锂离子电池高锰三元正极材料的富锂化研究

发布时间：2017-12-28 04:07

本文关键词：锂离子电池高锰三元正极材料的富锂化研究　出处：《河北工业大学》2015年硕士论文　论文类型：学位论文

【摘要】：本文研究高锰三元正极材料x Li2Mn O3·(1-x)Li Ni0.2Co0.2Mn0.6O2的富锂化,考察富锂量、合成方法、合成条件、预循环处理以及包覆和掺杂等改性方法对材料电化学性能的影响。采用XRD表征材料的晶体结构,采用SEM表征材料的形貌,采用恒流充放电测试、CV、EIS表征材料的电化学性能。考察不同富锂量,即x值(0.7、0.6、0.5和0.4)对材料性能的影响。研究表明:当x=0.5,即Li2Mn O3相和Li MO2相为1:1时得到的材料层状结构良好,阳离子混排程度较低,具有最高的比容量和最佳的循环稳定性。采用高温固相法,以过渡金属乙酸盐和Li2CO3为原料合成富锂正极材料0.5Li2Mn O3·0.5Li Ni0.2Co0.2Mn0.6O2,考察了煅烧温度(750、800、850、900℃)和煅烧时间(9、12、15、18 h)对材料性能的影响。800℃煅烧12 h得到的样品具有良好的层状结构;0.1 C充放电比容量分别为218、162.1 m Ah/g,库伦效率为74.36%;0.1 C循环5次容量保留率为106.9%;0.2 C循环10次容量保留率为93.93%。低压预循环处理能降低直接充电至高电位对材料结构的破坏,改善其倍率性能;Mg O包覆层能够抑制Li PF6分解产生的HF与电极材料反应,进而降低金属离子的溶解,改善材料的循环稳定性,最佳包覆量为2 wt.%。采用碳酸盐共沉淀法,以过渡金属硫酸盐溶液、Na2CO3溶液和氨水为起始反应物合成碳酸盐前驱体,考察了过渡金属离子浓度(0.5、1.0、1.5、2.0 mol/L)和沉淀溶液p H值(8.0、8.5、9.0)对材料性能的影响。研究表明:过渡金属盐溶液浓度为1.0 mol/L、沉淀溶液p H为8.5时制得的前驱体经混锂和高温煅烧后得到的样品具有良好的层状结构和较低的Ni2+、Li+阳离子混排度;0.1 C下首次充放电比容量分别为350.9、280.7 m Ah/g,库伦效率为79.99%;0.1 C循环5次容量保留率为91.92%;0.2 C循环10次容量保留率为99.71%。低压预循环处理在一定程度上提高了材料的比容量及其倍率性能;Na元素添加在材料中形成Na0.7Mn O2.05结构的新相,促进了Li+在材料中的扩散,提高了材料的倍率和循环性能。性能最佳的样品为Li1.11Na0.06Ni0.10Co0.10Mn0.63O2,2.0-4.8 V电压范围内0.2 C首次充放电比容量分别为359.2、277.9 m Ah/g,库伦效率为77.37%,0.5 C循环50次容量保留率为94.90%。
[Abstract]:In this paper, we studied the lithium enrichment of high manganese three pole cathode material x Li2Mn O3. (1-x) Li Ni0.2Co0.2Mn0.6O2. The effects of lithium content, synthesis method, synthesis conditions, pretreatment and coating and doping on the electrochemical properties of the material were investigated. The crystal structure of the material was characterized by XRD, and the morphology of the material was characterized by SEM. The electrochemical properties of the material were characterized by constant current charge discharge test, CV and EIS. The effects of different lithium content, namely x (0.7, 0.6, 0.5 and 0.4), on the properties of the materials were investigated. The research shows that when x=0.5, namely Li2Mn O3 phase and Li MO2 phase are 1:1, the material has good layered structure, low degree of cation mixing, and has the highest specific capacity and the best cycling stability. The lithium rich cathode material 0.5Li2Mn O3. 0.5Li Ni0.2Co0.2Mn0.6O2 was synthesized by using high-temperature solid phase method and transition metal acetate and Li2CO3 as raw material. The effects of calcination temperature (750, 800, 850, 900 degrees C) and calcination time (9, 12, 15, 18 h) on the properties of the material were investigated. The samples obtained by calcining 12 h at 800 degrees have good lamellar structure. The charge and discharge capacity of 0.1 C is 218 and 162.1 m Ah/g respectively, and the efficiency of Kulun is 74.36%. 0.1 C cycle 5 times capacity retention rate is 106.9%; 0.2 C cycle 10 time capacity retention rate is 10. Low pressure circulation treatment can decrease the damage of direct charging a high potential material structure, improve the rate performance; Mg O HF coated with electrode material Li PF6 decomposition can produce reaction inhibition layer, thereby reducing the dissolved metal ions, improving the cycling stability of materials, the best coating amount was 2 wt.%. Using co precipitation method, using transition metal sulfate solution, Na2CO3 solution and ammonia as the starting reactant synthesis of carbonate precursor, investigate the transition metal ion concentration (0.5, 1, 1.5, 2 mol/L) and P H precipitation solution (8, 8.5, 9) on the properties of materials. The research indicated that the transition metal salt solution concentration of 1 mol/L, P H as the precursor solution to precipitate 8.5 prepared by mixing lithium and calcined samples obtained with good layered structure and low Ni2+, Li+ cation mixing degree; 0.1 C the first charge discharge were 350.9, 280.7 m Ah/g the specific capacity, Kulun is 79.99%; 0.1 C 5 cycles the capacity retention rate was 91.92%; 0.2 C 10 cycles the capacity retention rate was 99.71%. Low pressure pre cycling treatment improves the specific capacity and rate performance of materials to a certain extent. Na element added to the material form a new phase of Na0.7Mn O2.05 structure, which promotes the diffusion of Li+ in materials, and improves the rate and cycle performance of materials. The best performance sample is Li1.11Na0.06Ni0.10Co0.10Mn0.63O2,2.0-4.8 V, which is 0.2 C within the voltage range. The first charge and discharge specific capacity is 359.2 and 277.9 m Ah/g, respectively. The efficiency of Kulun is 77.37%, 0.5 C cycle 50 times capacity retention rate is 94.90%.
【学位授予单位】：河北工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM912

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