【作者】 邓艳波；

【导师】 唐致远；

【作者基本信息】 天津大学 ， 应用化学， 2006， 硕士

【摘要】 层状镍酸锂是一种容量极高的锂离子电池正极材料,本文从镍酸锂出发,合成出了三种高容量锂离子电池正极材料LiMxNi_0.8-xCo_0.2O₂、LiNi_1/3Mn_1/3Co_1/3O₂、LiNi_1/2Mn_1/2O₂,分别研究了三种材料的性能,为开发低成本、高性能的新型锂离子电池正极材料做出了有益探索。采用高温固相法合成了LiMxNi_0.8-xCo_0.2O₂（M=Mg、Al、La,x=0～0.05）,氧气氛,800℃烧结12小时,研究了实验范围内不同x值时材料的电化学性能及结构,发现当x值分别为0.05,0.05和0.01时,材料的前20次循环性能最好,其中LiAl_0.02Ni_0.78Co_0.2O₂与LiAl_0.05Ni_0.75Co_0.2O₂的电化学性能差别不是很明显。XRD图显示上述三种材料均为层状结构。采用共沉淀合成前驱使体的方法制备了LiNi_1/3Mn_1/3Co_1/3O₂正极材料,研究表明,合成前驱体控制PH=11±0.2,反应温度控制在50℃左右,烧结温度1000℃,保温20小时,Li/（Ni+Mn+Co）=1.15时,合成出的材料电化学性能最优。LiNi_1/3Mn_1/3Co_1/3O₂材料分别在2.5～4.3,2.5～4.5,2.5～4.7电压范围下进行充放电,以1C=180 mAh/g为基准,设置电流0.1C,初始放电容量分别为172.9 mAh/g、177.1 mAh/g、200.7 mAh/g,随电压的升高而增大;首次充放电效率分别为95.2%、88.6%、84.9%,随电压的升高而降低,循环性能也呈现此规律。,以LiNi_1/3Mn_1/3Co_1/3O₂为正极材料的实验电池在0.2C、0.5C、1C条件下充放电,首次放电容量分别为169.3 mAh·g-1,143.1 mAh·g-1,133.4 mAh·g-1,30次循环后容量保持率均在92%以上。XRD结果显示LiNi_1/3Mn_1/3Co_1/3O₂材料为良好的层状固熔体,R=1.38,阳离子混排程度低。交流阻抗谱表明该材料循环过程中容量损失的主要原因是正极/溶液界面电阻的增加。循环伏安数据说明LiNi_1/3Mn_1/3Co_1/3O₂充放过程主要发生两对氧化还原反应。DSC结果显示LiNi_1/3Mn_1/3Co_1/3O₂材料的放热温度范围比钴酸锂及镍酸锂均宽,热稳定性较好。采用共沉淀合成前驱体方法制备了LiNi_1/2Mn_1/2O₂正极材料,材料在2.5～4.3,2.5～4.5,2.5～4.7电压范围内0.1C充放电,首次放电容量分别为166.9mAh/g、180.4mAh/g、191.9mAh/g,首次充放电效率分别为90.7%、86.4%、82.1%,循环性能随电压的升高而下降,XRD图谱显示该材料为层状固溶体结构,但R=0.79,小于1.2,说明样品的阳离子混排程度较为剧烈。更多还原

【Abstract】 Lithium nickel oxides is a high capacity cathode material for lithium-ion batteries, we synthesized three cathode materials for lithium-ion batteries, LiMxNi_0.8-xCo_0.2O₂,LiNi_1/3Mn_1/3Co_1/3O₂ ,LiNi_1/2Mn_1/2O₂,and studied the performance of those materials, this article is assistance to cathode material with low cost but high power.A series of layer compounds LiMxNi_0.8-xCo_0.2O₂（M=Mg, Al, La, x=0～0.05） were synthesized by solid state reaction with high temperature, the oxygen was needed in this reaction, the temperature was controlled with keeping 12 hours at 800℃.the good cycle performance were got as x=0.05,0.05,0.01 .LiAl_0.02Ni_0.78Co_0.2O₂ and LiAl_0.05Ni_0.75Co_0.2O₂ were not clearly different. XRD pattern of LiMxNi_0.8-xCo_0.2O₂（M=Mg, Al, La） indicated these materials were layer structure.The co-precipitation technology was employed to synthesize the precursor of Ni、Co and Mn hydroxides ,With the precursor mixed with LiOH·H2O in solid state then sintered in air , LiNi_1/3Mn_1/3Co_1/3O₂ can be obtained as cathode material for lithium-ion batteries. Experiments of electrochemistry performance and characteristics of XRD, SEM were carried out. The lattice structure of the material was anα-NaFeO2 layered, hexagonal （space group R3m） . Initial discharge capacities of 173,177,200 mAh·g-1 were respectively obtained in the range of 2.5～4.3,2.5～4.3,2.5～4.7V（current density 18 mA·g-1）,and its electrochemical stability descended with the increase of the charge-discharge voltage.The material was charge-discharge at different current density 0.36mA·g-1（0.2C）、0.90 mA·g-1（0.5C）、180 mA·g-1（1C）, the results showed that the material was suited to discharge at larger current. XRD pattern of LiNi_1/3Mn_1/3Co_1/3O₂ indicated that the compound had a good layer structure, R=I003/I104=1.38, the cation mixed degree was lower. We could find that the dominating reason of capacity fading was possibly the resistance increasing of the cathode/solution interface from the EIS pattern. The CV pattern indicated that the material took place two dominating redox reaction. The result of DSC showed that LiNi_1/3Mn_1/3Co_1/3O₂ had a wider radiative apex than LiCoO2 and LiNiO2, and its hot stabilization was better.The precursor of LiNi_1/2Mn_1/2O₂ was synthesized by the co-precipitation technology . Initial discharge capacities of 166.9mAh/g、180.4mAh/g、191.9mAh/g were respectively obtained in the range of 2.5～4.3,2.5～4.3,2.5～4.7V（0.1C）,and its electrochemical stability descended with the increase of the charge-discharge voltage.XRD pattern of LiNi_1/2Mn_1/2O₂ indicated that the compound had a good layer structure, R=I003/I104=0.79, the cation mixed degree was acute.更多还原