Beijing Univ Technol, Coll Environm & Energy Engn, Beijing 100022, Peoples R China
; Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China
Structural modifications in LiNiO2 induced by doping of Al, Co and Mn were investigated by XRD and EXAFS. Diffraction experiments show that doping does not modify the phase as LiNiO2, and all structures belong to the R (3) over barm group, however, doping of Al, Co and Mn, decreases the size of the unit cell, and limits the cation mixing in lithium layers. From EXAFS data filling one may see that doping of Al, Co and Mn decreases the Debye-Waller factor of the first shell of Ni-O and weakens the John-Teller distortion of the Ni(III)O-6 octahedron. Doping by Al and Co in LiNiO2 also decreases the Ni-O bond length while the effect on bond length not obrious with Mn doping. All dopings decrease also the second shell Ni-Ni bond length. Moreover, doping of Co and Mn decreases the Debye-Waller factor of the second shell increasing the ordering of the Ni-Ni shell, while Al doping increases the Debye-Waller factor and slightly enhances the disorder degree of the Ni-Ni shell.