By analogy to the Li half-cells, the stability of gel-2 with FeF3 was assessed by evaluating the average FeF3 half-cell CE over 50 cycles at 1.0 mA cm -2 (Figure ). The average FeF3 half-cell CE using these conditions is 95 ± 6% for gel-2 (black trace) and 94 ± 6% for the LHCE control (red trace). These values are remarkably similar to those obtained using the same conditions for Li-FeF3 full cells (Figure ; 95 ± 5% and 96 ± 4% for gel-2 and the LHCE control, respectively).