Li2TiO3 and Li2ZrO3 co-modification LiNi0.8Co0.1Mn0.1O2 cathode material with improved high-voltage cycling performance for lithium-ion batteries
Abstract LiNi0.8Co0.1Mn0.1O2 (NCM) materials with surface modification by Li2TiO3 (LTO), Li2ZrO3 (LZO) and Li2TiO3-Li2ZrO3 (LTZO) coatings are successfully synthesized via a simple wet chemical method and proper heat-treatment process. The crystal structure, surface morphology, valence states and electrochemical properties of different modified NCM materials are investigated by the means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The NCM co-modified by Li2TiO3 and Li2ZrO3 composite coatings (LTZO@NCM) shows remarkable improvements in cycling performance and rate capability, the discharge capacity is 190.36 mAh g−1 with high capacity retention of 92.64% at 0.2C after 100 cycles between 2.75 and 4.4 V, compared to 174.83 mAh g−1 with the capacity retention of 87.20% for pristine NCM. Even at a high current density of 1 C, LTZO@NCM still maintains a high discharge capacity of 149.77 mAh g−1 cycled at high cut-off voltage of 4.4 V, with a capacity retention rate of 83.04% at 150th cycle, while bare NCM only delivers 123.92 mAh g−1 with capacity retention of 68.86%. The enhanced electrochemical performance can be ascribed to the modified effect of LTZO nano-coating layer on the NCM surface. LTZO nano-coating layer can not only effectively protect NCM particles, avoid the occurrence of side reaction, but also provide a better Li+ transport channels, improve lithium ion diffusion rate and enhance the structure stability and electrochemical performances of NCM material.