%0 Journal Article
%T <br>
%A 张泽
%A 曾跃武
%A 邬春阳
%A 金传洪
%A 黄威
%J 物理化学学报
%D 2016
%R 10.3866/PKU.WHXB2016032802
%X 采用球差校正扫描透射电子显微镜(STEM)、X射线能谱(EDS)等分析手段表征了高温固相法合成的Na0.66Mn0.675Ni0.1625Co0.1625O2钠离子过渡金属氧化物正极材料。X射线衍射(XRD)结果表明该材料为结晶性良好的P2型钠离子层状氧化物(P63/mmc)。原子尺度的结构与成分分析显示材料表面存在宽度约为1-2 nm的表面重构层，重构区域内存在大量晶格畸变与反位缺陷，并伴有一定程度的成分偏析——表面富钴(Co)、缺镍(Ni)。进一步研究表明这些表面重构区域在时效过程中会发生明显的“退化”，即初始表面重构层宽度会进一步扩展至5-10 nm，部分区域钠离子耗尽，由层状结构转变为尖晶石(Spinel,Fd3m)与岩盐相(rocksalt,Fm3m)共存的结构。<br>We performed an aberration-corrected scanning transmission electron microscopy(STEM)andenergy-dispersive X-ray spectroscopy(EDS)study of Na0.66Mn0.675Ni0.1625Co0.1625O2,which was prepared via a solidstatereaction for sodium-ion battery applications.Powder X-ray diffraction(XRD)showed that the material hada well-crystallized P2-type layered structure(P63/mmc).Results from further STEM and EDS analyses showedthe presence of reconstructed surface layers of thickness about 1-2 nm,which contained a large amount ofantisite defects and obvious lattice distortions.Detailed chemical analysis showed an inhomogeneous elementaldistribution inside these reconstructed surface layers;they were cobalt rich and nickel deficient.These surfacelayers further evolved into thicker regions of width 5-10 nm,accompanied by a spinel(Fd3m)phase to rocksaltphase(Fm3m)transition
%U http://www.whxb.pku.edu.cn/CN/Y2016/V32/I6/1489