< BF 4 AN, MF 4 TFSI < AsF. < NO 3 THF 1 BPh 4 << SbF 6 < AsF PC, EMC, γ-bl 7,8 TFSI, AsF 6 < PF 6 < ClO 4 << BF. 4 < CF 3 SO 3 γ-bl 9 TFSI, AsF 6, PF

Transcription

1 1 Supporting Information: Glyme-Lithium Salt Phase Behavior Wesley A. Henderson Ionic Association Constants and Vibrational Spectroscopy Ionic association in solvent-salt electrolytes is typically studied by measuring ionic association constants, K A or K T (ion pair or triple ion formation constants, respectively), which may be obtained from fitting non-linear equations to molar conductivity Λ (S cm 2 mol -1 ) vs. salt concentration c (mol L -1 ) data. 1 Supp. Table 1 shows the typical ordering of increasing ionic association of LiX salts in aprotic solvents. Supp. Table 1 Increasing ionic association of LiX salts in aprotic solvents from reported calculated association constants. DMM 2,3 ClO 4 < SCN < BF 4 AN, MF 4 TFSI < AsF 6 << ClO 4 2-MeTHF 4,5 BPh 4 << AsF 6 << BF 4 THF 4,5 BPh 4 < AsF 6 << ClO 4 THF 6 ClO 4 << BF 4 << Br < NO 3 THF 1 BPh 4 << SbF 6 < AsF 6 << ClO 4 PC, EMC, γ-bl 7,8 TFSI, AsF 6 < PF 6 < ClO 4 << BF 4 < CF 3 SO 3 γ-bl 9 TFSI, AsF 6, PF 6 < ClO 4 PC 10 TFSI, AsF 6, PF 6 < ClO 4 < BF 4 < C 4 F 9 SO 3 < CF 3 SO 3 PC/G1 11 AsF 6, PF 6 < TFSI, ClO 4 << BF 4 < CF 3 SO 3 PC/G1 12 TFSI, AsF 6 < PF 6 < ClO 4 << BF 4 < CF 3 SO 3 THF, G1 13 AsF 6 << BF 4 G1 1 BPh 4 < SbF 6, AsF 6 < PF 6 << ClO 4 << BF 4 G AsF 6 << ClO 4 < BF 4 G1 17 ClO 4 < BF 4 < Br << Cl Propylene carbonate (PC), ethyl methyl carbonate (EMC), methyl formate (MF), 2-methyltetrahydrofuran (2- MeTHF), dimethoxymethane (DMM). Using vapor phase osmometry, Wong and Popov studied the association behavior of LiX and NaX salts in acetone and THF. 18 In acetone, LiBPh 4 is the most dissociated salt with LiI and LiClO 4 dissociated to a lesser extent. No appreciable dissociation occurred with LiNO 3, LiSCN and LiBr, while LiCl former higher aggregates. Association of the salts increased with increasing salt concentration (except for LiBPh 4 and NaBPh 4 ). In THF, however, all of the salts were associated to some extent, although the same general ordering for the salt association was noted. Goralski and Chabanel suggested the ordering according to the increasing degree of aggregation in weakly polar solvents 19 : LiClO 4 ~ LiI << LiSCN < LiBr << LiCl An IR spectroscopy study of the association of ions in acetonitrile (AN) n -LiX mixtures was done by analysing the band intensities of the AN molecules. 20,21 Association was found to increase in the order: LiI < LiClO 4 << LiSCN IR and Raman vibrational spectroscopy have also been extensively used to study ionic association in various solvent-lix solutions. The anion vibrational band frequencies change on coordination to one or more Li + cations. The observed anion vibrational bands for an electrolyte solution may therefore be attributed to specific forms of solvate species (SSIPs or 'free' anions, CIPs, AGGs). Ionic association in (G2) n -LiX mixtures has been studied with IR and Raman spectroscopy. Dilute (G2) n -LiNO 3 mixtures (EO/Li = 80) have a single Raman band at 25 C attributed to CIPs or possibly AGGs. For more concentrated mixtures (EO/Li = 20 and 5), a new band is found indicating the presence of more aggregated solvate species. 22 In (G2) n -LiSCN mixtures, the ions are associated almost entirely into CIPs (even at very low concentrations (EO/Li = 80) and low temperatures) with Li + cation coordination occurring through the nitrogen donor atom. There are no 'free' NO - 3 or SCN - anions in these glyme solutions. 22 At room temperature, (G2) n -LiCF 3 SO 3 mixtures consist of CIPs and AGGs with very few 'free' anions/ssips. 23 It should be noted, however, that upon cooling to -80 C, the EO/Li 6 mixtures show a 'free'

