壳层组分及厚度对核壳NCM材料性能的影响研究

发布时间：2018-09-05 07:20

【摘要】：锂离子电池正极材料性能的好坏,在很大程度上制约着锂离子电池的使用寿命和安全性能,所以正极材料的研究是锂离子电池研究中的重中之重。具有三元层状结构的LiNixCoy Mn1-x-y O2,集LiNiO2、LiCoO2、LiMnO2三种材料的优点于一身,成本低廉、可逆容量较高、循环性能稳定,是一类非常有希望的材料之一。近几年,Yang-Kook Sun和Argonne实验室通过利用共沉淀法、高温固相法成功的制备出了一系列的核壳以及浓度梯度的LiNixCoy Mn1-x-y O2材料,经测试后发现,合成的核壳结构材料能够弥补非核壳结构材料的循环性能差、安全性能低的缺点。然而,Y.K.Sun和Argonne实验室并没有研究的是:不同壳层组分以及不同壳层厚度对核壳结构材料性能的影响,也没有对核壳结构材料与同成分下的非核壳结构材料进行对比性研究。因此,本论文依据LiNiO2-LiCoO2-LiMnO2三元相图,将已经商业化应用的LiNi0.5Co0.2Mn0.3O2和LiNi1/3Co1/3Mn1/3O2分别设计成同成分下的系列双核壳结构和系列单核壳结构材料,通过对比研究系列双核壳结构材料中壳层组分的不同,来分析壳层组分对材料性能的影响;通过对比系列单核壳结构材料中壳层厚度的不同,来分析壳层厚度对材料性能的影响。在本组实验中,设计核材料时,选择以高容量的LiNi0.8Co0.1Mn0.1O2作为核材料,以简单容易合成并且已经商业化应用的Li Ni1/3Co1/3Mn1/3O2为过渡壳层材料,分别以高稳定的Li Ni0.4Co0.2Mn0.4O2、LiNi0.45Co0.1Mn0.45O2、LiNi0.475Co0.05Mn0.475O2、LiNi0.5Mn0.5O2为壳材料,将Li Ni0.5Co0.2Mn0.3O2重新设计为双壳结构Li[(Ni0.8Co0.1Mn0.1)core(Ni1/3Co1/3Mn1/3)inter shell(Ni(1-x)/2CoxMn(1-x)/2)shell]O2(x=0、0.05、0.1、0.2)。在本实验中,首先用共沉淀的方法合成了相应的系列双核壳结构前驱体,然后将制备的前驱体与计量比的Li2CO3混合均匀(Li/M=1.05:1),然后在850°C下焙烧16 h,制备得到双壳结构的含锂氧化物。随后,对材料的组成、结构、形貌和电化学性能等进行了相应的测试与研究。比较相同成分下核壳结构材料中,不同壳层组分对核壳结构材料性能的影响。将LiNi1/3Co1/3Mn1/3O2设计成核壳结构Li{[NiyCo1-2yMny](1-x)}core{[Ni1/2Mn1/2]x}shell O2(0?x?0.5;6y+3x-6xy=2)。通过共沉淀法合成了具有核壳结构的前驱体{[NiyCo1-2yMny](1-x)}core{[Ni1/2Mn1/2]x}shell(OH)2,将洗涤、烘干、过筛后的前驱体与LiOH以一定的计量比(Li/M=1.05)混匀,经800°C高温煅烧后得到相应的含锂氧化物,然后对材料的组成、结构、形貌和电化学性能等进行了研究,研究核壳结构中不同壳层厚度对核壳结构材料性能的影响。通过对核壳结构LiNi0.5Co0.2Mn0.3O2和LiNi1/3Co1/3Mn1/3O2的研究和与同成分的非核壳结构材料对比发现,(a)核壳结构能够提高材料的循环性能以及热稳定性能;(b)在核壳结构材料中,随着壳层中Mn元素的增加,材料的循环性能以及热稳定性能会相应的提高;(c)随着壳层厚度的增加,材料的循环性能以及热稳定性能也有一定的提高。
[Abstract]:The performance of lithium-ion battery cathode material to a great extent restricts the service life and safety performance of lithium-ion battery, so the research of cathode material is the most important in the research of lithium-ion battery. LiNixCoy Mn1-x-y O _ 2 with ternary layered structure, which combines the advantages of three kinds of LiNiO2,LiCoO2,LiMnO2 materials, has the advantages of low cost, high reversible capacity and stable cyclic performance. It is one of the most promising materials. In recent years, the Yang-Kook Sun and Argonne laboratories successfully prepared a series of core-shell and concentration gradient LiNixCoy Mn1-x-y O _ 2 materials by means of co-precipitation and high-temperature solid-state method. The synthesized core-shell structure material can make up for the poor cycling performance and low safety performance of the non-core-shell structure material. However, the effect of different shell components and shell thickness on the properties of core-shell structure materials has not been studied in Y. K. Sun and Argonne laboratories, nor has a comparative study between core-shell structure materials and non-core-shell structural materials under the same composition been carried out. Therefore, according to the LiNiO2-LiCoO2-LiMnO2 ternary phase diagram, the commercial applications of LiNi0.5Co0.2Mn0.3O2 and LiNi1/3Co1/3Mn1/3O2 