Construction of solid-liquid fluorine transport channel to enable highly reversible conversion cathodes.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 34730994.
- Also identified by DOI 10.1126/sciadv.abj1491 and PMC identifier 8565847.
- Licence recorded as CC BY-NC.
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Abstract
Conversion-type iron fluoride is a promising alternative cathode to intercalation oxides because of its higher energy density. However, its intrinsic solid-solid conversion is sluggish during repeated splitting and rebonding of metal-fluorine moieties. Here, we propose a solid-liquid conversion mechanism to activate the fluorine transport kinetics of iron oxyfluorides enabled by fluoride anion receptor of tris(pentafluorophenyl)borane (TPFPB). TPFPB promotes the dissociation of inert lithium fluoride and provides a facile fluorine transport channel at multiphase interfaces via the formation of solvated F<sup>−</sup> intermediate therein. The construction of solid-liquid channel with fluorinated cathode electrolyte interface is the key for the achievement of FeO<sub>0.3</sub>F<sub>1.7</sub> and FeO<sub>0.7</sub>F<sub>1.3</sub> in terms of sustaining conversion reaction (with an energy efficiency approaching 80%) and high-rate performance (with reversible capacity of 320 mAh/g at 2 A/g). The cathode energy densities can reach 1100 Wh/kg for FeO<sub>0.3</sub>F<sub>1.7</sub> and 700 Wh/kg for FeO<sub>0.7</sub>F<sub>1.3</sub> under the power densities of 220 and 4300 W/kg, respectively.