The effect of surface modification on high capacity Li_1.375Ni_0.25Mn_0.75O_2+γ cathode material for lithium-ion batteries

Highlights: • Li_1.375Ni_0.25Mn_0.75O_2+γ is coated with AlF₃ layer via a simple chemical deposition. • A spinel-like component is detected on its surface after modified by AlF₃. • The AlF₃ modification sample exhibits high initial coulombic efficiency of 93.6%. • AlF₃ coating layer can suppress the increase of R_ct during cycling. - Abstract: Li_1.375Ni_0.25Mn_0.75O_2+γ exhibits an obviously enhanced electrochemical performance after AlF₃ surface modification, including the high initial discharge capacities of 276.8 mA h g⁻¹ and high coulombic efficiency of 93.6%. The results from powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma (ICP) and galvanostatical test confirm that its electrochemical improvement can be mainly attributed to the appearance of spinel-like structure on the surface of the layered material induced by AlF₃-modified. Moreover, the reduced charge transfer resistance (R_ct) during cycling contributes to a better cycle stability of AlF₃-modified Li_1.375Ni_0.25Mn_0.75O_2+γ