Flexible carbon fiber based structural supercapacitor composites with solvate ionic liquid-epoxy solid electrolyte

Accelerated lithium-ion diffusion via a ligand ‘hopping’ mechanism in lithium enriched solvate ionic liquids

“…The gradient pulse duration d was fixed at 2.0 ms, and maximum gradient strength and diffusion observation time were optimised for each sample. For 1 H, maximum gradient strength was chosen between 3 and 27 Tm À1 , with diffusion observation time (D) between 25 and 110 ms. For 19 F, maximum gradient strength was chosen between 5 and 27 Tm À1 , with diffusion observation time (D) between 25 and 130 ms. For 7 Li, maximum gradient strength was chosen between 10 and 29.7 Tm À1 , with diffusion observation time (D) between 25 and 750 ms. Repetition time was 1.00 s for 1 H and 19 F nuclei and between 1.00 and 1.46 for 7 Li nuclei.…”

“…11 SILs have been used as electrolytes in LIBs, [13][14][15][16] as a sizing agent for carbon fibre in structural composites, 17 as reaction media, 1,18 and in bicontinuous electrolyte systems in structural supercapacitors. 19 Fig. 1 Generalised reaction scheme and structures of G3 (a) and G4 (b).…”

“…[35][36][37][38][39][40][41][42] As mentioned previously, increasing lithium concentration in SILs increases viscosity, 20 so the benefits of increased ion concentration during supercapacitor charging may come at a cost to reduced ion mobility in higher viscosity solutions. Ueno et al previously investigated 1 : 1 G3 : LiTFSI and G4 : LiTFSI physical properties including 7 Li, 1 H, and 19 F rates of selfdiffusion at 30 1C, ionic conductivity and thermal properties. 43 Findings showed that [Li-G3]TFSI had a higher viscosity (169 mPa s) compared to [Li-G4]TFSI (81 mPa s).…”

“…The t Li values for 1 : 1 G3 : LiTFSI and G4 : LiTFSI were 0.6 and 0.52, respectively, while the selfdiffusion coefficients were D Li 0.89, D H 0.84 & D F 0.57 for G3 and D Li 1.31, D H 1.29 & D F 1.22 for G4 (all of the same magnitude, Â 10 À7 cm 2 s À1 ). 43 Yoshida et al has previously investigated sub-stoichiometric lithium salt ratios, increasing concentrations of ether solvents in a range from 400 : 1 to 1 : 1 (G3/G4 : LiTFSI) and reported 7 Li, 1 H, and 19 F rates of self-diffusion, viscosity and ionic conductivity at 30 1C. 20,43 In that work, viscosity increased with increasing LiTFSI concentration, while ionic conductivity peaked, at B3.7(G3) and 3.3(G4) mS cm À1 , at approximately 4 : 1 G3/G4 : LiTFSI and decreased to B1.6(G3) and 1(G4) mS cm À1 , values similar to 1 : 1 ratios reported by Ueno et al Self-diffusion of ethereal solvents was B60% faster than Li + & TFSI À for higher solvent ratios and approximately equal for 1 : 1 ratios.…”

“…The glyme : LiTFSI stoichiometries examined here are 1 : 4 and 1 : 3.5, for G3, 1 : 1.75 and 1 : 1.25 for G4, and 1 : 3, 1 : 2.5, 1 : 2, 1 : 1.5 and 1 : 1 for G3 and G4, for context and comparison to literature values. We report the self-diffusion properties of 7 Li, 1 H, and 19 F nuclei, and Li + transference numbers, present in G3/G4 : LiTFSI samples over a temperature range, 20-80 1C, relevant to their application as electrolytes in energy storage applications. 10 To complement those data, ion mobility, thermal stability and thermal phase state are also presented to provide context on how these materials handle and can be processed.…”