富锂镍锰铬三元正极材料的制备与改性研究

发布时间：2018-03-06 10:17

  本文选题：Li1.016Cr0.103Mn0.464Ni0.356O2　切入点：溶胶凝胶法　出处：《河北工业大学》2015年硕士论文　论文类型：学位论文

【摘要】：本文以Li[Li1/3Mn2/3]O2-Li Cr O2-Li Ni1/2Mn1/2O2组成的体系为研究对象,采用溶胶凝胶法合成了五种三元富锂Li-Ni-Mn-Cr-O正极材料,研究了Cr与Mn+Ni的摩尔比(设Cr/Mn+Ni为x,x=0.44,0.38,0.29,0.21,0.15以下简称A~E)和水洗对材料的结构和电化学性能的影响,选择出较优的材料。然后对较优的材料进行条件优化,详细考察了反应温度、溶剂种类、柠檬酸与过渡金属比、煅烧温度和煅烧时间对材料电化学性能的影响,最后对材料进行了掺杂和包覆研究。通过XRD进行材料结构表征,SEM进行材料表面形貌表征和分析,ICP进行元素含量的测定,EIS、CV、恒流充放电测试进行电化学性能分析。过渡金属和柠檬酸摩尔比为1:1,调节p H=7,55℃合成A~E系列前驱体,400℃预烧4h,800℃煅烧12h,制备出的样品都具有层状结构,但有很强的吸湿性;经水洗处理未改变晶体结构,提高了该系列材料的电化学性能;实验证明,水洗溶出物为Li2Cr O4。其中,E样品水洗处理后(Li1.016Cr0.103Mn0.464Ni0.356O2)的电化学性能最好。继续对Li1.016Cr0.103Mn0.464Ni0.356O2优化,以水作溶剂、柠檬酸与过渡金属配比为1:1、85℃的反应温度、800℃下煅烧12h。合成的Li1.016Cr0.103Mn0.464Ni0.356O2具有典型的富锂层状的晶体结构。材料在2.0~4.8V,0.1C下首次放电比容量为190.2m Ah/g,经过20次充放电循环后,容量保持率为86.0%。利用溶胶凝胶法对Li1.016Cr0.103Mn0.464Ni0.356O2进行Co、Al掺杂,得到Li1.016Cr0.103Mn0.464-x Ni0.356Nx O2(x=0.01,0.02,0.03,0.04),讨论了不同掺杂量对Li1.016Cr0.103Mn0.464Ni0.356O2的晶体结构及电化学性能的影响。研究发现,1%Co掺杂的样品在小倍率下放电比容量略有提高。在0.1C和0.2C放电比容量分别达192.1m Ah/g、160.2m Ah/g;大倍率下循环稳定性显著提高,在0.5C和1.0C下,循环10次后,容量保持率分别为98.7%、102.0%。Al掺杂并没有改善材料的容量,但2%Al的掺杂的样品在0.5C下的稳定性能有了显著的提高。对Li1.016Cr0.103Mn0.464Ni0.356O2进行Al2O3和Mg O包覆研究。包覆量分别为1%、2%、3%、4%,其中,4%Al2O3包覆的材料在小倍率下其放电比容量虽然较纯样要低,但其0.5C和1C下放电容量定均比纯样要好,0.5C和1C放电容量分别为115.1m Ah/g和95.1m Ah/g。1%Mg O包覆的材料在大倍率下的放电容量均比纯样高,其在0.5C和1C放电容量分别为113.2和100.2m Ah/g。
[Abstract]:In this paper, five ternary lithium-rich Li-Ni-Mn-Cr-O cathode materials were synthesized by sol-gel method using the system of Li [Li1/3Mn2/3] O2-LiCrO2-Li Ni1/2Mn1/2O2. The effects of molar ratio of Cr and mn Ni (Cr/Mn Ni = 0.38U 0.38U 0.29 0.21 / 0.15) and washing on the structure and electrochemical properties of the materials were studied, and the better materials were selected. Then the optimum conditions were optimized and the reaction temperature was investigated in detail. Effects of solvents, ratio of citric acid to transition metal, calcination temperature and calcination time on the electrochemical properties of the materials, Finally, the doping and coating of the material were studied. The surface morphology of the material was characterized by XRD and the element content was determined by XRD. The electrochemical performance was analyzed by constant current charge-discharge test. The molar ratio of metal to citric acid is 1: 1, and the precursor of Agne series is synthesized at 55 鈩，

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