LHCEs are a subset of highly concentrated electrolytes (HCEs), which are distinguished by their inherent lack of free solvent molecules. The ubiquity of coordinated solvent molecules in HCEs inhibits the electrolyte from participating in side reactions. For example, it has previously been shown that the use of LiFSI-based HCEs in iron fluoride batteries leads to a stable passivation layer that hinders active material dissolution, ion leaching, and Li dendrites. LHCEs are formed by diluting an HCE with a component that has little to no solubility with the electrolyte salt (e.g., a diluent). In this way, LHCEs retain the beneficial solvent structure of HCEs, while diminishing their drawbacks (e.g., high viscosity/cost and inferior wetting properties). Recently, our group showed that the particular LHCE used in the present report (vide infra) is stable with both Li metal and FeF3, enabling high CE and rate capability for Li-FeF3 batteries. Despite the beneficial properties of FeF3 (vide supra), commercialization of rechargeable Li-FeF3 batteries has been impeded by low CE, voltage hysteresis, slow kinetics, 1 low electronic conductivity, electrolyte decomposition, and volumetric changes during the conversion reaction. Use of an LHCE can address low CE and electrolyte decomposition. However, a more comprehensive strategy is needed to tackle the remaining challenges.