Modification of SnF2 cathode material of a fluoride-ion electrochemical cell with carbon additives

Abstract

This article presents studies of carbon additives (graphite, thermally expended graphite (TEG), expandable graphite (EG), graphene, single-walled carbon nanotubes (SWCNT), nanocomposite SnF2@SWCNT) in the cathode material (SnF2) of solid-state fluoride-ion galvanic cells. The cells are made in the form of multilayer pellets: metallic cerium anode, tysonite solid solution of barium fluoride in the lanthanium fluoride La1−xBaxF3−x (x ≈ 0.05) electrolyte, SnF2 cathode with carbon additive. The pellets are investigated by scanning electron microscopy, cyclic voltammetry, impedance spectroscopy. Carbon additives are characterized by Raman spectroscopy. The original galvanic cell with SnF2 cathode without additives has open-circuit voltage (OCV) 1.69 V (at room temperature) and ∼1.46 V (at 180 °C). The galvanic cell with EG additive (mechanical mixture) has OCV 2.45 V at room temperature. The introduction of a carbon additive into the tin fluoride melt, followed by mechanical grinding to create a cathode material, reduces the current density. The use of SnF2@SWCNT nanocomposite increases the current density (1.295 A/m2) by more than 2.5 times compared to pure nanotubes. The current density of FIB with SnF2@SWCNT exceeds the values obtained with other carbon additives in the cathode material.