球形LiNi0.5-xCo2xMn0.5-xO2的合成及其电化学性能

无机材料学报, 2007, 22(5): 873-878. doi: 10.3724/SP.J.1077.2007.00873

球形LiNi_0.5-xCo_2xMn_0.5-xO₂的合成及其电化学性能

School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China

关键词：锂离子电池 , cathode material , spherical , LiNi_0.5-xCo_2xMn_0.5-xO₂

Synthesis and Electrochemical Performance of Spherical LiNi_0.5-xCo_2xMn_0.5-x O₂

ZHU Yong-Jun , LI Xin-Hai , WANG Zhi-Xing , YANG Zhi , HU Qi-Yang

Keywords： Li-ion battery , 正极材料 , 球形 , LiNi_0.5-xCo_2xMn_0.5-xO₂

以化学共沉淀法制备的球形Ni_0.5-xCo_2xMn_0.5-xCO₃(x=0.075, 0.1, 1/6)为前驱体合成了球形锂离子电池正极材料LiNi_0.5-xCo_2xMn_0.5-xO₂(x=0.075, 0.1, 1/6), 研究了钴含量对LiNi_0.5-xCo_2xMn_0.5-xO₂的物理性能和电化学性能的影响. SEM研究表明, 球形LiNi_0.5-xCo_2xMn_0.5-xO₂由许多一次颗粒构成, 随着钴含量的增加, 产物中一次颗粒增大. XRD分析表明, LiNi_0.5-xCo_2xMn_0.5-xO₂ 均为具有层状结构的纯相物质. 电化学性能测试结果显示, LiNi_0.5-xCo_2xMn_0.5-xO₂随着钴含量的增加, 材料的充放电容量提高, 且循环性能变好: 0.2C倍率下、2.7～4.3V的电压范围内, LiNi_0.425Co_0.15Mn_0.425O₂的放电比容量为145mAh·g^-1、LiNi_0.4Co_0.2Mn_0.4O₂为150mAh·g^-1、LiNi_1/3Co_1/3Mn_{1/ 3}O₂为158mAh·g^-1, 循环50周期后LiNi_0.425Co_0.15Mn_0.425O₂和LiNi_0.4Co_0.2Mn_0.4O₂的容量衰减率在3％以内, LiNi_1/3Co_1/3Mn_1/3O₂容量无衰减. 交流阻抗测试结果表明, 随着钴含量的增加, 材料阻抗值减小.

Spherical LiNi_0.5-xCo_2xMn_0.5-xO₂(x=0.075, 0.1, 1/6) powders were synthesized from the co-precipitated carbonate precursor, Ni_0.5-xCo_2xMn_0.5-xCO₃(x=0.075, 0.1, 1/6). The effects of the Co content on the physics and electrochemical performance of LiNi_0.5-xCo_2xMn_0.5-xO₂ were investigated. The SEM images of LiNi_0.5-xCo_2xMn_0.5-xO₂ show that the spherical material consists of many primary particles, which sizes increase with the content of Co increasement. The results of X-ray powder diffraction show that all LiNi_0.5-xCo_2xMn_0.5-xO₂are pure phase materials with layered structures. The electrochemical tests indicate that the discharge capacities of LiNi_0.5-xCo_2xMn_0.5-xO₂ increase and the cycle performances become better with the content of Co increasing. Under the charge/discharge conditions of 0.2C rate and voltage range of 2.7--4.3V, the discharge properties of spherical LiNi_0.425Co_0.15Mn_0.425O₂, LiNi_0.4Co_0.2Mn_0.4O₂ and LiNi_1/3Co_1/3Mn_1/3O₂are 145,150 and 158 mAh·g^-1, respectively. The discharge capacity fadings for LiNi_0.425Co_0.15Mn_0.425O₂ and LiNi_0.4Co_0.2Mn_0.4O₂ are less than 3％ , however, there is no fade for that of LiNi_1/3Co_1/3 Mn_1/3O₂after 50 cycles. The results of AC impedance show that the impedance decreases with the content of Co increasing.

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