Preparation of spinel LiNi0.5Mn1.5O4 and Cr-doped LiNi0.5Mn1.5O4 cathode materials by tartaric acid assisted sol–gel method

In this article, LiNi 0.5 Mn 1.5 O 4 and LiNi 0.4 Cr 0.15 Mn 1.45 O 4 are prepared by the tartaric acid-assisted sol–gel method. It can be found that Cr doping not only can suppress the formation of impurity phase in the final product but also can increase the cation ordering in the spinel structure. Morphology observation reveals that the introduction of tartaric acid in the preparation leads to a controlled cubic morphology and a narrow particle size distribution . It is clear that both LiNi 0.5 Mn 1.5 O 4 and LiNi 0.4 Cr 0.15 Mn 1.45 O 4 consist of octahedrons with the particle size ranging from 0.5 to 1.5   μm. Charge/discharge tests show that LiNi 0.4 Cr 0.15 Mn 1.45 O 4 can deliver a higher initial discharge capacity (143.9   mAh   g −1 ) than that of undoped LiNi 0.5 Mn 1.5 O 4 (136.6   mAh   g −1 ). After 40 cycles, the reversible discharge capacity of LiNi 0.4 Cr 0.15 Mn 1.45 O 4 can be still maintained at 139.7   mAh   g −1 . For comparison, LiNi 0.5 Mn 1.5 O 4 only shows a reversible discharge capacity of 127.7   mAh   g −1 . It suggests that Cr substitution for Ni and Mn in the spinel structure can effectively improve the electrochemical performance of LiNi 0.5 Mn 1.5 O 4.