锂离子电池正极材料LiNi_(1/2)Co_(1/6)Mn_(1/3)O_2的制备与性能

Synthesis and Characterization of Cathode Material LiNi_(1/2)Co_(1/6)Mn_(1/3)O_2 for Lithium-ion Secondary Batteries

采用Co^2＋浓度递增的金属离子混合溶液分次共沉淀方法制备Ni1/2Co1/6Mn1/3（OH）2，以其为前驱体，通过高温固相反应得到具有Co含量梯度的层状LiNil，2Co1/6Mn1/33O2，探讨了焙烧温度及Co含量梯度对材料的结构和电化学性能的影响．通过X射线衍射、扫描电镜、热重分析及恒电流充放电测试对合成的样品进行了表征．结果表明，700℃合成产物即具有类LiNiO2的六方层状结构，800和850℃合成产物阳离子排列有序度高，层状结构显著．材料结晶度好，粒度均匀，粒径在亚微米级．合成温度800℃的梯度材料具有最佳的电化学性能，2．5～4．2V0．1C倍率充放电50次后，梯度材料的容量仍保持在171．2mA．h/g．相同的焙烧温度，梯度材料比均匀材料的电化学性能更加优异．

Layered gradient composite, LiNi1/2Co1/6Mn1/3O2 was synthesized by mixing co-precipitated gradient hydroxide Ni1/2Co1/6Mn1/3（OH）2 with 5% excess LiOH.H20 followed by heat treatment. The precursor Ni1/2Co1/6Mn1/3（OH）2 was prepared via multiple co-precipitation of solutions with different compositions of Ni^2＋, Co^2＋, Mn^2＋. The cathode material was characterized using X-ray diffraction （XRD）, scanning electron microscope （SEM）, galvanostatic charge-discharge test and electrochemical impedance spectroscopy （EIS）. The XRD pattern and the SEM photos of the material indicated that the layered crystal structure of the material with α-NaFeO2 type （space group R3m） was perfect and its morphology was well distributed. The galvanostatic charge-discharge （0.1 C, 2.5-4.2 V, vs. Li^＋/Li） tests showed that not only the first discharge specific capacity of the gradient material was higher than that the homogeneous material, but its cyclic stability was improved greatly. The gradient material sintered at 800 ℃ delivered high discharge specific capacity of 171.2 mA.h/g after multiple cycling.