Ion interactions and dynamics in pseudohalide based ionic liquid electrolytes containing sodium solutes

TY - JOUR

T1 - Ion interactions and dynamics in pseudohalide based ionic liquid electrolytes containing sodium solutes

AU - Hilder, Matthias

AU - Pointu, Tony

AU - Zhu, Haijin

AU - Armand, Michel

AU - Howlett, Patrick

AU - Forsyth, Maria

N1 - Publisher Copyright: © 2020

PY - 2020/4/1

Y1 - 2020/4/1

N2 - Sodium batteries have been identified as a promising, inexpensive technology for future energy storage applications. However, while an optimum electrolyte is key to a high performance device, sodium electrolytes are still at an early stage of development. Recently we explored the cycling behavior of a series of electrolytes based on a readily available dicyanamide-based ionic liquid with various sodium salts added based on fluorinated anions in order to improve sodium electrochemistry. Herein we focus on the structure and ion dynamics in the bulk electrolyte. Electrolyte solutions of 1-methyl,1-propyl pyrrolidinium dicyanamide (C3mpyDCA) and 1-methyl,1-butyl pyrrolidinium tricyanomethanide (C4mpyTCM) with various sodium salts were studied in order to understand the effect of solute anion on physicochemical behavior, in particular phase behavior, ion dynamics and inter-ionic interactions. For the DCA systems strong Na+-DCA− interactions dominate. The expectation that switching to the TCM anion would see a weakening in the electrostatic interactions (due to a higher degree of charge delocalization and larger size ion) was not observed. Indeed the TCM systems led to less salt solubility, lower ionic conductivity and greater deviation from the Walden ideal KCl line. We use infrared and NMR spectroscopies to investigate ion-ion interactions and it appears that the nitrile anion dominates the Na coordination environment for both DCA and TCM ionic liquid systems.

AB - Sodium batteries have been identified as a promising, inexpensive technology for future energy storage applications. However, while an optimum electrolyte is key to a high performance device, sodium electrolytes are still at an early stage of development. Recently we explored the cycling behavior of a series of electrolytes based on a readily available dicyanamide-based ionic liquid with various sodium salts added based on fluorinated anions in order to improve sodium electrochemistry. Herein we focus on the structure and ion dynamics in the bulk electrolyte. Electrolyte solutions of 1-methyl,1-propyl pyrrolidinium dicyanamide (C3mpyDCA) and 1-methyl,1-butyl pyrrolidinium tricyanomethanide (C4mpyTCM) with various sodium salts were studied in order to understand the effect of solute anion on physicochemical behavior, in particular phase behavior, ion dynamics and inter-ionic interactions. For the DCA systems strong Na+-DCA− interactions dominate. The expectation that switching to the TCM anion would see a weakening in the electrostatic interactions (due to a higher degree of charge delocalization and larger size ion) was not observed. Indeed the TCM systems led to less salt solubility, lower ionic conductivity and greater deviation from the Walden ideal KCl line. We use infrared and NMR spectroscopies to investigate ion-ion interactions and it appears that the nitrile anion dominates the Na coordination environment for both DCA and TCM ionic liquid systems.

KW - DCA

KW - Electrolytes

KW - Energy storage

KW - Intermolecular interactions

KW - Ionic liquids

KW - Sodium batteries

KW - TCM

UR - http://www.scopus.com/inward/record.url?scp=85079902631&partnerID=8YFLogxK

U2 - 10.1016/j.molliq.2020.112597

DO - 10.1016/j.molliq.2020.112597

M3 - 文章

AN - SCOPUS:85079902631

SN - 0167-7322

VL - 303

JO - Journal of Molecular Liquids

JF - Journal of Molecular Liquids

M1 - 112597

ER -