The effects of sulfur doping on the performance of O3-Li0.7[Li1/12Ni1/12Mn5/6]O2 powder

Li_0.7Li_1/12Ni_1/12Mn_5/6]O₂ and Li_0.7Li_1/12Ni_1/12Mn_5/6]O_2-yS_y (y=0.1, 0.2, 0.3) powders were synthesized by using a sol-gel method. As-prepared samples showed typical rhombohedral O3 layered structure. The shape of the initial discharge curve for the samples was almost equal to that of the layered structure. However, the electrode materials were transferred from layered to spinel structures with cycling. At the first cycle, Li_0.7Li_1/12Ni_1/122Mn₂5/6]O₂ and Li_0.7Li_1/12Ni_1/12 Mn_5/6]O_1.9S_0.1, Li_0.7Li_1/12Ni_1/12Mn_5/6]O_1.8S_0.2, and Li_0.7Li_1/12Ni_1/12Mn_5/6]O_1.7S_0.3 delivered the discharge capacities of 238, 230,224, and 226 mAh/g, respectively, with their capacity fading rates of 0.34, 0.21, 0.12, 0.25%/cycle, respectively. The partial substitutions of Ni and S for Mn and O in Li_0.7Li_1/12Ni_1/12Mn_1/12]O₂ significantly enhanced the electrochemical properties of the lithium manganese oxide materials.