Characterization of Thin and Uniform Carbon Coated Overlithiated Layer Oxide Cathode Material for Lithium Ion Batteries

Thin and uniform carbon coated overlithiated layer oxide (OLO) using 2,3-dihydroxynaphthalene (DN) is prepared. The pristine and DN coated samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). An amorphous nanolayer coating of carbon is obtained on the surface of layered pristine material. The coating layer was confirmed by TEM analysis. The thickness of coating layer was approximately 5 nm, when the content of DN coating was 0.2 wt.%. For optimization of coating condition, the coating weight and the temperature of heat treatment was changed. The 0.1wt% DN coated OLO which was heated at 500^oC exhibits the improved electrochemical performance. The initial discharge capacity of 202 mAh·g⁻¹ is obtained at 1C. This capacity is larger of 2% than that of bare OLO. The capacity retention (93.9% at 50^th cycle) is also maintained compared to bare OLO (92.3% at 50^th cycle). The average voltage drop of coated OLO showed 20mV lower than that of bare sample after 50^th cycle. The thin and uniform carbon layer leads to improvement of kinetic and protection of direct contact between cathode and electrolyte.

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