Vanadium-doped lithium-rich layered-structured cathode material Li1.2Ni0.2Mn0.6O2 with a high specific capacity and improved rate performance

Abstract

Fine powders of Li_1.2Ni_0.2Mn_0.6−xV_xO₂ (x = 0, 0.002, 0.005, 0.01, 0.02) are prepared by a thermopolymerization method. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and electrochemical measurements are carried out to characterize these samples. The V-doped samples show great improvement in rate performance and cycling stability, as well as mitigation of voltage decline during cycling. For the optimal composition Li_1.2Ni_0.2Mn_0.59V_0.01O₂, it exhibits a discharge capacity of 245 and 118 mA h g⁻¹ at 0.1C and 10C rates, respectively. It retains a capacity of 234 mA h g⁻¹ at 0.1C after 188 cycles with a capacity retention of 95.5%. This study suggests that the partial substitution of Mn⁴⁺ with V⁵⁺ can improve both the rate capability and cycle stability of this high-capacity cathode material.