Boosting the electrochemical performance of LiNi0.6Mn0.2Co0.2O2 through a trace amount of Mg-B co-doping

The extended cycle life of cells is often sacrificed at the expense of high specific energy for high-nickel materials. Cation doping is a promising method to build high-nickel cathode with high energy density and long cycle life. Herein, a trace amount of Mg-B co-doping in LiNi0.6Mn0.2Co0.2O2 (NMC622) is investigated in this work, which shows improved structural and electrochemical stability of 1% Mg-0.5 % B co-doped material at both 30 and 55 degrees C in coin-cell. Comprehensive chemical composition, structural, and surface analysis are carried out in this paper. It was found that all the selected materials have a similar composition to the target. Moreover, Mg and B doping have different effects on the crystal structural change of NMC622, to be more specific, the c-lattice parameter increases with Mg doping, while the Li+/Ni2+ mixing content increases when B was incorporated into the lattice. Furthermore, the microstructure of primary particles was changed by B doping significantly as confirmed by the SEM images. There were marginal benefits in terms of structural and electrochemical stability of materials introduced by Mg or B sole doping. In comparison, incorporating a suitable amount of both Mg and B into NMC622, we found the capacity retention of cells was noticeably improved by reducing the impedance growth and preventing cation mixing during cycling. This study demonstrates the importance of co-incorporation of Mg, B, and optimizing the co-dopant content to stabilize NMC622 as cathode for lithium-ion batteries. (C) 2021 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

This study demonstrates that incorporating a suitable amount of both Mg and B into NMC622 can significantly improve the capacity retention of cells, reduce impedance growth, and prevent cation mixing during cycling.