Electrochemical Behavior of Nonstoichiometric LiMn2-xNixO4 as a 5-V Cathode Material

Abstract

The average voltages of LiNi_xMn_2-xO₄ in the 5-V region discontinuously increase from 4.58-4.59 V to 4.65-4.71 V with an increase in the Ni content. A slope analysis suggests that the prepared samples are nonstoichiometric and contains approximately a 1% cation vacancy and that the valences of Ni are 3+ for 0< x 0.1 The Ni valence results have been supported by the high-resolution X-ray fluorescence spectra data. These results suggest that the redox couples in LiNi_xMn_2-xO₄ change from Ni³⁺/Ni⁴⁺ to Ni²⁺/Ni⁴⁺ at x =0.057-0.089.