Coating Effect of Various-Phase Alumina Nanoparticles on NCM811 Cathode for Enhancing Electrochemical Performance of Lithium-Ion Batteries

Surface coating is a vital approach for addressing the aging of cathode materials in lithium-ion batteries. In this study, we synthesized various-phase alumina nanoparticles by subjecting boehmite to different temperatures and investigated the impact of these distinct alumina phases when used as a coating layer on the performance of nickel-rich cathode materials. Our findings demonstrate that any-phase Al 2 O 3 -coated cathode material shows enhanced electrochemical performance at a high operating voltage (4.5 V). These Al 2 O 3 coatings effectively inhibit the side reactions resulting from direct contact between the active material and electrolyte, reduce the dissolution of transition metal ions, and facilitate the formation of a uniform solid electrolyte interface (SEI). Notably, the sub-stable-phase Al 2 O 3 -coated cathode materials exhibit better rate performance at low currents. The stable-phase alumina (α-Al 2 O 3 )-coated cathode material shows the best cycling stability with a capacitance retention of 85.1% after 100 cycles at 5C under 45 °C. And the α/θ-mixed-phase Al 2 O 3 -coated Nickel-rich cathodes (NCM) achieves excellent rate performance and cycling stability.