Syntheses and Performance of layered LiNi_xCo_(1-2x)Mn_xO_2 as Cathode Materials for Lithium-Ion Batteries

摘要

The layered cathode materials LiNi_xCo_(1-2x)Mn_xO_2(x=1/11, 2/11, 3/11, 4/11, 5/11) powders for lithium-ion batteries were synthesized by metal acetate decomposition technique. The evolution of the structural properties and electrochemical performances of LiNi_xCo_(1-2x)Mn_xO_2 with Co content decreased were investigated by X-ray diffraction (XRD) and rietveld refinement, scanning electronic microscopy (SEM) and galvanostatic charge and discharge cycle. The results showed that the appropriate substitution of Co by Ni, Mn could greatly improve the performances of the as-prepared materials in capacity, initial columbic efficiency, rate ability and cycle capability. Among the series of materials, the optimal performance belonged to Li Ni_(3/11)Co_(5/11)Mn_(3/11)O_2, which delivered an initial discharge capacity of 157.6 mAh·g~(-1) and preserved 150.4 mAh·g~(-1) after 30 cycles in the voltage range of 2.5 ～ 4.3 V at 0.2 C. Comparative cycle data at 0.5 C and 1.0 C were presented implying that the LiNi_(3/11)Co_(5/11)Mn_(3/11)O_2 also had a significantly improvement in rate capability.