损失大,倍率性能差,电压降等诸多问题也限制其进一步发展。因此,如何提升富锂层状正极材料的电化学性能已经成为当前研究的重点和难点。本文研究的主要内容(1)通过Zr元素取代Li_2MnO_3中Mn元素改善0.6Li[Li_(1/3)Mn_(2/3)]O_2·0.4LiMn_(5/12)Ni_(5/12)Co_(1/6)O_2材料循环性能和电压下降问题;(2)通过ZrO_2包覆0.6Li[Li_(1/3)Mn_(2/3)]O_2·0.4LiMn_(5/12)Ni_(5/12)Co_(1/6)O_2材料改善其循环性能。本论文工作内容如下:(1)采用喷雾干燥法制备一系列0.6Li[Li_(1/3)Mn_(2/3)(_(1-x))Zr_(2/3)x]O_2·0.4LiMn_(5/12)Ni_(5/12)Co_(1/6)O_2(0≤x≤10%)富锂层状正极材料。XRD、XPS、SEM结果表明Zr元素的引入并未改变材料的层状结构和晶体形貌。HRTEM结果表明Zr元素可以稳定材料的晶体结构。当Zr含量为4%时,材料的电化学性能最好。在2.0到4.8 V电压范围,充放电20 mA g~(-1)下,Zr4%的样品首次放电比容量达到261 mA h g~(-1),循环100圈后,容量保持率为84%,远高于未取代的样品。此外,Zr4%的样品循环100圈后呈现了0.16 V的最小电压降。(2)首先通过喷雾干燥法成功合成0.6Li[Li_(1/3)Mn_(2/3)]O_2·0.4LiMn_(5/12)Ni_(5/12)Co_(1/6)O_2(简称LNMCO),然后通过溶液法制备一系列ZrO_2包覆LNMCO复合材料。XRD、XPS和TEM分析结果表明ZrO_2仅仅堆积在LNMCO样品的表层,并没有改变LNMCO样品的晶体结构。在这些样品中,1.5%ZrO_2-LNMCO样品首圈放电比容量高达279.3mA h g~(-1),首圈库伦效率高达87.2%,不可逆容量损失仅有55.3 mA h g~(-1),当循环70圈以后,放电比容量为244.3 mA h g~(-1),电化学性能远远高于未包覆样品。但是在不同倍率充放电时,ZrO_2包覆LNMCO样品的倍率性能比较差,说明还需要进一步改进实验方法。
[Abstract]:In recent years, with the development of economy, lithium ion battery is considered as the most promising part of hybrid electric vehicle and electric vehicle.Up to now, many researchers at home and abroad have been working to improve the electrochemical performance of lithium-rich layered cathode materials to improve the energy density and power density of lithium-ion batteries, in order to meet the energy needs of the public.However, many problems such as the loss of the first irreversible capacity, the poor performance of the rate and the voltage drop of the lithium-rich layered cathode materials in charge and discharge process also limit their further development.Therefore, how to improve the electrochemical performance of lithium-rich layered cathode materials has become the focus and difficulty of current research.The main content of this paper is to improve the cyclic performance of 0.6Li by replacing mn in Li_2MnO_3 with Zr element. (1 / 3 / 3 / 3)) O2 0.4LiMn_(5/12)Ni_(5/12)Co_(1/6)O_2 material cycle performance and voltage drop problem are improved by ZrO_2 coated 0.6Li [1 / 3 / 3 / 0] O\ -2 0.4LiMn_(5/12)Ni_(5/12)Co_(1/6)O_2 material.The main work of this thesis is as follows: (1) A series of 0.6Li [Li_(1/3)Mn_(2/3)(_(1-x))Zr_(2/3)x] O _ 2 0.4LiMn_(5/12)Ni_(5/12)Co_(1/6)O_2(0 鈮，

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