Improved electrochemical performances in a bismuth fluoride electrode prepared using a high energy ball mill with carbon for fluoride shuttle batteries

Abstract

Bismuth fluoride (BiF₃) is a promising positive electrode material for fluoride shuttle batteries (FSBs) owing to its high theoretical specific capacity (302 mA h g⁻¹). However, it exhibits low practical capacity. The methods for preparing the electrode are known to have significant effects on battery performance. The mixture between BiF₃ and carbon, BiF₃/C, prepared by high energy ball milling method has been already approved in lithium ion batteries. With this method, a significant improvement over the discharge and charge capacities of the BiF₃/C electrode has been achieved. In this work, for the first time, BiF₃/C electrode has been used for FSB. Using BiF₃/C electrode significantly increased the discharge and charge capacities. To confirm the progress of the discharge and charge reactions of BiF3/C electrode, the crystal structure of active materials and oxidation state of Bi for the BiF₃/C electrode during discharging and charging has been investigated by X-ray diffraction and X-ray absorption fine structure. The results reveal that, with higher capacity values, discharge and charge reactions related to BiF₃/C have been realized.