2 2 anion/ssip band (for the (G2) 2 :LiCF 3 SO 3 crystalline solvate). More concentrated (EO/Li = 4) mixtures have two bands corresponding to 'free' anions/ssips and AGGs (without CIPs). Two bands observed in (G2) n -LiBF 4 mixtures suggest the presence of both CIPs and 'free' BF - 4 anions/ssips. 22 (G2) n -LiClO 4 mixtures have both CIPs and 'free' ClO - 4 anions/ssips A single band for (G2) n -LiPF 6, (G2) n -LiAsF 6 and (G2) n -LiSbF 6 mixtures indicates that most of these anions are 'free'/ssips. 22,26-30 And finally, (G2) n -LiTFSI mixtures also consist predominantly of 'free' anions/ssips. 31,32 Supp. Fig. 1 Fractions of (THF) n -LiCF 3 SO 3 and (glyme) n -LiCF 3 SO 3 solvate species determined from literature vibrational spectroscopic studies of ionic association at (a) variable temperatures with a fixed concentration of EO/Li = 20 and (b) at a fixed temperature of 25 C with varying concentrations 22,23,33-40 (black - AGGs, gray - CIPs, white - SSIPs/free anions). Supp. Fig. 2 Fractions of (G2) n -LiClO 4 solvate species at (a) 70 C and varying concentration and (b) at varying temperatures for fixed concentrations determined from literature vibrational spectroscopic studies 26 (black - AGGs, gray - CIPs, white - SSIPs/free anions). Supp. Fig. 3 Fractions of (a) (G1) n -LiTFSI, (b) (G2) n -LiTFSI, (c) (G3) n -LiTFSI and (d) (G4) n -LiTFSI solvate species at room temperature determined from literature vibrational spectroscopic studies 31 (black - AGGs, gray - CIPs, white - SSIPs/free anions). Note that the AGG solvates in (c) and (d) may actually also include CIP solvates. From these literature publications (and given the difference in ionic association strength of the CCl 3 SO 3 and CCl 3 CO 2 anions, one can also conclude that CF 3 SO 3 << CF 3 CO 2 ), 41 the approximate ionic association strength ordering in aprotic solvents may be summarized as: BPh 4 < BETI, TFSI, SbF 6, AsF 6 < PF 6 < ClO 4, I < SCN < BF 4 < CF 3 SO 3 < Br < NO 3 < CF 3 CO 2

3 Supp. Fig. 4 DSC heating traces for (G1) n -LiX mixtures. 3

4 Supp. Fig. 5 DSC heating traces for (G1) n -LiX mixtures. 4

5 Supp. Fig. 6 DSC heating traces for (G2) n -LiX mixtures. 5

6 Supp. Fig. 7 DSC heating traces for (G2) n -LiX mixtures. 6

7 Supp. Fig. 8 DSC heating traces for (G3) n -LiX mixtures. 7

8 Supp. Fig. 9 DSC heating traces for (G3) n -LiX mixtures. 8

9 Supp. Fig. 10 DSC heating traces for (G4) n -LiX mixtures. 9

10 Supp. Fig. 11 DSC heating traces for (G4) n -LiX mixtures. 10

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