镍钴锰三元锂离子电池正极材料的电化学性能的探究

发布时间：2018-03-04 09:10

  本文选题：LiNi_(0.6)Co_(0.2)Mn_(0.2)O_2　切入点：尿素均相沉淀　出处：《哈尔滨工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：由于高的能量密度以及成本优势,富Ni系镍钴锰三元层状氧化物LiNixCoyMnz02 (x0.5,文中简称为NCM),已成为主流的下一代锂离子电池正极材料。在实际应用中,为了获得更高的能量密度,最简单的办法是提高截止电压,但是富镍氧化物在高压工作时(4.3 V)会伴随着快速的容量衰减问题,较差的高压性能阻碍了富Ni三元层状氧化物的应用前景。为了获得较好性能的NCM三元材料,本文采用了三种方法进行LiNi0.6Co0.2Mn0.202(文中简称为NCM622)材料的制备,具体内容如下:第一部分采用共沉淀法成功制备出多孔形貌的LiNi0.6Co0.2Mn0.202材料。实验中探讨了陈化时间以及过锂量的影响。结果显示,过锂量为5%,陈化时间为12h时,阳离子的混排程度小和层状结构维持得较好。电化学性能测试显示由于维持了一种多孔的形貌,所以该材料的倍率性能较好,1 C (1 C=200mA/g)、2C、5C、10C 的比容量分别为 144mAh/g、130mAh/g、112 mAh/g、89mAh/g。第二部分采用尿素均相沉淀法制备出球状形貌的LiNi0.6Co0.2Mn0.202材料。结果显示,在本实验条件下,除醋酸类过渡金属盐受自组装的影响较弱之外,其余的阴离子在纯尿素体系中很难正确的沉淀出LiNi0.6Co0.2Mn0.202材料。通过调节溶液的pH值以及聚乙烯吡咯烷酮(PVP)辅助水热反应,可以生成正确LiNi0.6Co0.2Mn0.202材料,并且获得优化后的性能。pH=9时,在0.1 C、1 C、2C的倍率下的初始放电容量分别为:163 mAh/g、142mAh/g、102 mAh/g,循环50圈的能量保持率分别为:91%、93%、92%。160℃的聚乙烯吡咯烷酮(PVP)辅助水热法在1 C的倍率下的首次放电容量为134 mAh/g,50圈循环后的容量保持率为80%,比起纯尿素体系的68%得到了一定的提升。第三部分采用模版法制备出具有一定形貌的LiNi0.6Co0.2Mn0.202材料。结果显示,比起花状形貌的NiO模版,球状的模版的结构更加的稳定,本实验成功的合成了以球状NiO为模版的LiNi0.6Co0.2Mn0.202材料,经过高温烧结后依旧能够保持球形形貌,在0.1 C、1C以及2 C倍率下的初始放电比容量分别为:165 mAh/g、117 mAh/g以及93 mAh/g,循环50圈后的能量保持率分为:88%、84%以及82%。
[Abstract]:Because of its high energy density and cost advantage, Ni-rich nickel-cobalt-manganese ternary layered oxide (LiNixCoyMnz02 x 0.5) has become the mainstream cathode material for the next generation of lithium ion batteries. The easiest way to do this is to increase the cut-off voltage, but nickel rich oxides at high pressure work at 4.3 V) with a rapid capacity decay problem. In order to obtain better properties of NCM ternary materials, three methods were used to prepare LiNi0.6Co0.2Mn0.2022 (referred to as NCM622 in this paper). The main contents are as follows: in the first part, LiNi0.6Co0.2Mn0.202 materials with porous morphology were successfully prepared by coprecipitation. The effects of aging time and the amount of perlithium were discussed. The results showed that the amount of perlithium was 5 and the aging time was 12 hours. The results of electrochemical performance test show that because of maintaining a porous morphology, Therefore, the specific capacity of this material is 144mAh-gr 130mAh / gr 130mAh/ g / 10C, respectively. In the second part, the spherical LiNi0.6Co0.2Mn0.202 material is prepared by urea homogeneous precipitation method. The results show that, under the experimental conditions, the spherical morphology of the LiNi0.6Co0.2Mn0.202 material can be obtained by using urea homogeneous precipitation method. Except for the transition metal salts of acetic acid which are less affected by self-assembly, it is very difficult for the other anions to precipitate LiNi0.6Co0.2Mn0.202 materials correctly in the pure urea system. The hydrothermal reaction is assisted by adjusting the pH value of the solution and polyvinylpyrrolidone (PVP). The correct LiNi0.6Co0.2Mn0.202 material can be produced, and the optimized performance. Ph = 9:00, The initial discharge capacity at the rate of 0.1 C ~ (-1) C ~ (2 C) is 10: 163 mAh/ g ~ (142) mAh/ g ~ (10 ~ 2) mg / g, and the energy retention rate of 50 cycles is: 1 / 91 ~ 932 ~ 932 鈩，

本文编号：1565014