Surface modification of Li_1.6(Fe_0.2Ni_0.2 Mn_0.6)O_2.6 by V₂O₅-coating

We presented a method to improve the first discharge capacity and the cycling performance of Li_1.6(Fe_0.2Ni_0.2 Mn_0.6)O_2.6 which was synthesized by a coprecipitation-hydrothermal-calcinations method and coated by a V₂O₅ layer on the surface of Li_1.6(Fe_0.2Ni_0.2 Mn_0.6)O_2.6. The crystal structure and the charge/discharge performance of Li_1.6(Fe_0.2Ni_0.2 Mn_0.6)O_2.6 were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), inductively coupled plasma (ICP) and electrochemical performance measurement. Results show that V₂O₅ exists only on the surface, and has no effect on the crystal structure; the Li_1.6(Fe_0.2Ni_0.2 Mn_0.6)O_2.6 coated with V₂O₅ exhibits better first discharge capacity than the bared Li_1.6(Fe_0.2Ni_0.2 Mn_0.6)O_2.6. The electrochemical tests demonstrate that Li_1.6(Fe_0.2Ni_0.2 Mn_0.6)O_2.6 coated with 3 wt% V₂O₅ shows the best electrochemical performance with the discharge capacity 200.3 mAh/g after 50 cycles, while the bared sample has 194.0 mAh/g only. CV results indicate that the V₂O₅ coating can suppress the phase transitions and prevent the surface of cathode materials from the direct contact with the electrolyte.