Synthesis of Fast Fluoride-Ion-Conductive Fluorite-Type Ba1- xSb xF2+ x (0.1 ≤ x ≤ 0.4): A Potential Solid Electrolyte for Fluoride-Ion Batteries

Irshad Mohammad; Johann Chable; Raiker Witter; Maximilian Fichtner; M Anji Reddy

doi:10.1021/acsami.8b04108

Synthesis of Fast Fluoride-Ion-Conductive Fluorite-Type Ba_{1- x}Sb _xF_{2+ x} (0.1 ≤ x ≤ 0.4): A Potential Solid Electrolyte for Fluoride-Ion Batteries

ACS Appl Mater Interfaces. 2018 May 23;10(20):17249-17256. doi: 10.1021/acsami.8b04108. Epub 2018 May 9.

Authors

Irshad Mohammad^{1

2}, Johann Chable², Raiker Witter^{1

3}, Maximilian Fichtner^{2

3}, M Anji Reddy²

Affiliations

¹ Technomedicum , Tallinn University of Technology , Ehitajate tee 5 , 19086 Tallinn , Estonia.
² Helmholtz Institute Ulm (HIU) for Electrochemical Energy Storage, Helmholtz Str. 11 , 89081 Ulm , Germany.
³ Institute of Nanotechnology (INT) , Karlsruhe Institute of Technology (KIT) , Hermann-von-Helmholtz-Platz 1 , 76344 Eggenstein-Leopoldshafen , Germany.

PMID: 29741368
DOI: 10.1021/acsami.8b04108

Abstract

Toward the development of high-performance solid electrolytes for fluoride-ion batteries, fluorite-type nanostructured solid solutions of Ba_{1- x}Sb _xF_{2+ x} ( x ≤ 0.4) were synthesized by high-energy ball-milling method. Substitution of divalent Ba²⁺ by trivalent Sb³⁺ leads to an increase in interstitial fluoride-ion concentration, which enhances the ionic conductivity of the Ba_{1- x}Sb _xF_{2+ x} (0.1 ≤ x ≤ 0.4) system. Total ionic conductivities of 4.4 × 10^-4 and 3.9 × 10^-4 S cm^-1 were obtained for Ba_0.7Sb_0.3F_2.3 and Ba_0.6Sb_0.4F_2.4 compositions at 160 °C, respectively. In comparison to isostructural Ba_0.3La_0.7F_2.3, the ionic conductivity of Ba_0.7Sb_0.3F_2.3 is significantly higher, which is attributed to the presence of an electron lone pair on Sb³⁺. Introduction of such lone pairs seems to increase fluoride-ion mobility in solid solutions. In addition, Ba_0.7Sb_0.3F_2.3 was tested as a cathode material against Ce and Zn anode using La_0.9Ba_0.1F_2.9 as the electrolyte. Ba_0.3Sb_0.7F_2.3/La_0.9Ba_0.1F_2.9/Ce cell showed high discharge and charge capacities of 301 and 170 mA h g^-1, respectively, in the first cycle at 150 °C.

Keywords: fluoride-ion batteries; fluoride-ion conductors; fluorite-type fluorides; ionic conductivity; solid electrolyte; solid-state batteries.