Abstract
The layered cathode materials 0.65Li[Li 1/3Mn 2/3]O 2·0.35LiMO 2 (M = Co, Ni 1/2Mn 1/2 and Ni 1/3Co 1/3Mn 1/3) were synthesized by a low-heating solid state reaction. The XRD results showed that the superlattice peaks became weaker as the Co content increased and the involvement of Co helped to reduce the cation mixing. When cycled between 2.5 and 4.4 V at 0.5 C, the Ni 1/2Mn 1/2 and Ni 1/3Co 1/3Mn 1/3 containing electrodes showed excellent cycle performances and their capacities increased with the introduction of cobalt. However, when the electrodes were cycled between 2.5 and 4.6 V at 0.5 C, their discharge capacities increased gradually with cycling to a maximum. As the amount of Co increases, the number of cycles that were required to reach the maximum capacity decreases. According to the d Q/d V curves it was found that the presence of cobalt ions in the structure could accelerate the irreversible reaction above 4.5 V. Furthermore, the presence of cobalt seems to lead to the deterioration of the high potential electrochemical performance of the materials.
Published Version
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