Suppressing the Voltage Fading of Li[Li0.2Ni0.13Co0.13Mn0.54]O2 Cathode Material via Al2O3 Coating for Li-Ion Batteries

Abstract

Lithium-rich layered material with the structure xLi2MnO3∙(1–x)LiMO2 (M = MnyNizCo1-y-z, 0≤y≤1, 0≤z≤1, 0≤y+z≤1) is a highly potential cathode candidate for lithium-ion batteries. However, the fading voltage during cycling has seriously hindered the further development of this material. In this study, Li[Li0.2Ni0.13Co0.13Mn0.54]O2 is synthesized through a co-precipitation method and modified by surface coating with Al2O3 layer via sol-gel method. Discharge voltage fading is observed and investigated. Results show that the discharge voltage fading of the pristine material is 0.33 V after 30 cycles, compared to 0.15 V of the Al2O3-coated sample. The average discharge voltage of the Al2O3-coated material is improved, but its deterioration rate is suppressed effectively during the charge/discharge cycling. The intrinsic mechanism is investigated by ex situ XRD, XPS, TEM, CV, and EIS analysis. Results indicate that the lower discharge voltage fading should be ascribed to less structural change, lighter grain coarsening, and smaller impedance variation of the Li-rich layered material after Al2O3 coating.