初始Li/(Mn+Ni)摩尔比对LiNi0.5Mn0.5O2电化学性能的影响

来源期刊:中国有色金属学报2006年第8期

论文作者:王志兴 曹四海 李新海 郭华军 彭文杰

文章页码:1434 - 1438

关键词:LiNi0.5Mn0.5O2;锂离子电池; 正极材料; 电化学性能; 一步固相法

Key words:LiNi0.5Mn0.5O2; Li-ion battery; cathode; electrochemical performance; one-step solid state reaction

摘    要:以Li2CO3, MnCO3和Ni(OH)2为原料,采用一步固相反应制备锂离子电池层状结构正极材料LiNi0.5Mn0.5O2,采用X射线衍射和扫描电镜对其结构和形貌进行表征, 并研究配料时不同初始Li/(Mn+Ni)摩尔比(1.0, 1.05, 1.1, 1.2, 1.5)对LiNi0.5Mn0.5O2电化学性能的影响。 X射线衍射结果表明, 在600 ℃预烧12 h而后800 ℃烧结24 h的条件下各样品结晶完整, 初始Li/(Mn+Ni)摩尔比为1.5时样品有未知相杂质生成。 扫描电镜分析表明, 随着初始Li/(Mn+Ni)摩尔比的增大,颗粒团聚加剧。 电化学测试结果表明, 随着初始Li/(Mn+Ni)摩尔比(≥1.05)的提高,初始容量有下降趋势。 初始Li/(Mn+Ni)摩尔比为1.05和1.1时样品首次放电容量分别为167.0 mA·h/g和147.2 mA·h/g,循环20次后容量保持率分别为88.2%和97.8%。

Abstract: Cathode material LiNi0.5Mn0.5O2 with layered structure was synthesized using Li2CO3, MnCO3 and Ni(OH)2 as starting materials by one-step solid state reaction. The structure and morphology of the synthesized samples were characterized by X-ray diffractrometry and scanning electron microscopy, respectively. And the effect of initial Li/(Mn+Ni) mole ratio on the electrochemical performance of LiNi0.5Mn0.5O2 was studied. X-ray diffraction results show that the samples synthesized at 600 ℃ for 12 h, followed by calcination at 800 ℃ for 24 h were well crystallized. Some uncertain impurity existed in the sample with initial Li/(Mn+Ni) mole ratio of 1.5. Scanning electron microscope photographs show that the conglomeration of particles becomes more serious with increasing initial Li/(Mn+Ni) mole ratio. When initial Li/(Mn+Ni) mole ratio is equal to or more than 1.05, initial discharge capacity decreases with increasing initial Li/(Mn+Ni) mole ratio. The first discharge capacities of samples with initial Li/(Mn+Ni) mole ratio of 1.05 and 1.1 are 167.2 and 147.2 mA·h/g respectively at a specific current of 20 mA/g between 2.5 V and 4.5 V, and retain 88.2% and 97.8% of the initial capacity respectively after 20 cycles.

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