FeF3 half-cells were constructed by pairing FeF3 cathodes (with or without gel-2) with partially delithiated LFP (Li0.66FePO4). Partially delithiated LFP was chosen as a counter electrode in these cells due to its highly stable reference potential (~3.4 V vs. Li/Li + ), which is similar to the open circuit potentials that we observed for the Li-FeF3 full cells (~3.3-3.5 V vs. Li/Li + ).