Preparation and characterization of fluorine and magnesium co-doping LiNi0.8Fe0.1Al0.1O2 cathode materials for lithium-ion batteries

With the vigorous development of new energy vehicles, cobalt in the traditional lithium-ion(Li-ion) battery industry chain is obviously in short supply. To manage this challenge, a new cobalt-free cathode material Li[Ni0.8Fe0.1Al0.1]1-xMgxO2-yFy (x = 0.01, y = 0.01, 0.02, 0.03) with different f-doping contents (labeled Mg-1, Mg-F-1, Mg-F-2, Mg-F-3) was prepared by sol-gel method. XRD results show that the co-doping of Mg2+ and F- reduces the mixing degree of cations and increases the lattice parameters. A small amount of Mg2+ and F- co-doping does not affect the layered structure of NFA materials. The results of SEM, EDS, and elemental spectrum showed that Mg and F elements were evenly dispersed on the surface of the material and successfully doped into the crystal structure of the material. The co-doping of Mg2+ and F- did not damage the surface of NFA primary particles. XPS results further confirmed that Mg2+ and F- were introduced successfully into NFA materials. Compared with the original NFA material, the co-doping of Mg2+ and F- significantly improved the electrochemical performance of the pristine material. Electrochemical results show that co-doping has the best first discharge-specific capacity, first-coulomb efficiency, and cycle life. The first discharge-specific capacity and coulomb efficiency at 0.1 C and 10 C were 171.8 mAh g-1, 88.1%, and 143.4 mAh g-1, 71.72%, respectively. After 150 cycles, the capacity retention rate was 88.1% and 71.90%. This study emphasizes the broad prospects of this new material in the future cobalt-free market.