Effect of anion acceptor added to the electrolyte on the electrochemical performance of bismuth(III) fluoride in a fluoride shuttle battery

[Display omitted] •The reversible capacity of BiF3 electrode is affected by the anion acceptor type in the electrolyte.•The fluoride ion interacts with anion acceptor in the electrolyte.•The chemical state of fluoride ion affects the battery performance of BiF3 electrode. An electrolyte for fluoride shuttle battery was composed of bis[2-(2-methoxyethoxy)ethyl]ether, a cesium fluoride, and an anion acceptor (AA; triphenylborane, fluorobis(2,4,6-trimethylphenyl)borane, or triphenylboroxine). The battery performance of bismuth(III) fluoride in the electrolytes with fluorobis(2,4,6-trimethylphenyl)borane and triphenylboroxine was much higher than that in the electrolyte with triphenylborane. To evaluate the AA type on battery performance, the chemical state of each ion in the electrolyte was evaluated by nuclear magnetic resonance. The chemical shift of fluoride ion interacted with fluorobis(2,4,6-trimethylphenyl)borane and triphenylboroxine was different from that interacted with triphenylborane, indicating that the chemical state of fluoride ion in the electrolyte affects battery performance.