期刊
ACS APPLIED MATERIALS & INTERFACES
卷 13, 期 6, 页码 7308-7316出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsami.0c21501
关键词
high voltage; tungsten; lithium-ion battery; LiNi0.6Co0.2Mn0.2O2 cathode; doping
资金
- National Natural Science Foundation of China [22075051]
- Science and Technology Commission of Shanghai Municipality [19Dz2270100]
This study focuses on enhancing the thermal stability and electrochemical performance of LiNi0.6Co0.2Mn0.2O2 (NCM622) through W-doping. Experimental and theoretical calculations show that W-doping is most favorable at Co sites, helping to suppress oxygen release and improve structural stability. In addition, W-doping reduces the energy barrier for Li+ migration and enhances lithium ion diffusion.
More and more attention has been focused on Ni-rich ternary materials due to their superior specific capacity, but they still suffer inherent structural irreversibility and rapid capacity degradation under a high voltage. Oxidation of unstable oxygen will lead to the irreversible transformation of the structure. Taking into account the strong W-O bond, an appropriate amount of W-doping is studied to reinforce the thermal stability and electro-chemical performance of LiNi0.6Co0.2Mn0.2O2 (NCM622) at 4.5 V. Combining experiments and theoretical calculations, it can be found that W-doping is most preferred at Co sites, and the average charge around O in the NiO6 octahedron becomes more negative after W-doping, which can successfully restrain the release of oxygen, thereby improving the stability of the crystal structure during deep delithiation. In addition, W-doping decreases the energy barrier of the Li+ migration slightly and boosts the kinetic diffusion of lithium ions. As a result, NCM622 doped with 0.5% W boasts an outstanding capacity retention of 96.7% at 1 C after 100 cycles and a discharge specific capacity of up to 152.8 mA h g(-1) at 5 C between 3.0 and 4.5 V. Furthermore, analysis of the cycled electrodes indicates that the lattice expansion and the formation of microcracks during long cycling are suppressed after W-doping, thereby elevating the structure and interface stability. Therefore, doping an appropriate amount of W via simple methods is helpful to obtain Ni-rich cathode materials with admirable performance.
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