Fig. 8. (a) Formation energies ΔE and free energies ΔG for various lithium ion clusters calculated at the PBE/6-31+G(d,p) level of theory. In all cases except those involving TEGDME, the total coordination number has been constrained to four, while for TEGDME also higher coordination numbers as determined from the geometry optimization (see Fig. S1†) have been taken into account. For clusters involving TEGDME, a correction based on the energy differences between PBE and G4MP2 calculations has been applied (see Table S1† and main text). As a reference, we chose the [Li(EC)4]+ cluster modelling a lithium ion fully solvated by carbonate molecules. Snapshots of the [Li(TFSI)(MMA)2] and [Li(TFSI)2(MMA)2]− clusters that partially immobilize cations and anions are shown in (b) and (c), respectively.
