The electrochemical performance of yttrium oxide coated LiNi _1/3Mn _1/3Co _1/3O ₂ as cathode material for lithium-ion batteries

The surface of LiNi _1/3Mn _1/3Co _1/3O ₂ was coated with 1.0 wt.% Y ₂O ₃ to improve the cycling performance for lithium-ion batteries. X-ray diffraction (XRD) of the coated material indicates Y ₂O ₃-coating does not destroy the crystal structure of LiNi _1/3Mn _1/3Co _1/3O ₂, only forming a compact coating layer on the surface of it. Differential scanning calorimetry-thermal gravimetric analyses (DSC-TGA) results show the coating layer could suppress the heating release. The Y ₂O ₃-coated LiNi _1/3Mn _1/3Co _1/3O ₂ possesses higher discharge capacity and better cyclability than that of the bared material. The discharge capacity of coated sample is 100.7 mAh g ^-1 at 2.0 C while that of bared one is only 80.0 mAh g ^-1. The rate of capacity retention after 12 cycles for the coated sample is 100% at 333 K, which is much better than that of the bared one (94.9 %). The chemical diffusion coefficient of Li ⁺ ion (D _Li) in the electrodes were measured by potentiostatic intermittent titration technique (PITT). The result shows that Li ⁺ ion can move faster after coating.