Electron Microscopy Study of Surface Reconstruction and Its Evolution in P2-Type Na0.66Mn0.675Ni0.1625Co0.1625O2 for Sodium-Ion Batteries
Wei HUANG,Chun-Yang WU,Yue-Wu ZENG,Chuan-Hong JIN,Ze ZHANG.Electron Microscopy Study of Surface Reconstruction and Its Evolution in P2-Type Na0.66Mn0.675Ni0.1625Co0.1625O2 for Sodium-Ion Batteries[J].Acta Physico-Chimica Sinica,2016,32(6):1489-1494.
State Key Laboratory of Silicon Materials, Key Laboratory of Advanced Materials and Applications for Batteries of Zhejiang Province, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China
Abstract:
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.
