Nanobelts of Beta-Sodium Vanadate as Electrode for Magnesium and Dual Magnesium-Sodium Batteries

Abstract

© The Author(s) 2016. Published by ECS. All rights reserved. Nanoparticles of sodium vanadate (composition approximately NaV 6 O 15 ) with nanobelt morphology and monoclinic structure (β-phase) were prepared by using the hydrothermal method, α-V 2 O 5 as vanadium source and sodium dodecyl sulfate as both surfactant and source of sodium. This material can reversibly accommodate lithium, sodium and magnesium in its framework. Sodium vanadate nanobelts exhibit lower capacity than V 2 O 5 in lithium and sodium cell. In sodium cell, the electrochemical performance with NaOTf-diglyme electrolyte solution was much better than with NaClO 4 -propylene carbonate solution. In the case of dual sodium-magnesium electrolyte, the presence of sodium in β-NaV 6 O 15 and the small particle size improve the electrochemical behavior and increase the capacity (125 mAh g -1 ) in comparison with α-V 2 O 5 (10 mAh g -1 ). The electrolyte solution based on Mg(BH 4 ) 2 and NaBH 4 dissolved in diglyme is compatible with Mg metal and yields to better electrochemical performance than magnesium perchlorate dissolved in acetonitrile. Both sodium and magnesium are reversibly intercalated at the positive electrode and electrodeposited at the negative electrode and, consequently, it can be described as a dual battery. On the other hand, a veritable magnesium-ion battery was made using MgMn 2 O 4 as positive electrode and NaV 6 O 15 as negative electrode, although the resulting operation voltage is low.