Overall, there are three important takeaways from Figure . First, the cycling performance obtained with gel-2 across a range of current densities (0.05-0.50 mA cm -2 ) matches that of the LHCE control. We reiterate that gel-2 has the added advantage of flexibility, which helps the cell adapt to the large volume changes expected during iron fluoride conversion reactions (up to 30%). Despite similar Li-FeF3 full cell performance at 0.05-0.50 mA cm -2 for gel-2 and the LHCE control, the capacities of the former are approximately half that of the latter at the fastest rate tested (1.0 mA cm -2 = 1 C; Figure ). We hypothesize that the gap in cycling performance at 1.0 mA cm -2 between gel-2 and the LHCE control is due to slower ion transport in the presence of the gel. For example, polymer gels have a tendency to be non-Newtonian and thus dependent on shear rate. Non-uniformity in gel thickness (e.g., as a result of the dropcasting procedure used here) can decrease Li + ion mobility. Although this discrepancy might be small enough to go undetected for gel-2 at slow rates (due to the low viscosity of the LHCE), it may become significant at faster rates (where ohmic losses and the demands of ion transport are greater).