富锂锰基锂离子正极材料制备与性能研究

发布时间：2018-01-12 07:30

  本文关键词：富锂锰基锂离子正极材料制备与性能研究　出处：《北京有色金属研究总院》2014年硕士论文　论文类型：学位论文

  更多相关文章： 锂离子电池 正极材料 富锂层状材料 控制结晶法 氢氧化物共沉淀

【摘要】：随着电子产品的功能不断增多,对锂离子电池提出了更高要求：质轻、长巡航时间、经久耐用、高安全性能和更低成本等。本文以高容量、低成本的富锂高锰锂离子电池正极材料为目标,重点开展了层状固溶体材料xLi2Mn03·(1-x)LiM02的制备及其电化学性能研究,主要完成了如下研究工作： 首先,设计了高容量层状富锂相材料xLi2Mn03·(1-x)LiMO2(M=Ni1/3Co1/3Mn1/3,0x1),即xLi[Li1/3Mn2/3]O2·(1-x)LiNi1/3Co1/3Mn1/3O2组成的体系固溶体材料,通过复合金属氢氧化物前驱体—高温固相转化法进行了探索性合成方法研究,利用XRD、 XPS、ICP、TEM、SEM等表征手段,研究了材料的化学组成、颗粒形貌、元素价态和晶体结构,采用扣式电池恒电流充放电测试方法研究了材料的电化学性能。 其次,采用连续共沉淀控制结晶晶体生长方法合成了上述所设计的固溶体材料相对应的5种镍钴锰氢氧化物前驱体,研究了EDTA和NH3·H2O二种配位剂对这些球形前驱体的微结构、元素价态与电化学性能的影响,选用EDTA为混合配位剂,以更简便可靠工艺合成出了组成可控、高密度、球形富锂锰基正极材料氢氧化物前驱体,取代了惯用的以NH3·H2O作为配位剂的合成思路。前驱体湿法合成最佳工艺参数：EDTA的合理用量在2.5g/L,反应温度50±2℃,反应体系pH控制在11.2，反应及晶体生长设计不宜超过50h,电机搅拌频率为38Hz。 再次,采用“两步煅烧”方式,在空气气氛中将氢氧化物前驱体进行高温锂化转化合成富锂高锰锂离子电池正极材料,通过采用均匀设计的方法,较方便快捷的获得了高温烧结条件,最佳烧结条件为：过锂量3%,预烧温度480℃,预烧时间5h,烧结温度900℃,烧结时间10小时。获得了较优异的富锂正极材料。 最后,对合成的系列富锂高锰材料进行了微结构及电化学性能表征。在晶体结构方面,该材料具有典型的层状六方a-NaFeO2结构(空间群为R3m)。在XRD图谱中可以观察到(006)/(012)和(108)/(110)峰有明显地分裂,表明该材料具有很好的二维层状结构。同时,从图中可以看出在200-25°之间出现一组较小的衍射峰,这是由于Li2Mn03的过渡金属层由Li/Mn=1/2的比例交替排列,具有超品格有序性。 测试了不同X值的xLi[Li1/3Mn2/3]O2·(1-x)LiMO2样品的电化学性能,x=0.6样品(即Li[Li0.20Mn0.54Ni0.13Co0.13O2)具有最高的首次放电比容量为252.3mAh/g。另通过不同干燥方式考察了前驱体价态对xLi[Li1/3Mn2/3]O2(1-x)LiMO2电化学性能的影响。
[Abstract]:With the increasing function of electronic products, the requirements of lithium-ion batteries are higher: light weight, long cruise time, durability, high safety performance and lower cost. The preparation and electrochemical properties of layered solid solution (xLi2Mn03 路1-xLiM02) for lithium-rich lithium-ion batteries with low cost were studied. The following research work has been completed: First of all, the high capacity layered lithium-rich phase material, xLi2Mn03 路1-xLiMO2 / Ni1 / 3Co1 / 3Mn1 / 3Mn1, or xLi, was designed. [Li1/3Mn2/3] O _ 2 路Li _ (1-x) LiNi1 / 3Mn1 / 3O2 solid solution material. The synthetic method of composite metal hydroxide precursor and high temperature solid phase transformation was studied, and characterized by means of XRD, XPSN ICP Tem SEM and so on. The chemical composition, particle morphology, elemental valence state and crystal structure of the materials were studied. The electrochemical properties of the materials were studied by means of constant current charge / discharge test of button batteries. Secondly, five kinds of nickel-cobalt-manganese hydroxide precursors corresponding to the above designed solid solution materials were synthesized by the method of continuous coprecipitation controlled crystal growth. The effects of EDTA and NH3 路H2O on the microstructure, valence state and electrochemical properties of these spherical precursors were studied. EDTA was selected as the mixed coordination agent. The hydroxide precursor with controllable composition, high density and spherical lithium-rich manganese base cathode material was synthesized by a more simple and reliable process. Instead of the conventional synthesis of NH3 路H2O as the coordination agent, the optimum technological parameter of the wet synthesis of precursor is 2.5 g / L, and the reaction temperature is 50 卤2 鈩，

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