Polydopamine-assisted coating layer of a fast Li-ion conductor Li6.25La3Zr2Al0.25O12 on Ni-rich cathodes for Li-ion batteries

Ni-rich cathode materials have promising applications in lithium-ion batteries owing to their high energy density and reasonable cost. The surface stabilization of these materials is vital for achieving excellent electrochemical performance. In this study, a fast ionic conductor, Li6.25La3Zr2Al0.25O12 (LLZAO), was successfully coated on the surface of LiNi0.88Co0.05Mn0.07O2 (LNCM) using a polydopamine (PDA) modification method. The abundant catechol groups of the intermediate PDA layer on the Ni0.88Co0.05Mn0.07(OH)2 (NCM(OH)2) precursor attracted metal ions in an aqueous solution, and a uniform LLZAO coating layer was formed after calcination under an O2 flow. The presence of the LLZAO protective film on the surface of LNCM was confirmed using several characterization techniques. The LLZAO-coated LNCM exhibited superior electrochemical properties compared to those of the pristine LNCM. Moreover, the LLZAO-coated LNCM demonstrated excellent electrochemical stability even at a high temperature (60 ℃). The deterioration of the surface structure of LNCM was significantly suppressed by the formation of the LLZAO coating layer, and LLZAO improved the Li+ ion transport at the electrode/electrolyte interface.