Synthesis, characterization and electrochemical performance of AlF3-coated Li1.2(Mn0.54Ni0.16Co0.08)O2 as cathode for Li-ion battery
(School of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China)
Abstract: Li-rich layered transitional metal oxide Li1.2(Mn0.54Ni0.16Co0.08)O2 was prepared by sol-gel method and further modified by AlF3 coating via a wet process. The bare and AlF3-coated Li1.2(Mn0.54Ni0.16Co0.08)O2 samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and high resolution transmission electron microscope (HRTEM). XRD results show that the bare and AlF3-coated samples have typical hexagonal α-NaFeO2 structure, and AlF3-coated layer does not affect the crystal structure of the bare Li1.2(Mn0.54Ni0.16Co0.08)O2. Morphology measurements present that the AlF3 layer with a thickness of 5-7 nm is coated on the surface of the Li1.2(Mn0.54Ni0.16Co0.08)O2 particles. Galvanostatic charge-discharge tests at various rates show that the AlF3-coated Li1.2(Mn0.54Ni0.16Co0.08)O2 has an enhanced electrochemical performance compared with the bare sample. At 1C rate, it delivers an initial discharge capacity of 208.2 mA？h/g and a capacity retention of 72.4% after 50 cycles, while those of the bare Li1.2(Mn0.54Ni0.16Co0.08)O2 are 191.7 mA？h/g and 51.6 %, respectively.
Key words: lithium-ion battery; Li1.2(Mn0.54Ni0.16Co0.08)O2; AlF3 surface coating; capacity retention