Electrochemical Performance of BiF3-BaF2 Solid Solution with Three Different Phases on a Fluoride Shuttle Battery System

摘要

Solid solution of bismuth(III) fluoride (BiF3) and barium(II) fluoride (BaF2) with a variety of crystal structures was prepared, and their electrochemical performances were evaluated on a fluoride shuttle battery (FSB) system. BiF3-BaF2 based solid solution (Bi1-xBaxF3-x (x=0) with orthorhombic phase, x=0.2 with hexagonal phase, and x=0.4 with cubic phase) were successfully obtained with the mechanical alloy method. The change from Bi1-xBaxF3-x (x=0) (orthorhombic) to x=0.2 (hexagonal) improved the initial reversible capacity and the capacity retention during cycling. The change from x=0.2 (hexagonal) to 0.4 (cubic) led to further improvement in capacity retention during cycling; however, the initial reversible capacity decreased due to the substitution of excess amount of barium that did not contribute to the redox reaction. For the BiF3-based compound, controlling the crystal structure and substitution of inactive element affected the FSB performance.