【作者】 伍斌；

【导师】 胡国荣；

【作者基本信息】 中南大学 ， 材料冶金， 2011， 硕士

【摘要】 由于具有高容量,低成本等优势,高镍系正极材料是一种极具应用前景的锂离子电池材料。然而,目前的方法合成的材料还存在诸多不足,其性能有待改进。论文针对共沉淀法合成LiNi0.8Co0.15Al0.0502工艺中的关键问题展开系统研究,探索了一种高容量正极材料的合成工艺。该工艺操作简单,成本低,有助于实现LiNi0.8Co0.15Al0.0502材料的产业化。论文通过控制结晶法合成了球形前驱体。配锂盐,热处理合成了LiNi0.8Coo.15Al0.05O2材料。考察了预处理温度、预处理时间、焙烧温度等合成条件对材料的结构、形貌及电化学性能的影响。得到了优化的合成条件：前驱体在750。C下高温预处理4h后,加入理论锂用量105%的锂盐,在氧气气氛下750℃恒温煅烧15h。优化条件下合成的材料表现出了优异的电化学性能。0.1C,0.2C和2.5 C充放电倍率下,材料的放电比容量分别为203.2 mAh·g-1,192.4 mAh·g-1和146.8 mAh·g1。0.2C和2.5C充放电倍率下30次循环后,容量保持率分别为93.7%和93.3%。考察了不同包覆工艺及不同包覆组分对LiNi0.8Co0.15Al0.05O2材料电化学性能的影响。沉淀法包覆LiCoO2的材料表现出最好的电化学性能。55℃、0.2C充放电倍率下,包覆钻量为1.2wt%材料首次放电比容量为191.7 mAh·g1,经过38次充放电循环后,容量保持率为93.7%。采用溶胶-凝胶法合成了Si02包覆LiNi0.8Coo.15Al0.05O2材料,其中,包覆1.0wt% Si02的材料具有最高的初始容量和最好的循环性能。55℃,O.1C和0.2C充放电倍率下,材料的首次放电比容量分别为199.1 mAh·g1和191.9 mAh·g-1,0.2C充放电倍率下循环30次,容量保持率为94.6%。更多还原

【Abstract】 With high capacity and low cost, rich nicklic cathode are very intractive materials for lithium ion battery. However, the performance of the materials prepared by present synthetic methods is not good enough for lithium-ion battery. In the paper, the key isssues of LiNio.8Coo.15Al0.05O2 prepared by co-precipitation method were systematically studied, we has explored a new mothed for preparing LiNio.8Co0.15Al0.05O2 cathode material. The mothed is simple and the material shows good performance. It is helpful in preparing rich nicklic cathode material in large scale. To avoid the intrinsic defect of LiNio.8Coo.15Alo.05O2, the performance of LiNio.8Coo.15Alo.05O2 was improved by surface modification。The spherical Ni0.8Co0.15Al0.05(OH)x precursor was prepared by the method of controlled crystallization. The cathode material LiNio.8Coo.15Al0.05O2 is prepared from the spherical Ni0.8Co0.i5Al0.05(OH)x precursor by heat treatment. The influences of pretreatment temperature, pretreatment time, synthesis temperature, synthesis time on the performance of cathode material were studied. The optimized conditions were got:the spherical precursor is pretreated at 750℃in 4h, then mixed with lithium (theory 105%) and kept 15h at 750℃in oxygen, cooled along with stove.The samples synthesized under optimized conditions show good electrochemical performance. It have discharge capacity of 203.2mAh/g, 192.4mAh/g,185.9mAh/g,166.2mAh/g,155.7mAh/g and 146.8mAh/g at 0.1C,0.2C,0.5C,1C and 2C rate. After 30 circles, The capacity retention are 93.7% and 93.3% at 0.2C and 2.5C rate.The effect of different surface modification motheds and different coated compnents on the performance of cathode materials were studied. LiCoO2-coated LiNi0.8Coo.15Al0.05O2 materials prepared by precipation mothed show the best electrochemical performance.1.2wt%Co-coated materials has discharge specific capacity of 191.7mAh/g at 0.2C rate and 55℃. After 38 circles, Capacity retention is 93.7%. Compared to uncoated materials, coated materials have better electrochemical performance at high temperature. SiO2-coated LiNi0.8Co0.15Al0.05O2 materials prepared by sol gel mothed improve electrochemical performance at 55℃. The material coated 1.0%wt SiO2 has high capacity. Its first discharge capacity is 199.1 mAh/g at 0.1C rate and 55℃. It also has discharge capacity of 191.9 mAh/g at 0.2C rate and 55℃. After 30 circles, the capacity retention is 94.6%.更多还原