Synthesis of Spherical Fluorine Modified Gradient Li-Ion Battery Cathode Material LiNi_0.80Co_0.15Al_0.05O₂by Simple Solid Phase Method

The high nickel layer cathode LiNi 0.80 Co 0.15 Al 0.05 O 2 (NCA) has excellent discharge capacity and better cycling performance. However, the NCA cathode still has the following disadvantages such as harsh synthesis conditions, cation mixing and poor thermal stability. A spherical fluorine modified gradient NCA is successfully prepared by a simple solid phase method. The F-modification NCA has a good spherical shape which shows a gradient distribution with high surface F and Al contents, and high nickel content in the core. XRD results reveal that F-modification NCA sample has well-ordered layer structure. However, there is a slight decrease in the cell parameters and interlayer spacing with the F doping into the NCA crystal lattice, due to the small F − radius and the largest electronegativity. Energy Dispersive X-Ray Spectroscopy (EDX) analysis reveals that fluorine ions are successfully substituted in the lattice. The cycling stability of the F-modification NCA samples are enhanced, especially at high rates. At 2C rate, the initial discharge specific capacity is 142.34 mAh g −1 , and compared with that of 107.73 mAh g −1 after 200 cycles, the capacity losses only 24%. Electrochemical impedance spectroscopy (EIS) further indicates that F-modification could help inhibit the increasing of polarization and change the kinetics of NCA cathode.