Synthesis and characterization of LiCoO ₂-coated LiNi _0.8Co _0.15Al _0.05O ₂ cathode materials

An electrochemically active LiCoO ₂ layer was coated onto the surface of LiNi _0.8Co _0.15Al _0.05O ₂ by a molten salt method. The 3.0 wt.% LiCoO ₂-coated LiNi _0.8Co _0.15Al _0.05O ₂ exhibited excellent electrochemical performance, with an initial discharge capacity of 196.2 mAh·g ^{- 1} and capacity retention of 98.7% after 50 cycles when cycled at 0.2 C rate between 2.8 and 4.3 V. Moreover, the cycle performance and rate capability of the coated sample were better than that of the bare one. Electrochemical impedance spectroscopy measurements showed that the decrease of NiO-type surface layer on the coated sample is the major reason for the improvement of electrochemical performance of LiCoO ₂-coated LiNi _0.8Co _0.15Al _0.05O ₂ cathode.