The effects of Na doping on performance of layered Li1.1-xNax[Ni0.2Co0.3Mn0.4]O2 materials for lithium secondary batteries

Layered Li1.1-xNax[Ni0.2Co0.3Mn0.4]O-2 (x= 0, 0.05, 0.1 and 0.2) materials with high homogeneity and high crystallinity were prepared by a sol-gel method. Structural and electrochemical properties of the Li1.1-xNax[Ni0.2Co0.3Mn0.4]O-2 materials were characterized by means of powder X-ray diffraction, and galvanostatic charge/discharge cycling. Na-doped samples had a phase-pure layered structure with a space group of R3m (No. 166). Although, the discharge capacity decreased linearly with increases of Na-substitution, only a few of the Na-doped (x = 0.05, 0.1) electrodes exhibited superior rate capability and good capacity retention. (c) 2005 Published by Elsevier B.V.