Enhanced electrochemical performance of F-doped Li_1.2Mn_4/6Ni_1/6Co_1/6O_2.35 cathode materials for Li-ion batteries

F-doped cathode material Li_1.2Mn_4/6Ni_1/6Co_1/6O_(2.35-x)F_x (x=0,0.05,0.10,0.15) were synthesized successfully by two-step co-precipitation method. X-ray diffraction pattern shows that fluorine doping does not bring impurities, but the lattice parameters increase slightly with fluorine content increasing in Li_1.2Mn_4/6Ni_1/6Co_1/6O_(2.35-x)F_x. At the current density of 0.5C (125mAhg^-1), Li_1.2Mn_4/6Ni_1/6Co_1/6O_2.30F_0.05 has the highest capacity retention (94.56%) and discharge capacity(177.4mA•h/g) after 50th cycles, while capacity retention and discharge capacity after 50th cycles of Li_1.2Mn_4/6Ni_1/6Co_1/6O_2.35 material are only 86.19% and 164.7 mA•h/g. And Li_1.2Mn_4/6Ni_1/6Co_1/6O_2.30F_0.05 material exhibits a noticeable higher discharge capacity than other Li_1.2Mn_4/6Ni_1/6Co_1/6O_(2.35-x)F_x (x=0, 0.10,0.15) materials at high current density. The initial discharge specific capacity of Li_1.2Mn_4/6Ni_1/6Co_1/6O_2.30F_0.05 material is increased to 121.1 mA•h/g and 82.3 mA•h/g compared to 91.1 mA•h/g and 66.8 mA•h/g of Li_1.2Mn_4/6Ni_1/6Co_1/6O_2.35 material at 2C and 5C. It can be concluded that electrochemical performances of Li_1.2Mn_4/6Ni_1/6Co_1/6O_2.35 material are improved due to fluorine doping.