Preparation And Modification Of Lithium Ion Battery LiNi_0.8Co_0.05O₂ Cathode

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%.