过渡金属氧化物三维纳米结构的组装及其储锂性能研究
发布时间：2019-06-03 22:26
【摘要】：本论文主要针对传统过渡金属氧化物负极纳米颗粒循环稳定性差、堆积密度低和微米颗粒容量低、倍率差、循环差等关键科学问题,提出通过简易的水/溶剂热法组装具有三维纳米结构的过渡金属氧化物二次微米球型结构,合理调节组装工艺,实现对颗粒形貌、尺寸、孔结构和成分分布等性质的有效控制,成功开发了高容量、高倍率的针刺阵列型二元镍钴氧化物介孔微球负极材料和高倍率、长循环和高安全性的成分梯度富锰三元镍钴锰多孔微球正极材料。具体研究内容如下:(1)以尿素为沉淀剂和自模板成功组装得到阵列排布的针刺状NiCo(OH)2CO3纳米微球前驱体。经过适当调节空气下前驱体的分解温度,引入介孔结构,适当降低比表面积,同时在长大的一次颗粒中形成多相共存的相结构,电化学测试结果表明,在以上协同效应的作用下,两相共存的镍钴氧化物具有与纯相Ni1.5Co1.5O4相当的倍率性能但是循环性能获明显提高。(2)相比空气下退火得到的两相共存Ni1.5Co1.5O4,通过对针刺微球状前驱体NiCo(OH)2CO3在N2氛围下退火获得针刺阵列介孔微球型低价态纯相NiCoO_2同样展现出优异的倍率性能和相近循环性能,但是首圈不可逆容量降低了大约200 mAhg-1。(3)成功利用不同碳酸盐沉淀在弱酸性条件下的溶解度不同构建了具有富锰核心和三元壳层的成分梯度镍钴锰碳酸盐微球型前躯体,并深入讨论了抗坏血酸对碳酸盐前躯体和氧化物中间体的形貌、组分、晶体结构以及最终产物LiNi0.2Co0.3Mn0.5O_2正极材料的电化学性能的影响。研究结果表明,在制备前驱体过程中加入抗坏血酸有助于获得单分散性更好、二次颗粒更均匀细小、结构更致密和成分梯度更和缓的LiNi0.2Co0.3Mn0.5O_2介孔正极微球,最终获得具有优异倍率性能、循环性能、热稳定性及高堆积密度的富锰梯度层状三元氧化物正极材料。
[Abstract]:In this paper, the key scientific problems, such as poor cyclic stability, low stacking density, low micron particle capacity, poor doubling rate and cycle difference, are mainly discussed in the traditional transition metal oxide negative electrode nanoparticles, such as poor cyclic stability, low stacking density, low micron particle capacity, low doubling rate, poor cycle and so on. It is proposed that the secondary micron spherical structure of transition metal oxide with three dimensional nanostructure can be assembled by simple water / solvothermal method, and the assembly process can be adjusted reasonably to realize the effective control of particle morphology, size, pore structure and composition distribution. High capacity and high rate of acupuncture array binary nickel cobalt oxide mesoporous microspheres negative electrode materials and high rate, long cycle and high safety component gradient manganese rich ternary nickel cobalt manganese porous microspheres cathode materials were successfully developed. The specific research contents are as follows: (1) using urea as precipitant and self-template to successfully assemble the array arrangement of needle-like NiCo (OH) 2CO3 nanoparticles precursor. After properly adjusting the decomposition temperature of the precursor in the air, introducing the mesoporous structure, properly reducing the specific surface area, and forming the multiphase coexistence phase structure in the growing primary particles, the electrochemical test results show that, Under the above synergistic effect, the two-phase coexisting nickel-cobalt oxide has the same rate performance as pure phase Ni1.5Co1.5O4, but the cyclic performance is obviously improved. (2) compared with the two-phase coexisting Ni1.5Co1.5O4, obtained by air annealing The needle array mesoporous microsphere type pure phase NiCoO_2 was obtained by annealing the acupuncture microspherical precursor NiCo (OH) 2CO3 in N2 atmosphere. The pure phase NiCoO_2 also showed excellent doubling performance and similar cyclic performance. However, the irreversible capacity of the first cycle decreased by about 200 mAhg-1. (3) the composition gradient nickel cobalt manganese carbonate with rich manganese core and ternary shell was successfully constructed by using the different solubility of different carbonate precipitation under weak acid conditions. Salt microsphere precursor, The effects of ascorbic acid on the morphology, composition, crystal structure and electrochemical properties of the final product LiNi0.2Co0.3Mn0.5O_2 cathode materials were also discussed. The results show that the addition of ascorbic acid in the preparation of precursors is helpful to obtain LiNi0.2Co0.3Mn0.5O_2 mesoporous positive microspheres with better monodispersion, more uniform and fine secondary particles, denser structure and more gentle composition gradient. Finally, manganese-rich gradient layered ternary oxide cathode materials with excellent doubling performance, cyclic property, thermal stability and high stacking density were obtained.
