Developing intercalation based anode materials for fluoride-ion batteries: topochemical reduction of Sr₂TiO₃F₂via a hydride based defluorination process

Abstract

Sr2TiO3F2−x, a potential anode material for fluoride ion batteries, is prepared in the charged state via selective low-temperature defluorination.

Layered electrides as fluoride intercalation anodes

“…This is generally true for similar electrodes such as MgFeSb4O8F (39 mAh/g) or CoFeSb4O8F (37 mAh/g), 30 although it can be mitigated by using cations lighter than La or Sb, such as Sr (1.26 Å) in Sr2TiO3F2 (197 mAh/g), which has been proposed as a FiB anode but not yet tested. 31 We conclude that to keep the electrode light, yet retain large interstitial sites, it should ideally have only one type of cation. Alkali and alkaline earth metals are light, large, inexpensive, and have low charge, satisfying all the constraints except redox activity, so we can expect good results if these metals can be stabilized in oxidation states besides +1 and +2, respectively.…”

Reversible Electrochemical Intercalation and Deintercalation of Fluoride Ions into Host Lattices with Schafarzikite‐Type Structure

“…The volume changes of the active cathode material structures also calculated to be approximately 1.8 and 1.7 % for Co 0.5 Fe 0.5 Sb 2 O 4 and Mg 0.5 Fe 0.5 Sb 2 O 4 , respectively (from 433.8(2) to 426.2(4) Å 3 on fluorination for Co 0.5 Fe 0.5 Sb 2 O 4 , and from 433.0(2) to 425.7(2) Å 3 on fluorination for Mg 0.5 Fe 0.5 Sb 2 O 4 . We would like to point out that those changes are very low as compared to Ruddlesden–Popper‐type compounds, which are on the order of 10–20 % …”

“…[8] The volumec hanges of the active cathode materials tructures also calculated to be approximately 1. 8 [5,[8][9] Once fully charged, the discharge profiles of the materials were investigated, as shown in Figure4a. The discharge capacities were found to be very low,o nt he ordero f 6.0 mAh g À1 (corresponding to ca.…”

“…Fluorine insertion into metal oxides has become an interesting topic over the past years, owing to the potential for modifying the electronic, magnetic, and superconducting behavior of host lattices through structural and compositional changes. Furthermore, such oxide materials are considered reversible electrode materials for fluoride‐ion batteries (which were previously based on conversion‐type compounds), for which currently only compounds with Ruddlesden–Popper‐type structure are known to show principle structural reversibility …”

“…Furthermore, such oxide materials are considered reversible electrode materials for fluoride-ion batteries (whichw ere previously based on conversion-type compounds), [4] for which currently only compounds with Ruddlesden-Popper-type structure are known to show principle structural reversibility. [5] Chemical fluorination of the oxides has predominantly been performed via chemical reactions, for example, by heating samples under flowing F 2 gas [6] or with milder fluorination agents such as PVDF. [7] The use of oxidative agents (F 2 ,C uF 2 , AgF 2 )i sc hallenging, and can often lead to the decomposition of the target compounds.…”