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Unraveling the role of structural water in bilayer V2O5 during Zn2+-intercalation: insights from DFT calculations

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Abstract

Bilayer structured V2O5·nH2O has recently been studied as a promising cathode material for aqueous Zn2+-batteries (ZIBs) due to its ion-intercalatable layer structure and high theoretical capacity. An interesting observation in this system is the beneficial effect of structural water (nH2O) on the electrochemical performance, but a fundamental understanding of the underlying reason is still lacking. Herein, we report a systematic density functional theory investigation into why and how structural water in the bilayer V2O5·nH2O affects the structure, voltage, migration barrier and capacity during the Zn2+-intercalation process. The results suggest that the structural water acts as extra host sites to accept electrons from Zn, resulting in stronger ionization of Zn2+ than that on dry V2O5 and thus a higher open-circuit voltage (OCV). It is also found that structural water creates a smoother electrostatic environment between V2O5 sheets for easy Zn2+ diffusion. Benefitting from the combined “charge shielding” and “O in H2O interaction with Zn2+” effect, V2O5·H2O and V2O5·1.75H2O exhibit lower Zn2+-diffusion barriers and higher OCVs than non-hydrated V2O5. Overall, this DFT study provides mechanistic insights into the importance of structural water in promoting the Zn2+-intercalation process in bilayer V2O5.

Graphical abstract: Unraveling the role of structural water in bilayer V2O5 during Zn2+-intercalation: insights from DFT calculations

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Publication details

The article was received on 13 Dec 2018, accepted on 10 Feb 2019 and first published on 11 Feb 2019


Article type: Paper
DOI: 10.1039/C8TA12014E
Citation: J. Mater. Chem. A, 2019, Advance Article

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    Unraveling the role of structural water in bilayer V2O5 during Zn2+-intercalation: insights from DFT calculations

    T. Wu, K. Zhu, C. Qin and K. Huang, J. Mater. Chem. A, 2019, Advance Article , DOI: 10.1039/C8TA12014E

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