For each TS, we confirmed that the optimized structure possessed one imaginary frequency and confirmed that it connected the expected endpoints. For cases where the endpoints consist of two molecules that are not covalently bound (typically bound only by coordination to Li + ), we allow small imaginary frequencies (less than 75i cm -1 ). These small imaginary modes can prove extremely difficult to remove using conventional geometry optimization methods, especially when they involve the motion of Li + ions, and typically do not significantly affect the free energy. We note that in some cases, the barriers that we report are based on the difference between the TS and the reactants or products at infinite separation, rather than the entrance or exit complex. The electronic energies of all optimized structures (TS and endpoints) were corrected using a single-point calculation at a higher level of theory (ωB97X-V/def2-TZVPPD/SMD) in Q-Chem. The SMD parameters used were the same used for the construction of the LIBE dataset. We note that we used Q-Chem for these calculations, rather than Jaguar, because the SMD implicit solvent model is not implemented in Jaguar at the time of this writing.