have been designed into a series of binocore structure and a series of monocore structure materials under the same composition, respectively. The effects of shell composition on material properties are analyzed by contrasting the difference of shell composition in a series of binuclear shell structure materials, and the difference of shell thickness in a series of monocore shell structure materials is compared. To analyze the influence of shell thickness on material properties. In the design of nuclear materials, high capacity LiNi0.8Co0.1Mn0.1O2 is chosen as nuclear material, Li Ni1/3Co1/3Mn1/3O2, which is simple and easy to synthesize and has been commercialized, is used as transitional shell material, and high stable Li Ni0.4Co0.2Mn0.4O2,LiNi0.45Co0.1Mn0.45O2,LiNi0.475Co0.05Mn0.475O2,LiNi0.5Mn0.5O2 is used as shell material, respectively. Li Ni0.5Co0.2Mn0.3O2 was redesigned as Li [(Ni0.8Co0.1Mn0.1) core (Ni1/3Co1/3Mn1/3) inter shell (Ni (1-x) / 2Co xMn (1-x) / r 2 shell] O 2 (x 0. 05) 0. 1 0. 2). In this experiment, a series of binuclear shell precursors were synthesized by coprecipitation method. Then the precursor was mixed with the stoichiometric Li2CO3 homogeneously (Li/M=1.05:1), and then calcined at 850 掳C for 16 h to prepare the lithium-containing oxide with double shell structure. Then, the composition, structure, morphology and electrochemical properties of the materials were tested and studied. The effects of different shell components on the properties of core-shell structure materials were compared under the same composition. The core-shell structure Li {[NiyCo1-2yMny] (1-x)} core {[Ni1/2Mn1/2] x} shell O _ 2 (0 ~ (10) x ~ (0.5) ~ (6) y 3x-6xy=2 was designed by LiNi1/3Co1/3Mn1/3O2. The precursor {[NiyCo1-2yMny] (1-x)} core {[Ni1/2Mn1/2] x} shell (OH) _ 2 with core-shell structure was synthesized by co-precipitation method. The precursor after washing, drying and sifting was mixed with LiOH at a certain measurement ratio (Li/M=1.05). After calcined at 800 掳C at high temperature, the corresponding lithium-containing oxides were obtained. The influence of different shell thickness on the properties of core-shell structure was studied. Through the study of the core-shell structure LiNi0.5Co0.2Mn0.3O2 and LiNi1/3Co1/3Mn1/3O2 and the comparison with the core-shell structure materials of the same composition, it is found that the core-shell structure of, (a) can improve the cycling performance of the material and the thermal stability of; (b) in the core-shell structure material increases with the increase of the Mn element in the shell layer. The cycle performance and thermal stability of the material will be improved with the increase of shell thickness, and the cycle performance and thermal stability of the material will also be improved with the increase of shell thickness.
【学位授予单位】：天津理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.4

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