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Mechanism of Sodium Ion Storage in Na₇[H₂PV₁₄O₄₂] Anode for Sodium-Ion Batteries

Lookup NU author(s): Professor Ulrich Stimming

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Abstract

© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. In this work, the authors explore the sodium salt of the 14-vanado(V)phosphate, Na7[H2PV14O42], as a potential anode material for sodium-ion batteries (NIBs). The multi-electron redox activity of the polyoxovanadate [H2PV14O42]7-leads to high capacity. This polyanion is synthesized by a simple aqueous solution procedure and isolate as a sodium salt with different numbers of crystal waters, Na7[H2PV14O42]·nH2O (n = 15-24). Na7[H2PV14O42] as anode in NIBs exhibits a high and reversible capacity of 322 mA h g-1 at 25 mA g-1 with a high cycling stability (with capacity retention of 87% after 120 cycles). Some of the V5+ ions in [H2PV14O42]7- can be reduced to V3+ after being discharged to 0.01 V versus Na/Na+, resulting in an average oxidation state of V3.7+, as based on ex situ X-ray photoelectron spectroscopy and in situ synchrotron X-ray absorption near edge structure studies. The crystalline material becomes amorphous during the charge/discharge processes, which can be observed by in situ synchrotron X-ray diffraction, indicating that functionality does not require crystallinity. The authors propose that the charge storage mechanism of Na7[H2PV14O42] anodes mainly involves redox reactions of V accompanied by insertion/extraction of Na ions in-between polyoxo-14-vanadate ions and adsorption/desorption of Na ions on the surface of the vanadate material.

Publication metadata

Author(s): Lin C-C, Lin W-H, Huang S-C, Hu C-W, Chen T-Y, Hsu C-T, Yang H, Haider A, Lin Z, Kortz U, Stimming U, Chen H-Y

Publication type: Article

Publication status: Published

Journal: Advanced Materials Interfaces

Year: 2018

Volume: 5

Issue: 15

Print publication date: 09/08/2018

Online publication date: 04/07/2018

Acceptance date: 02/04/2018

ISSN (electronic): 2196-7350

Publisher: Wiley-VCH Verlag

URL: https://doi.org/10.1002/admi.201800491

DOI: 10.1002/admi.201800491

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