Improved electrochemical properties of nickel-rich cathode with aluminum‑titanium doping and lithium phosphate coating

Abstract

Nickel-rich LiNixCoyMnzO2 (x ≥ 80%) cathode materials have good commercial prospects in lithium-ion batteries because of high energy density. However, defects in Ni-rich cathodes, which arise from structural instability and surface erosion by electrolyte during the charge/discharge processes, impair electrochemical performance. We propose a simple co-precipitation and in situ coating method to form aluminum‑titanium co-doped, Li3PO4-coated LiNi0.83Co0.11Mn0.06O2 (NCM) material to eliminate defects in Ni-rich cathodes. Transmission electron microscopy and X-ray diffraction suggested that a 4-nm thick film was formed on the surface of NCM particles. The electrochemical properties of the modified NCM material were improved: (i) NCMAl0.3xTi1.7x@(Li3PO4)3x (x = 0.0036) achieved a specific discharge capacity of 166.4 mAh g−1 after 100 charge/discharge cycles, compared with the discharge capacity of 125.8 mAh g−1 for unmodified NCM. The retention rate was enhanced from 72.4% for NCM to 91.0% for modified NCM. (ii) The modified NCM had a higher initial discharge capacity from 81.3% to 87.9% and improved cyclic stability, lower Li+/Ni2+ cation mixing, and higher ionic conductivity.