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Issue 16, 2019
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First-principles study of NaxTiO2 with trigonal bipyramid structures: an insight into sodium-ion battery anode applications

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Abstract

Developing efficient anode materials with low electrode voltage, high specific capacity and superior rate capability is urgently required on the road to commercially viable sodium-ion batteries (SIBs). Aiming at finding a new SIB anode material, we investigate the electrochemical properties of NaxTiO2 compounds with unprecedented penta-oxygen-coordinated trigonal bipyramid (TB) structures by using first-principles calculations. Identifying the four different TB phases, we perform the optimization of their crystal structures and calculate their energetics such as sodium binding energy, formation energy, electrode potential and activation energy for Na ion migration. The computations reveal that the TB-I phase is the best choice among the four TB phases for a SIB anode material due to a relatively low volume change of under 4% upon Na insertion, low electrode voltage under 1.0 V with a possibility of realizing the highest specific capacity of āˆ¼335 mA h gāˆ’1 from full sodiation at x = 1, and reasonably low activation barriers under 0.35 eV at the Na content from x = 0.125 to x = 0.5. Through the analysis of electronic density of states and charge density difference upon sodiation, we find that the NaxTiO2 compounds in TB phases change from electron insulating to electron conducting materials due to the electron transfer from Na atoms to Ti ions, offering the Ti4+/Ti3+ redox couple for SIB operation.

Graphical abstract: First-principles study of NaxTiO2 with trigonal bipyramid structures: an insight into sodium-ion battery anode applications

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Publication details

The article was received on 15 Jan 2019, accepted on 26 Mar 2019 and first published on 27 Mar 2019


Article type: Paper
DOI: 10.1039/C9CP00267G
Citation: Phys. Chem. Chem. Phys., 2019,21, 8408-8417

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    First-principles study of NaxTiO2 with trigonal bipyramid structures: an insight into sodium-ion battery anode applications

    S. Choe, C. Yu, K. Ri, J. Kim, U. Jong, Y. Kye and S. Hong, Phys. Chem. Chem. Phys., 2019, 21, 8408
    DOI: 10.1039/C9CP00267G

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