First-principles investigation on the structural, electronic properties and diffusion barriers of Mg/Al doped NaCoO sub(2) as the cathode material of rechargeable sodium batteries

Mg/Al doped NaCoO sub(2) layered transition-metal oxides as potential cathode materials for sodium ion batteries have been investigated by first-principle calculations. The effects of divalent Mg ion or trivalent Al ion doping on the crystal structure, electron transfer, the changes of valence, aver...

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Bibliographic Details
Published in:RSC advances 2015-03, Vol.5 (35), p.27229-27234
Main Authors: Su, Jingcang, Pei, Yong, Yang, Zhenhua, Wang, Xianyou
Format: Article
Language:English
Subjects:
Aluminum
Cathodes
Diffusion barriers
Doping
Electric potential
Magnesium
Mathematical analysis
Sodium
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Summary:Mg/Al doped NaCoO sub(2) layered transition-metal oxides as potential cathode materials for sodium ion batteries have been investigated by first-principle calculations. The effects of divalent Mg ion or trivalent Al ion doping on the crystal structure, electron transfer, the changes of valence, average intercalation voltage and diffusion barriers of NaCoO sub(2) are studied. The DFT calculations indicate NaCoO sub(2) with Mg or Al ions doping will lead to a higher average intercalation voltage, which is beneficial for obtaining high energy density. Charge disproportionation induced by divalent Mg ion doping results in the appearance of electronic holes in Na(Co sub(0.92)Mg sub(0.08))O sub(2), which may enhance its conductivity significantly. The nudged elastic band calculation results indicate that trivalent Al ion doping has a slight effect on the diffusion barriers of NaCoO sub(2), but divalent Mg ion doping can significantly decrease the diffusion barriers and enhance the Na ion diffusion rate, which is beneficial to the improvement of the rate capability.
ISSN:2046-2069
DOI:10.1039/c5ra01895a