高倍率三元正极材料的制备及性能研究

发布时间：2018-05-18 03:32

本文选题：锂离子电池 + 正极材料　；参考：《西南石油大学》2017年硕士论文

【摘要】：三元正极材料 LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2、LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2 和 LiNi0.8Co0.1Mn0.1O_2 具有可逆比容量高、成本低等优点,应用前景广阔。然而,上述正极材料由于属于半导体材料,电子导电性差,导致其倍率性能及循环稳定性差,限制了其在实际生产中的应用。本论文以三元正极材料为研究对象,通过将其与石墨烯、碳纳米管构建的三维导电网络复合来提升其电化学性能,系统研究了复合材料的微观结构、电化学性能及两者之间的关联机制,并总结了复合材料电化学性能提升的机理。采用二维片状石墨烯(GNs)和一维管状碳纳米(CNTs)管构建的三维导电网络与LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2三元正极材料复合(LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2/GNs/CNTs)提升其电化学性能。复合材料中,GNs包覆在LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2表面,CNTs穿插于GNs和LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2的间隙,利于石墨烯与碳纳米管的协同效应,构筑高效三维导电网络,在最大程度上改善LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2的表面电子导电性,提升其倍率性能及循环稳定性。上述复合材料较之单一导电炭黑(SP)、GNs或CNTs与LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2复合制备的复合材料体现出了明显优异的电化学性能,LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2/SP、LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2/GNs、LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2/CNTs 和 LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2/GNs/CNTs 复合正极材料在1 C下分别具有156 mAhg-1、150 mAhg-1、142 mAhg-1,161 mAhg-1的初始放电比容量,经过1 C下循环50次分别保留了 56 mAhg-1 90 mAhg-1、75 mAhg-1,123 mAhg-1的放电比容量,容量保持率分别为:36%、60%、53%,76%。此外,论文还系统考察了不同类型的碳纳米管及石墨烯对复合材料电化学性能的影响,研究还表明:较细管径的多壁碳纳米管对提升三元正极材料LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2的电化学性能具有更好的效果;氧化石墨烯由于带有大量官能团,活性较高容易与电解液发生反应,不利于与三元正极材料电化学性能提升,还原氧化石墨烯具有较好的导电性和电化学惰性,与三元正极材料复合后能提升正极材料的倍率性能及循环稳定性;当石墨烯和碳纳米管的质量比为2:1时,复合材料具有最好的倍率性能和循环稳定性。论文还采用流变相法分别制备了 LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2和LiNi0.8Co0.1Mn0.1O_2三元正极材料,并系统研究了其与GNs、CNTs复合制备的复合材料的的电化学性能,研究结果表明,上述三元正极材料与GNs、CNTs共复合制备的复合材料体现出最优异的倍率性能及循环稳定性,且GNs和CNTs在复合材料中的最佳质量比仍为2:1。上述结果表明,利用 GNs 及 CNTs 与三元正极材料 LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2、LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2 和LiNi0.8Co01Mn0.1O_2共复合,通过GNs与CNTs的协同效应,均可以在复合材料中构建高效三维导电网络,有利于三元正极材料表面电子导电性的提升,从而促进其倍率性能及循环稳定性的提高。此外,GNs与CNTs在上述三种复合材料中的最佳质量比均为2:1,说明该方法在提升三元正极材料倍率性能及循环稳定性方面具有一定的普适性,亦具有潜在的商业应用价值。
[Abstract]:The three element positive material LiNi_ (1/3) Co_ (1/3) Mn_ (1/3) O_2, LiNi_ (0.5) Co_ (0.2) Mn_ (0.3) O_2 and LiNi0.8Co0.1Mn0.1O_2 have the advantages of high reversible specific capacity, low cost and low cost. However, the above cathode material is a semiconductor material, and the electrical conductivity is poor, resulting in poor multiplication and cycle stability. In this paper, the three element positive material was used as the research object. The electrochemical properties of the composites were improved by combining the three dimensional conductive network with graphene and carbon nanotubes to improve the electrochemical performance. The microstructure, electrochemical properties and the correlation mechanism of the composites were systematically studied, and the electrochemical properties of the composites were summarized. The three-dimensional conductive network constructed by two dimensional flake graphene (GNs) and one dimensional tubular carbon nanotube (CNTs) tube is used to improve the electrical properties of the LiNi_ (1/3) Co_ (1/3) Mn_ (1/3) O_2 three yuan cathode material (LiNi_ (1/3) Co_). Interspersed with the gap between GNs and LiNi_ (1/3) Co_ (1/3) Mn_ (1/3) O_2, it is beneficial to the synergistic effect of graphene and carbon nanotubes, to construct an efficient three-dimensional conductive network, and to improve the electronic conductivity of the LiNi_ (1/3) Co_ (1/3) Co_ (1/3) Co_ (1/3). The composite material prepared by CNTs and LiNi_ (1/3) Co_ (1/3) Mn_ (1/3) O_2 shows obvious excellent electrochemical performance. The initial discharge specific capacity of hg-1150 mAhg-1142 mAhg-1161 mAhg-1, after 1 C cycles, retained 56 mAhg-1 90 mAhg-1,75 mAhg-1123 mAhg-1 respectively, and the capacity retention rate was 36%, 60%, 53%, and 76%. respectively. The paper also systematically investigated the electrochemical properties of different types of carbon nanotubes and graphene. The results also show that the multi walled carbon nanotubes with smaller diameter have better effects on improving the electrochemical performance of the three element positive electrode material LiNi_ (1/3) Co_ (1/3) Mn_ (1/3) O_2, and the activity of graphene oxide is higher than that of the electrolyte, which is not conducive to the improvement of the electrochemical performance with the three element cathode material. The original graphene oxide has good conductivity and electrochemical inertia. It can improve the ratio and cyclic stability of the cathode material with the composite of three yuan positive material. When the mass ratio of graphene and carbon nanotube is 2:1, the composite has the best performance of multiplier and cyclic stability. The paper also uses rheological phase method to prepare LiN respectively. I_ (0.5) Co_ (0.2) Mn_ (0.2) Mn_ (0.3) O_2 and LiNi0.8Co0.1Mn0.1O_2 three yuan positive electrode materials, and systematically study the electrochemical properties of the composite prepared with GNs, CNTs composite. The results show that the composite materials prepared by the co compound of the three element positive electrode and GNs and CNTs show the most excellent multiplier and cyclic stability, and GNs and CNTs. The optimum mass ratio in the composite is still 2:1.. The results show that using GNs and CNTs, LiNi_ (1/3) Co_ (1/3) Mn_ (1/3) Mn_ (1/3) O_2, LiNi_ (0.5) Co_ (0.2) and co recombination, the efficient three-dimensional conductive network can be constructed in the composite by the synergistic effect. In addition, the optimum mass ratio of GNs and CNTs in the above three composite materials is 2:1, which shows that the method has a certain universality and potential in improving the ratio and cyclic stability of the three Yuan Zhengji material. The value of commercial application.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912

【参考文献】