固相配位化学反应法合成锂离子电池正极材料LiMn₂O₄及其掺杂材料的研究

【作者】 陈立宝；

【导师】 贺跃辉；

【作者基本信息】 中南大学 ， 材料学， 2004， 硕士

【摘要】 本文采用固相配位化学反应法成功的合成出了超细尖晶石型LiMn₂O₄及其掺杂材料，从实验与理论相结合的角度系统的研究了其制备过程中的工艺参数、结构、形成机理和性能。 研究了原料的配比和焙烧温度对合成材料性能的影响，实验选择硝酸锂、醋酸锰和柠檬酸的摩尔比为1：2：3作为实验的原料配比，500～550℃为配位化合物前驱体的最佳焙烧温度。 550℃合成的材料物相纯净，结晶性好，锂含量为3.79％，与理论锂含量（3.84％）相当；粒度细小，粒度范围为0.06～0.5μm的粉末为82.10％，材料的比表面积为10.15m²／g，平均粒度为138.12nm；粉末颗粒为多孔结构，有一定程度的团聚；充电的两个电压平台约为4.05V和4.15V，放电的电压平台约为4.10V和3.95V，其首次放电比容量为124.2mAh／g；循环比容量稳定，随着循环次数的增加，比容量下降的比率减小，循环性能逐渐趋于稳定，十次循环后放电比容量为109.8mAh／g，为初始比容量的88.4％。 掺杂的LiM_xMn_2-xO₄（M=Ni，Co，Cr，Al，x=0.05，0.10，0.15，0.20）材料保持了尖晶石结构，形成了固溶体，离子半径小的掺杂元素离子M³⁺离子代替了Mn³⁺离子，减小了尖晶石结构的晶胞参数，稳定了结构；掺杂材料颗粒细小，颗粒内部存在有孔隙；掺杂材料随着掺杂浓度的提高，放电比容量降低；掺杂的LiM_0.10Mn_1.90O₄（M=Ni，Co，Cr，Al）材料结构稳定，循环电性能好，掺杂Co或Ni的材料的循环电性能最好，5次循环后LiCo_0.10Mn_1.90O₄材料和LiNi_0.10Mn_1.90O₄材料的放电比容量分别为119.5mAh／g和118.0mAh／g，是初始放电比容量的97.2％和96.3％。更多还原

【Abstract】 In this paper, ultrafmed spinel LiMn2O4 and the doped LiMn2O4 were synthesized by solid state coordination reaction. The preparing technological parameters, structure, formation mechanism and properties of LiMn2O4 and the doped LiMn2O4 were systematically studied and discussed.The ratios of primary materials and calcining temperature were studied systematically. The ratios of lithium nitrate, manganese acetate and citric acid are 1:2:3, and the optimum calcining temperature is 500~550℃.The spinel LiMn2O4 calcined at 550℃ attained pure phase and high crystllinity. The content of lithium is 3.79%(w/o), which is similar to the theory content (3.84%) of LiMn2O4 compound. The particle size of LiMn2O4 cathode prepared at 550℃ is fine, and the powder within particle size ranges of 0.06~0.5um amount 82.10% of the total. The specific surface area and the average particle size of the LiMn2O4 powder are 10.15m2/g and 138.12nm, respectively. The morphology of the powder show porous structure and are aggregative. The voltage plateaus of charge are 4.05V and 4.15V, and the discharge are 4.10V and 3.95V. The first discharge specific capacity is 124.2 mAh/g, and the material have good cyclability. The tenth discharge specific capacity is 109.8 mAh/g, which is 88.4% of the first discharge specific capacity.The LiMxMn2-xO4(M=Ni, Co, Cr, Al, x=0.05, 0.10, 0.15, 0.20) materials maintain spinel structure, in which the doped elements form solution. In the doped materials, the smaller M3+ substitut larger Mn3+, which decreases lattice parameter and stabilizes spinel structure. The particle size is fine and the morphology is porous. With the increasing of doping concentration, the discharge specific capacity decrease. The LiM0.10Mn1.90O4(M=Ni, Co, Cr, Al) materials have stable spinel structure and good cycleability. The Co or Ni doped materials have the best cycleability. The fifth discharge specific capacity of LiCo0.10Mn1.90O4 and LiNi0.10Mn1.90O4 materials are 119.5mAh/g and 118.0mAh/g, which were97.2% and 96.3% of the first discharge specific capacity, respectively.更多还原