节点文献
正极薄膜材料LiNi0.5Mn0.5O2的溶胶凝胶旋涂法制备及性能研究
Study on Sol-gel Spin Coating Preparation and Properties of LiNi0.5Mn0.5O2 Cathode Thin-films
【作者】 江润霞；
【导师】 肖亮；
【作者基本信息】 武汉理工大学 ， 无机化学， 2010， 硕士
【摘要】 层状结构LiNi0.5Mn0.5O2作为一种锂离子电池正极材料,具有结构稳定、比容量高、热安全性好、原料成本低等优点,被认为是极有研究价值的材料体系,但关于LiNi0.5Mn0.5O2薄膜材料的研究文献报道较少。本论文选取LiNi0.5Mn0.5O2薄膜材料作为研究体系,采用溶胶凝胶旋涂法制备。该工艺过程简单,与射频磁控溅射、脉冲激光沉积(PLD)等物理方法相比不需要昂贵的设备,制备成本较低,而且化学组分容易控制,便于规模生产。本论文综合文献报道,选取价廉易得的醋酸锂、醋酸锰和乙酰丙酮镍为原料,通过大量实验摸索出稳定、均匀的前躯体溶胶的配制方法。采用旋转涂膜技术,在Si基片、Pt/Ti/SiO2/Si基片和Pt基片上分别制备了LiNi0.5Mn0.5O2薄膜材料。主要讨论了溶胶凝胶旋涂法制备薄膜工艺中影响成膜质量和性能的各种因素：(1)前驱体溶液的配制,包括原料配比、溶液中总金属离子浓度以及成膜助剂浓度对成膜质量的影响等；(2)旋涂工艺,包括甩胶速度及时间的控制,,湿膜干燥工艺的确定；(3)高温退火方式,退火温度和退火升温速率对LiNi0.5Mn0.5O2薄膜的结构、形貌及电化学性能的影响。利用各种测试手段XRD,SEM,TG/DSC, ICP-AES, CV测试和电化学性能测试等,系统研究了原料配比、PVP的用量、干燥处理温度、退火温度及升温速率等对LiNi0.5Mn0.5O2薄膜的结构、形貌及电化学性能的影响。通过优化工艺参数,我们制得了表面结晶均匀、致密、无裂痕的LiNi0.5Mn0.5O2薄膜材料,具有良好的电化学性能。研究表明最佳产物的制备条件为：醋酸锂+乙酰丙酮镍+醋酸锰+冰醋酸+异丙醇+水,以PVP为成膜助剂,其中Li/(Mn+Ni)=1.20,金属离子总浓度0.66mol/L为宜,PVP最佳浓度为0.5mol/L;旋涂工艺转速为3000rpm,时间30s,重复旋涂五次得到所需厚度薄膜；当干燥温度为450℃,并在700℃(控制一定的升温速率)退火30min得到的LiNi0.5Mn0.5O2薄膜材料结构形貌及电化学性能良好。XRD结果表明,最佳条件下制备的LiNi0.5Mn0.5O2薄膜材料具有纯相的层状结构,ICP分析薄膜的化学组成为Li1.01Ni0.5Mn0.5O2,在电压范围2.5V-4.5V以20μA/cm2的电流充放电时,首次放电容量为92.28μAh/cm2μm,循环50次后为73.68μAh/cm2μm,容量保持率约为80%。
【Abstract】 LiNi0.5Mn0.5O2 as a layered structure of lithium-ion battery cathode materials with stable structure, high specific capacity, heat safety, low cost of raw materials, is considered the most research value of the material system, but on the LiNi0.5Mn0.5O2 thin film materials reported less. The paper selected as a research system LiNi0.5Mn0.5O2 thin films, sol-gel spin coating method. The process is simple, and RF magnetron sputtering, pulsed laser deposition (PLD) compared with other physical methods do not need expensive equipment, preparation costs are lower, and the chemical composition easy to control, easy to scale production.The comprehensive study reported in the literature, select the cheap and easily obtained lithium acetate, manganese acetate and nickel acetylacetone raw material by a large number of experiments to explore the stability of a uniform method for the preparation of precursor sol. By spin coating techniques, in Si substrate, Pt/Ti/SiO2/Si substrate and the Pt substrate LiNi0.5Mn0.5O2 films were prepared. Mainly discussed the preparation of sol-gel films by spin-coating of film quality and performance in a variety of factors:(1) precursor solution preparation, including raw material ratio, the total metal ion concentration in solution and the concentration of film-forming additives on the film quality; (2) spin-coating process, including the rejection of plastic speed and time control, the determination of wet film drying process; (3) high temperature annealing method, annealing temperature on the structure of the films LiNi0.5Mn0.5O2, shape and the morphology and electrochemical properties. Using a variety of testing methods XRD, SEM, TG/DSC, ICP, CV and electrochemical performance testing, test, system of raw material ratio, PVP amount, annealing temperature and film preparation parameters on the structure of LiNi0.5Mn0.5O2, morphology and electrochemical properties. By optimizing the process parameters, we got the surface crystallization of the system uniform and compact film material LiNi0.5Mn0.5O2 no cracks, with good electrochemical performance.Studies show that the best system for the precursor solution:lithium acetate+nickel acetylacetone+manganese acetate+water+acetic acid to PVP as a film-forming additives, including Li/(Mn+Ni)=1.20, metal ions total concentration of 0.66 mol/L is appropriate, PVP optimal concentration of 0.5 mol/L; spin-coating process speed in 3000rpm, time 30s, five are required to repeat the spin-coated film thickness; when the drying temperature was 450℃, and 700℃(heating rate control certain) 30min annealing structure of thin films obtained LiNi0.5Mn0.5O2 morphology and electrochemical performance is good. XRD results show that under the best conditions LiNi0.5Mn0.5O2 thin films prepared with pure phase of layered structure, ICP analysis of the chemical composition of thin films Li1.01Ni0.5Mn0.5O2, in the voltage range of 2.5V-4.5V to 20μA/cm2 of the current charge and discharge, the initial discharge capacity of 92.28/μAh/cm2μm, after 50 cycles 73.68μAh/cm2μm, the capacity retention rate of about 80%.