Suppressing irreversible phase transition and enhancing electrochemical performance of Ni-rich layered cathode LiNi0.9Co0.05Mn0.05O2 by fluorine substitution

Ni-rich layered oxide LiNixCoyMn1-x-yO2 (x >= 0.8) is the most promising cathodes for future high energy automotive lithium-ion batteries. However, its application is hindered by the undesirable cycle stability, mainly due to the irreversible structure change at high voltage. Herein, we demonstrate that F substitution with the appropriate amount (1 at%) is capable for improve the electrochemical performance of LiNi0.9Co0.05Mn0.05O2 cathode significantly. It is revealed that F substitution can reduce cation mixing, stabilize the crystal structure and improve Li transport kinetics. The resulted LiNi0.9Co0.05Mn0.05O1.99F0.01 cathode can deliver a high capacity of 194.4 mAh g(-1) with capacity retention of 95.5% after 100 cycles at 2C and 165.2 mAh g(-1) at 5C. In-situ synchrotron X-ray technique proves that F ions in the cathode materials can suppress the irreversible phase transition from H2 phase to H3 phase in high voltage region by preventing oxygen gliding in a-b planes, ensuring a long-term cycle stability. (C) 2021 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

Automated summary

The electrochemical performance of Ni-rich layered oxide can be significantly improved by appropriate F substitution, reducing cation mixing, stabilizing crystal structure, and enhancing Li ion transport kinetics. The newly developed LiNi0.9Co0.05Mn0.05O1.99F0.01 cathode exhibits high capacity and excellent cycle stability.