The Impact of Chemical Modifications on The Ionic Conductivity of Ionic Liquid Encapsulated in Carbon Nanotubes, Potential Application in Aluminum Ion Battery

Abstract

The transport and thermodynamic properties of 1-ethyl-3methyl imidazolium hexafluorophosphate ([EMIM][PF6]) ionic liquid encapsulated in carbon nanotubes or graphite represent a significant challenge in the development of Aluminum-ion batteries. To achieve high energy density in Aluminum-ion batteries, it is explored the use of ionic liquid solvents as electrolytes to enhance the ionic conductivity of the ionic liquid when encapsulated in carbon nanotubes as electrodes. The doping effects of sulfur and boron atoms in single-walled carbon nanotubes (SWCNTs) have been investigated to determine their impact on the ionic transfer number of the ionic liquid encapsulated in SWCNTs. The Green-Kubo formalism has been employed to calculate the ionic transfer number and electrical conductivity of the ionic liquid when encapsulated in SWCNTs doped with sulfur and boron atoms. The results obtained using the Green-Kubo formalism indicate that sulfur doping in SWCNTs, particularly in those with a larger radius, serves as a selective porous electrode material, significantly enhancing the electrical conductivity of the confined ionic liquid. Furthermore, the radial distribution function between the carbon alkyl groups in the ionic liquid and the carbon wall of the carbon nanotube, which is doped with sulfur and boron atoms, demonstrates that the doping effect does not alter the radial distribution function. The Green-Kubo result obtained for the electrical conductivity of the ([EMIM][PF6]) ionic liquid demonstrates excellent agreement with the experimental data.