Two phosphonium ionic liquids with high Li+ transport number

Author(s)

Martins, Vitor L. ^[1] ; Sanchez-Ramirez, Nedher ^[1] ; Ribeiro, Mauro C. C. ^[1] ; Torresi, Roberto M. ^[1]

Affiliation

^[1] Univ Sao Paulo, Inst Quim, BR-05513970 Sao Paulo, SP - Brazil

• Document type: Journal article
• Source: Physical Chemistry Chemical Physics; v. 17, n. 35, p. 23041-23051, 2015.
• Web of Science Citations: 20

Abstract

This work presents the physicochemical characterization of two ionic liquids (ILs) with small phosphonium cations, triethylpenthylphosphonium bis(trifluoromethanesulfonyl)imide ({[}P-2225]{[}Tf2N]) and (2-methoxyethyl)trimethylphosphonium bis(trifluoromethanesulfonyl) imide ({[}P-222(201)]{[}Tf2N]), and their mixtures with Li+. Properties such as the electrochemical window, density, viscosity and ionic conductivity are presented. The diffusion coefficient was obtained using two different techniques, PGSE-NMR and Li electrodeposition with microelectrodes. In addition, the Li+ transport number was calculated using the PGSE-NMR technique and an electrochemical approach. The use of these three techniques showed that the PGSE-NMR technique underestimates the diffusion coefficient for charged species. The Li+ transport number was found to be as high as 0.54. Raman spectroscopy and molecular dynamics simulations were used to evaluate the short-range structure of the liquids. These experiments suggested that the interaction between the Li+ and the Tf2N- anion is similar to that seen with other ILs containing the same anion. However, the MD simulations also showed that the Li+ ions interact differently with the cation containing an alkyl ether chain. The results found in this work suggest that these Li+ mixtures have promising potential to be applied as electrolytes in batteries. (AU)

• FAPESP's process: 14/01987-6 - Study of lithium intercalation into different nanostructured cathode based on oxides of transition metal using ionic liquid (ILs) with low viscosity synthesized from phosphonium and tetracyanoborate like electrolytes.
• Grantee: Nédher Sánches Ramírez
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 09/53199-3 - Molecular recognition and energy storage: fundamental studies concerning geometry, size and synthesis effects on the optimization of the chemical properties of electroactive materials
• Grantee: Roberto Manuel Torresi
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 13/22748-7 - Development of High Performance Electrochemical Capacitors Based on Graphene and Ionic Liquids.
• Grantee: Vitor Leite Martins
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 10/08646-9 - Synthesis and characterization of ionic liquids based in phosphonium quaternary cations
• Grantee: Nédher Sánches Ramírez
• Support Opportunities: Scholarships in Brazil - Doctorate