Evidence of a reversible redox reaction in a liquid-electrolyte-type fluoride-ion battery

Abstract

Fluoride-ion batteries (FIBs) is a promising alternative to conventional lithium-ion batteries, but a reversible redox reaction has not yet been confirmed. Structural and compositional analyses revealed the reversible redox reaction, aiding further development of FIBs.

Redox Reaction Mechanism of Graphite Fluoride (CF)n in Fluoride-Ion Batteries

“…However, the reversibility of the redox reaction in the Pb plate was low (Figure S6). Therefore, the low reversibility of the (CF) n |TEAF/PC|Pb cell can be attributed not only to the (CF) n positive electrode but also to the low reversibility of the Pb plate negative electrode …”

“…Although research on all-solid-state FIBs is more advanced than that on liquid-electrolyte-type FIBs, the use of liquid-based FIBs allows a more detailed analysis of the electrode. The electrolyte was 0.1 M tetraethylammonium fluoride (TEAF) dissolved in propylene carbonate (PC) as a liquid electrolyte (TEAF/PC), which is the electrolyte used in our previous study . Pb metal, which has been proven to be redox-reactive in this electrolyte, was used as the negative electrode.…”

Advancing Fluoride-Ion Batteries with a Pb-PbF2 Counter Electrode and a Diluted Liquid Electrolyte

“…However, their cell exhibited low discharge capacity (110 mAh g −1 on first discharge) and poor cycling (∼0 mAh g −1 on fifth cycle), partly because of the poor performance of the Pb counter electrode. 7 Other studies with two-electrode cells have also resulted in poor performance. To design a stable counter electrode, Nowroozi et al proposed the use of intercalation compounds, particularly La 2 CoO 4 , because of the lower volume changes during cycling (compared to those of conversion-type electrodes), which might provide a more reliable performance.…”

“…The advancement of fluoride-ion batteries, however, has been hindered by several obstacles. One of these is the lack of a realistic and reproducible testing setup . Flooded cells (also known as beaker cells) are commonly used to test the electrochemical properties of liquid electrolyte FIBs.…”

“…Flooded cells (also known as beaker cells) are commonly used to test the electrochemical properties of liquid electrolyte FIBs. However, they impede the realistic assessment of performance given the large excess of electrolyte, the absence of a separator and, in many cases, the use of Pt as the counter electrode, which inevitably results in electrolyte decomposition during cycling. − …”