【学位授予单位】：南京邮电大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1;TM912
本文编号：2492269
[Abstract]:In this paper, the key scientific problems, such as poor cyclic stability, low stacking density, low micron particle capacity, poor doubling rate and cycle difference, are mainly discussed in the traditional transition metal oxide negative electrode nanoparticles, such as poor cyclic stability, low stacking density, low micron particle capacity, low doubling rate, poor cycle and so on. It is proposed that the secondary micron spherical structure of transition metal oxide with three dimensional nanostructure can be assembled by simple water / solvothermal method, and the assembly process can be adjusted reasonably to realize the effective control of particle morphology, size, pore structure and composition distribution. High capacity and high rate of acupuncture array binary nickel cobalt oxide mesoporous microspheres negative electrode materials and high rate, long cycle and high safety component gradient manganese rich ternary nickel cobalt manganese porous microspheres cathode materials were successfully developed. The specific research contents are as follows: (1) using urea as precipitant and self-template to successfully assemble the array arrangement of needle-like NiCo (OH) 2CO3 nanoparticles precursor. After properly adjusting the decomposition temperature of the precursor in the air, introducing the mesoporous structure, properly reducing the specific surface area, and forming the multiphase coexistence phase structure in the growing primary particles, the electrochemical test results show that, Under the above synergistic effect, the two-phase coexisting nickel-cobalt oxide has the same rate performance as pure phase Ni1.5Co1.5O4, but the cyclic performance is obviously improved. (2) compared with the two-phase coexisting Ni1.5Co1.5O4, obtained by air annealing The needle array mesoporous microsphere type pure phase NiCoO_2 was obtained by annealing the acupuncture microspherical precursor NiCo (OH) 2CO3 in N2 atmosphere. The pure phase NiCoO_2 also showed excellent doubling performance and similar cyclic performance. However, the irreversible capacity of the first cycle decreased by about 200 mAhg-1. (3) the composition gradient nickel cobalt manganese carbonate with rich manganese core and ternary shell was successfully constructed by using the different solubility of different carbonate precipitation under weak acid conditions. Salt microsphere precursor, The effects of ascorbic acid on the morphology, composition, crystal structure and electrochemical properties of the final product LiNi0.2Co0.3Mn0.5O_2 cathode materials were also discussed. The results show that the addition of ascorbic acid in the preparation of precursors is helpful to obtain LiNi0.2Co0.3Mn0.5O_2 mesoporous positive microspheres with better monodispersion, more uniform and fine secondary particles, denser structure and more gentle composition gradient. Finally, manganese-rich gradient layered ternary oxide cathode materials with excellent doubling performance, cyclic property, thermal stability and high stacking density were obtained.
【学位授予单位】：南京邮电大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1;TM912
【参考文献】
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2 郑子山,张中太,唐子龙,沈万慈;锂离子二次电池最新进展及评述[J];化学世界;2004年05期
，本文编号：2492269
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