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 Al2O3-coated cathode material shows enhanced electrochemical performance at a high operating voltage (4.5 V). These Al2O3 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 Al2O3-coated cathode materials exhibit better rate performance at low currents. The stable-phase alumina (alpha-Al2O3)-coated cathode material shows the best cycling stability with a capacitance retention of 85.1% after 100 cycles at 5C under 45 degrees C. And the alpha/theta-mixed-phase Al2O3-coated Nickel-rich cathodes (NCM) achieves excellent rate performance and cycling stability.