Structural comparisons of fast ion conductors consisting of Li[(CF3SO2)2N] complexes with cryptands or crown ether

Plastic crystalline phases of crown ether:salt complexes and their utilization in lithium-metal batteries

“…This complex exhibited an ionic conductivity of 8.3 × 10 −6 Scm −1 at 20 • C, that increased to 6.1 × 10 −5 Scm −1 at 40 • C (in the plastic crystal phase), and to 1.8 × 10 −4 Scm −1 at 50 • C (above melting). These values are lower than the ones reported by Shriver et al [8] who obtained, for example, a conductivity of 3.5 × 10 −5 at 20 • C. In general, the variation of conductivity with temperatures follows the binomial behavior already reported for other plastic crystals [14].…”

“…The cells were cycled in a potentiostatic mode between 3 and 3.7 V at 40 • C. When the molar ratio was varied from 1/1 to 1/0.95 in order to introduce ion-free crown ether rings, the DSC scan showed only a slight decrease of the melting point from 145 to 134 • C. However, when the ratio was changed to 1/0.6, 1/0.5 and 1/0.4, a completely different behavior was encountered. In this case, the peak at ∼−110 • C disappeared in all the three compounds, while another appeared at ∼105 • C, that is, most probably, attributable to the formation of a 2/1 complex [8]. It is also observed that the peak at 89 • C of the 1/1 decreased as a function of ratio to reach 67 • C at 1/0.4.…”

Structural Diversity in Lewis‐Base Complexes of Lithium Triflamide

“…The presence of two TAC ligands around the lithium ion provides sufficient steric protection to preclude any cation-anion interactions in 5. ϩ cation are shown as wire frames and hydrogen atoms omitted for clarity; selected bond lengths (Å ): Li(1)ϪN (1) 2.2411(15), Li (1)ϪN(2) 2.2602(15), Li(1)ϪN (3) 2.2471(16), S(1)ϪN (7) 1.5731 (17), S(2)ϪN (7) 1.5736(18), S(1)ϪO (1) 1.4259(16), S(1)ϪO (2) 1.4239(15), S(2)ϪO (3) 1.4286(15), S(2)ϪO (4) 1.4223(15); selected bond angles (°): N(1)ϪLi (1)ϪN(2) 63.64 (6), N(1)ϪLi (1)ϪN(3) 63.53 (6), N(2)ϪLi (1)ϪN(3) 63.06(6), S(1)ϪN (7)ϪS (2) [26] [Li(C-2,2,2)][NTf 2 ], [26] [Mg(H 2 O) 6 ][NTf 2 ] 2 , [27] [Im][NTf 2 ], [28] [R 4 N][NTf 2 ] [29] and [Me 3 NH][NTf 2 ]. [30] It is noteworthy that even using the high degree of control provided by the ammonium salt route, it has not been possible to isolate mono Bz-TAC complexes, such as [(iPr- [24] highlighting the high stability of the [(Bz-TAC) 2 Li] ϩ cation.…”

Spectroscopic characterization of the conformational states of the bis(trifluoromethanesulfonyl)imide anion (TFSI−)

“…It is known, for example, that the anion adopts the transoid form in the G1 1 : LiTFSI and 12-crown-4 2 : LiTFSI complexes. 6,7 The latter compound is particularly interesting because the Li C cation is sandwiched between two crown ether ligands and does not establish any direct coordination with the anion. 6 Unfortunately, cisoid conformations are rare and are stabilized in systems such as KTFSI, 3 H 2 O 1 : LiTFSI 4 and 1,3dimethylimidazolium-TFSI, 8 where ionic interactions may produce stronger spectral changes than the conformational effect itself.…”

“…1). 1 Several structural studies of alkali metal salts, either pure, 2 -4 dissolved in polymers such as poly(ethylene oxide) (PEO) 5 or complexed by small ether molecules, 6,7 have confirmed that the anion adopts either the transoid or the cisoid form. Recent structural studies of imidazolium salts have also found the TFSI anion in one of these two forms, depending on the substitution on the imidazolium ring.…”