Electrochemical behaviour of Al-doped Li(Ni 0.5-x Al 2x Mn 0.5-x )O 2 with large Al content by the sol-gel method

Layered Li(Ni 0.5-x Al 2x Mn 0.5-x )O 2 (x=0 and 0.1) (Mn/Ni = 1) were synthesized by sol-gel method using citric acid as a chelating agent. The Structure, electrochemical properties of prepared cathode materials were measured by means of X-ray diffraction, cyclic voltammetry, galvanostatic charge-discharge test and AC impedance spectra. The measured results indicate that, (1) the Al-doped sample has the better layered-structure; (2) compared to Li(Ni 0.5 Mn 0.5 )O 2 , the discharge capacity of Li(Ni 0.4 Al 0.2 Mn 0.4 )O 2 is evidently increased and reaches 160 mAhg −1 between 2.8 and 4.2V at the rate of 20 mAg −1 ; (3) Al ion in Li(Ni 0.5-x Al 2x Mn 0.5-x )O 2 not only replaces Ni 2+ as an active materal, but also can substitute Mn 4+ used for supporting structure. Moreover, the electrochemical impedance spectra of the samples are also discussed.