湿化学法合成LiNi_(1/3)Mn_(1/3)Co_(1/3)O_2及其表征(英文)

Characterization of LiNi_(1/3)Mn_(1/3)Co_(1/3)O_2 Synthesized by Wet-Chemical Method

利用琥珀酸为鳌合剂的湿化学法成功合成了一系列锂离子电池正极材料LiNi1/3Mn1/3Co1/3O2,在合成过程中改变琥珀酸与金属离子摩尔比(R)并研究了这一参数对合成LiNi1/3Mn1/3Co1/3O2材料物理及电化学性质的影响.采用热重、X射线衍射、Rietveld精修、扫描电镜以及超导量子干涉仪对反应机理、材料的结构、形貌以及磁学性质进行了详细表征.得到最佳合成条件为R=1,此时LiNi1/3Mn1/3Co1/3O2的阳离子混排度最低.此外,通过Rietveld精修得到该材料阳离子混排度的结果与通过磁学方法得到的结果定量相符,如对于在R=1条件下合成的样品,Rietveld精修结果显示其阳离子混排度为1.85%,而超导量子干涉仪的测试结果为1.80%.当充放电区间为3.0-4.3V,电流密度为0.2C(1C=160mA·g-1)时,该样品的首次放电容量为161mAh·g-1,库仑效率为93.1%,经过50次循环后,容量保持率可达91.3%.

A series of cathode materials LiNi1/3Mn1/3Co1/3O2 for lithium-ion batteries were successfully synthesized using succinic acid as a chelating agent by a wet-chemical method.We varied the succinic acid to metal-ion molar ratios（R） and investigated the effect of this parameter on the physical and electrochemical properties of the prepared LiNi1/3Mn1/3Co1/3O2.The reaction mechanism,structural,morphological,and magnetic properties of the powders were characterized in detail by thermogravimetry（TG）,X-ray diffraction（XRD）,Rietveld refinement,scanning electron microscopy（SEM）,and superconducting quantum interface device（SQUID）.We determine that the optimum conditions for the synthesis of LiNi1/3Mn1/3Co1/3O2 assisted with succinic acid is R=1,at the lowest amount of cation mixing.In addition,measurement of the magnetic properties revealed a concentration of Ni on the 3b Wyckoff site of the lithium-ions in good agreement with the results from the Rietveld refinement on the XRD spectra.For LiNi1/3Mn1/ 3Co1/3O2（R=1）,the Rietveld refinement showed that cation mixing in this sample was 1.85%,which is in quantitative agreement with that from the SQUID result（1.80%）.It delivered an initial discharge capacity of 161 mAh·g-1 at a current rate of 0.2C（1C=160 mA·g-1） and at a cut-off voltage of 3.0-4.3 V with a coulombic efficiency of 93.1% and its capacity retention was 91.3% after 50 cycles.