O2结构Li_y[Mn_(1-x)M_x]O_2(M=Cr,Mg)的合成及结构研究  

Preparation and Crystal Structure of Li_y[Mn_(1-x)M_x]O_2(M=Cr,Mg) with the Layered O2 Structure

作　　者：路艳罗[1] 卫敏[1] 杨文胜[1] EVANS D.G. 段雪[1] 

机构地区：[1]北京化工大学可控化学反应科学与技术基础教育部重点实验室,北京100029

出　　处：《化学学报》2003年第6期858-862,共5页Acta Chimica Sinica

基　　金：国家高技术研究发展计划 (863计划 ) (No.2 0 0 1AA32 30 2 0 );北京化工大学青年教师科研基金(No.QN0 1 36);北京市科技新星计划 (No.H0 1 361 0 350 1 1 2 )资助项目

摘　　要：由高温焙烧法制备层状前驱体Na2 /3 [Mn1-xMx]O2 (M =Cr,Mg) ,再经离子交换反应得到层状O2结构产物Liy [Mn1-xMx]O2 .XRD表明Liy[Mn1-xMx]O2 属六方晶系 ,P3ml空间群 .Cr的添加量对前驱体的晶体结构有很大影响 :随着x值的增大 ,前驱体逐渐由层状P2结构Na2 /3 [Mn1-xCrx]O2 向正交结构Na4Mn9O18转变 .由SEM可以看到样品Liy[Mn1-xCrx] O2 (x≤ 0 .0 5 )具有六方层状结构 .XPS分析结果表明样品Liy[Mn0 .95Cr0 .0 5]O2 表面上的Mn和Cr分别以Mn4+和Cr4+存在 ,并且表面中Cr相对含量高于体相 ,而样品Liy[Mn0 .90 Mg0 .10 ]O2 的表面Mn和Mg分别以Mn4+和Mg2 +存在 。Precursors of the P2 type Na-2/3[Mn1-xMx]O-2 ( M = Cr, Mg) were prepared by solid state reaction methods and Li-gamma[Mn1-xMx]O-2 materials were obtained by ion-exchange. XRD patterns indicate that Li-gamma[Mn1-xMx]O-2 has the layered O2 structure with the hexagonal space group P3ml. It is shown by XRD that the structure of the Cr-doped precursors is influenced by the dopant content. When 0 less than or equal to x less than or equal to 0.05, Na-2/3[Mn1-xCrx]O-2 materials with the P2 structure were obtained. When x > 0.05, the structure was gradually changed from P2 structure to orthorhombic Na4Mn9O18. X-ray photoelectron spectra indicate that surface and bulk compositions of Li-gamma[Mn0.95Cr0.05]O-2 are different. The oxidation states of manganese and chromium in the near-surface region are largely tetravalent and the Cr/Mn ratio in the near-surface region is higher than that in the bulk. The presence of Mn4+ and Cr-rich surface layers leads to an improvement in the stability of the material. In the case of the Mg-doped compounds, however, layered O2-type structure Li-gamma[Mn1-xMgx]O-2 materials can be obtained in the range of 0 less than or equal to x less than or equal to 0.15. The layered structure becomes more distinct as the content of Mg increases. The Mg/Mn ratio in the near-surface region is consistent with that in the bulk, indicating the formation of stoichiometric Mg-Mn mixed oxides.

关 键 词：层状材料 晶体结构 合成 表面分析 锂锰复合氧化物 锂离子二次电池 正极材料 氧分子 

分 类 号：TM911[电气工程—电力电子与电力传动]