钴基三元过渡金属氧化物锂离子电池负极材料的制备及电化学性能研究
发布时间：2018-08-23 21:04
【摘要】：锂离子电池具有高能量密度、长循环寿命和价格低廉等优点,因此在各个领域被广泛应用。但是,当前常用的锂离子电池负极材料主要是石墨类材料,由于其理论容量较低,不能满足人们日益增长的需求。因此,寻找新型具有高充放电容量和较好循环性能的负极材料至关重要。相较于石墨类负极材料,三元过渡金属氧化物由于具有高的理论比容量,受到了人们的广泛研究。本论文以提高锂离子电池电化学性能为目的,主要以三元过渡金属氧化物为中心,通过对材料纳米化、构筑空心结构和复合这些方法来提高其电化学性能,具体的研究为如下三个方面:1.通过一步水热法成功合成出了多孔空心CuCo_2O_4纳米微球和空心MgCo_2O_4纳米微球,研究了构筑空心结构对其作为锂离子电池负极材料的电化学性能影响。与实心CuCo_2O_4纳米微球比较,多孔空心CuCo_2O_4纳米微球表现出了优异的电化学性能,在电流密度为0.1 Ag~(-1)时,多孔空心CuCo_2O_4纳米微球经过150圈的循环后其可逆容量仍然保持在930 mAh g~(-1),对于实心CuCo_2O_4纳米微球而言仅仅经过70圈的循环后已经衰减到了430 mAh g~(-1)。该结果表明,空心结构的构筑使其储锂性能有了明显的提高,主要原因是空心结构具有较大的比表面积,有助于增大电解液与电极的接触面积同时可以提供更多的存储锂的电化学活性位点。2.利用水热法原位复合的方法合成了 CuCo_2O_4/rGO复合材料。相较于单纯的CuCo_2O_4,与石墨烯进行复合后的电极材料表现出了更好的循环和倍率性能。在电流密度为0.5 Ag~(-1)时,CuCo_2O_4/rGO复合材料经过200圈循环以后其容量仍然可以保持在900 mAh g~(-1),其优异的电化学性能得益于石墨烯的引入可以缓解材料在充放电过程中的体积膨胀同时也可以克服纳米粒子的团聚。3.以空心碳微球为模板,然后通过水热法成功合成出了空心HC@NiCo_2O_4复合材料。经过热重分析,所合成的复合材料中的碳含量为23.1%,独特的结构使其作为锂离子电池负极材料的时候展现出了优越的电性能,在100圈循环以后其放电比容量仍然可以保持在810 mAhg~(-1)(0.5 Ag~(-1))。材料呈现出空心纳米花状的结构,在充放电的时候有助于电解液与电极材料的接触,可以形成较大的固液接触面,这样可以缩短电子和离子的传输路径,进而提高了其电化学性能。
[Abstract]:Lithium ion batteries are widely used in many fields because of their high energy density, long cycle life and low cost. However, graphite is the main anode material of lithium ion battery, which can not meet the increasing demand due to its low theoretical capacity. Therefore, it is very important to find new negative materials with high charge and discharge capacity and good cycling performance. Compared with graphite anode materials, ternary transition metal oxides have been widely studied because of their high theoretical specific capacity. In order to improve the electrochemical performance of lithium-ion batteries, the electrochemical properties of the lithium-ion batteries were improved by nanocrystalline materials, hollow structures and composite methods, focusing on the ternary transition metal oxides. The specific research is as follows: 1. Porous hollow CuCo_2O_4 nanospheres and hollow MgCo_2O_4 nanospheres were successfully synthesized by one-step hydrothermal method. The effect of hollow structure on the electrochemical properties of hollow CuCo_2O_4 nanospheres as anode materials for lithium ion batteries was studied. Compared with solid CuCo_2O_4 nanospheres, porous hollow CuCo_2O_4 nanospheres exhibit excellent electrochemical properties. When the current density is 0.1 Ag~ (-1), the porous hollow CuCo_2O_4 nanospheres exhibit excellent electrochemical properties. The reversible capacity of porous hollow CuCo_2O_4 nanospheres remains at 930 mAh g ~ (-1) after 150 cycles. For solid CuCo_2O_4 nanospheres, it has been attenuated to 430 mAh g ~ (-1) only after 70 cycles. The results show that the structure of hollow structure has greatly improved the lithium storage performance, which is mainly due to the large specific surface area of hollow structure. It can increase the contact area between electrolyte and electrode and provide more electrochemical active sites of lithium storage. CuCo_2O_4/rGO composites were synthesized by hydrothermal in-situ recombination. Compared with the composite of CuCo_2O_4, and graphene, the electrode material showed better cycling and rate performance. When the current density is 0. 5 Ag~ (-1), the volume of cuCo _ 2O _ 4 / r go composite can still be maintained at 900 mAh g ~ (-1) after a 200th cycle. Its excellent electrochemical performance is due to the introduction of graphene, which can alleviate the volume expansion of the material during charging and discharging. Expansion can also overcome the agglomeration of nanoparticles. Hollow HC@NiCo_2O_4 composites were successfully synthesized by hydrothermal method using hollow carbon microspheres as template. The thermogravimetric analysis shows that the carbon content of the composite is 23.1.The unique structure makes it exhibit excellent electrical properties when it is used as cathode material for lithium ion battery. The specific discharge capacity of the composite can be maintained at 810 mAhg~ (-1) (0.5 Ag~ (-1).) after 100th cycle. The material shows hollow nanoscale structure, which is helpful to the contact between electrolyte and electrode material during charge and discharge, and can form a large solid-liquid contact surface, which can shorten the transmission path of electron and ion. Furthermore, the electrochemical performance was improved.
