Electrochemical performance of layered Li[Ni xCo 1−2 xMn x]O 2 cathode materials synthesized by a sol–gel method

Abstract

Synthesis and characterization of LiNi x Co 1−2 x Mn x O 2 (1/3 ≤ x ≤ 1/2) electrode powders prepared by a sol–gel method were investigated. The synthesized LiNi x Co 1−2 x Mn x O 2 materials with single phase and R 3 ¯ m layered structure were confirmed from X-ray diffraction analysis. The particle size distribution of the materials synthesized by the sol–gel process is quite uniform. Increasing the x value in the synthesized LiNi x Co 1−2 x Mn x O 2 powder leads to decrease its particle size and increase its cation mixing. The average particle size for the LiNi 0.375Co 0.25Mn 0.375O 2 powder was found to be an order of 0.3–0.4 μm. The best specific capacity of 192 mAh g −1 was obtained for the LiNi 0.375Co 0.25Mn 0.375O 2 electrode with good capacity retention among the synthesized materials cycled at 0.1C in the potential between 3.0 and 4.5 V at room temperature. Although structural parameters of the LiNi 0.375Co 0.25Mn 0.375O 2 powder are similar to those of the LiNi 1/3Co 1/3Mn 1/3O 2 powder, its specific capacity is higher due to the increase of the stoichiometry of active site Ni. The increase of Ni and Mn content could reduce cost of the materials. It was found that the cell performance of the LiNi x Co 1−2 x Mn x O 2 electrode drops dramatically and its cation mixing increases while the x value is higher than 0.4.