Exploring fluoroborate anions for sodium battery technologies

Fluoroborate anions are investigated in electrolytes for sodium battery technologies in this study. The anions are shown to exhibit improved physical and electrochemical properties in comparison to conventional electrolyte materials. Electrolyte safety is improved by synthesising novel ionic liquids with the fluoroborates, involving comprehensive understanding of their physical properties which are sufficient for sodium electrochemistry. The novel ionic liquid [N2(2O2O1)3][B(hfip)4] is further investigated to understand the ion-speciation of the electrolyte which finds the highly concentrated electrolyte to exhibit superior electrochemical behaviour due to labile Na+-ion interactions. This work shows [B(hfip)4]- to be a promising electrolyte anion for sodium batteries.