Figure shows that when 20 prior cycles are performed at slower rates, the average CE at 1.0 mA cm -2 for the gel-2 and LHCE control FeF3 half-cells (over 50 subsequent cycles) increases to 98 ± 3% and 99 ± 3%, respectively. These CEs are similar to those obtained for the Li-FeF3 full cells cycled with identical conditions (Figure ; 99 ± 3% and 98 ± 4%, respectively). Figure and Figure collectively demonstrate that although CEI buildup lags behind SEI buildup, ≥98% CE is ultimately obtained. High CE with both the Li half-cells and FeF3 half-cells suggests that gel-2 is stable with both the Li metal anode and the FeF3 cathode. Electrochemical rate testing. Figure compares Li-FeF3 rate testing for gel-1, gel-2, and an LHCE control (no gel) at current densities ranging from 0.05-0.50 mA cm -2 (= C/20 to C/2; five cycles each). Before discussing the main results, it is worth pointing out several features in the initial five cycles at 0.05 mA cm -2 . Briefly, the slightly greater than theoretical (712 mAh g -1 ) initial discharge capacities and steep capacity drop between the first and second cycles (~14-19%) are believed to be due to CEI formation in iron fluoride batteries. Furthermore, the downward sloping trend in the initial five cycles is consistent with our previous finding that Li-FeF3 capacity fade requires ~20-30 cycles at C/20 (or 0.05 mA cm in the present report) to stabilize in LHCE. Figure shows that cycle stability improves at higher current densities (0.10 to 1.0 mA cm -2 = C/10 to 1 C). As discussed in the previous section, Figure suggests that the number of initial cycles (rather than the particular current density) governs capacity fade stabilization. We note, however, that kinetic limitations could also play a role in stabilizing capacity fade at faster rates. For example, more reversible steps (e.g., the insertion step to form LixFeyF3) could be favored over kinetically sluggish steps (e.g., the conversion reaction) 1 at faster rates. Indeed, Figure and Table show that preference for the conversion reaction decreases by a small but significant (~7%) amount from 0.05 to 1.0 mA cm -2 .