Separately In-situ Al2O3-coated and F-doped modifying on Li1.2Mn0.54Ni0.13Co0.13O2 cathode material to achieve high performance

With high capacity and working voltage, Li-rich Mn-based cathode materials are considered to be as the promising cathode materials for lithium-ion battery. In this study, Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ (LMO) is prepared by a co-precipitation method and two-step calcination process, and then the technologies of in-situ Al₂O₃-coated by alcohol hydrolysis and F-doped through solid-phase sintering are separately adopted to modify LMO. The results show that LMO possesses the layered structure of α-NaFeO₂ and the initial discharge capacity is high with 259.4 mAh g⁻¹. For Al₂O₃-coated cathode material (LMO@Al₂O₃), the coating-layer with 15–20 nm is successfully presented on the surfaces of particles while almost keeping the original microstructure and shape. The initial discharge capacity of LMO@Al₂O₃ is the highest with 266.1 mAh g⁻¹, after 100 cycles the capacity retention rate is the largest with 88.7 %, and at 0.5 C the discharge capacity is the best with 242 mAh g⁻¹. About F-doped cathode material (LMO-F), the particle shape is from sphere to polygon, the interlayer spacing is increased obviously, the tap density is the biggest with 2.88 g cm⁻³, and Li⁺ diffusion coefficient is up to 5.794$\times$10⁻¹² cm² s⁻¹. LMO-F exhibits an excellent capacity retention rate of 77.8 % after 200 cycles, and at 5 C the discharge specific capacity is 116 mAh g⁻¹. As can be seen separately modifications using in-situ Al₂O₃-coated and F-doped are the effective strategies to improve LMO, with which are the respective advantages in microstructure and electrochemical performance, and can meet the needs of different applications for cathode materials.