【学位授予单位】：西北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1;TM912
本文编号：2199911
[Abstract]:Lithium ion batteries are widely used in many fields because of their high energy density, long cycle life and low cost. However, graphite is the main anode material of lithium ion battery, which can not meet the increasing demand due to its low theoretical capacity. Therefore, it is very important to find new negative materials with high charge and discharge capacity and good cycling performance. Compared with graphite anode materials, ternary transition metal oxides have been widely studied because of their high theoretical specific capacity. In order to improve the electrochemical performance of lithium-ion batteries, the electrochemical properties of the lithium-ion batteries were improved by nanocrystalline materials, hollow structures and composite methods, focusing on the ternary transition metal oxides. The specific research is as follows: 1. Porous hollow CuCo_2O_4 nanospheres and hollow MgCo_2O_4 nanospheres were successfully synthesized by one-step hydrothermal method. The effect of hollow structure on the electrochemical properties of hollow CuCo_2O_4 nanospheres as anode materials for lithium ion batteries was studied. Compared with solid CuCo_2O_4 nanospheres, porous hollow CuCo_2O_4 nanospheres exhibit excellent electrochemical properties. When the current density is 0.1 Ag~ (-1), the porous hollow CuCo_2O_4 nanospheres exhibit excellent electrochemical properties. The reversible capacity of porous hollow CuCo_2O_4 nanospheres remains at 930 mAh g ~ (-1) after 150 cycles. For solid CuCo_2O_4 nanospheres, it has been attenuated to 430 mAh g ~ (-1) only after 70 cycles. The results show that the structure of hollow structure has greatly improved the lithium storage performance, which is mainly due to the large specific surface area of hollow structure. It can increase the contact area between electrolyte and electrode and provide more electrochemical active sites of lithium storage. CuCo_2O_4/rGO composites were synthesized by hydrothermal in-situ recombination. Compared with the composite of CuCo_2O_4, and graphene, the electrode material showed better cycling and rate performance. When the current density is 0. 5 Ag~ (-1), the volume of cuCo _ 2O _ 4 / r go composite can still be maintained at 900 mAh g ~ (-1) after a 200th cycle. Its excellent electrochemical performance is due to the introduction of graphene, which can alleviate the volume expansion of the material during charging and discharging. Expansion can also overcome the agglomeration of nanoparticles. Hollow HC@NiCo_2O_4 composites were successfully synthesized by hydrothermal method using hollow carbon microspheres as template. The thermogravimetric analysis shows that the carbon content of the composite is 23.1.The unique structure makes it exhibit excellent electrical properties when it is used as cathode material for lithium ion battery. The specific discharge capacity of the composite can be maintained at 810 mAhg~ (-1) (0.5 Ag~ (-1).) after 100th cycle. The material shows hollow nanoscale structure, which is helpful to the contact between electrolyte and electrode material during charge and discharge, and can form a large solid-liquid contact surface, which can shorten the transmission path of electron and ion. Furthermore, the electrochemical performance was improved.
【学位授予单位】：西北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1;TM912
【参考文献】
相关期刊论文 前4条
1 闫时建,田文怀,其鲁;锂离子电池正极材料钴酸锂近期研制进展[J];兵器材料科学与工程;2005年01期
2 王金才,李峰,刘畅,李洪锡;锂离子电池碳负极材料的研究现状与发展[J];腐蚀科学与防护技术;2004年05期
3 施思齐,欧阳楚英,王兆翔;锂离子电池中的物理问题及其研究进展[J];物理;2004年03期
4 邓敏超;锂离子电池负极材料研究进展[J];娄底师专学报;2003年02期
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