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Roles of additives in the trihexyl(tetradecyl) phosphonium chloride ionic liquid electrolyte for primary mg-air cells

journal contribution
posted on 29.04.2014, 00:00 authored by Jenny Yan, Timothy KhooTimothy Khoo, Cristina Pozo-GonzaloCristina Pozo-Gonzalo, Anthony Hollenkamp, Patrick HowlettPatrick Howlett, D R MacFarlane, Maria ForsythMaria Forsyth
As reported previously, water saturated trihexyl(tetradecyl)phosphonium chloride ([P6,6,6,14][Cl]) ionic liquid (IL) is a promising electrolyte for magnesium-air batteries. The added water plays an important role in enabling high rate and high efficiency Mg dissolution while stabilizing the Mg interphase. In this work, the role of the water was investigated by replacement with other additives such as toluene and tetrahydrofuran to specifically target the assumed roles of water, namely: (i) enhancement of transport properties; (ii) complexation and stabilization of the Mg anode; (iii) provision of active protons for the cathodic reaction. Discharge tests show that ethylene glycol supports comparable performance to that provided by water. Examination of the viscosity and conductivity of different [P6,6,6,14][Cl]/additive mixtures indicates that a simple consideration of solution characteristics cannot explain the observed trends. Rather, other factors, such as the presence of active protons and/or oxygen-donor groups, are also key features for the development of IL electrolytes for practical magnesium-air cells. Finally, the presence of ethylene glycol in the electrolyte results in a complex gel on the Mg interface, similar to that found in the presence of water. This may also play a role in enabling stable discharge of the Mg anode. © 2014 The Electrochemical Society.

History

Journal

Journal of the Electrochemical Society

Volume

161

Issue

6

Pagination

A974 - A980

Publisher

Electrochemical Society Inc.

Location

NJ, United States

ISSN

0013-4651

eISSN

1945-7111

Language

eng

Publication classification

C Journal article; C1 Refereed article in a scholarly journal

Copyright notice

2014, Electrochemical Society, Inc.