The case for fluoride-ion batteries

Summary

Fluoride-ion batteries (FIBs) have recently emerged as a candidate for the next generation of electrochemical energy storage technologies. On paper, FIBs have the potential to match or even surpass lithium-metal chemistries in terms of energy density, while further eliminating the dependence on strained resources, such as lithium and cobalt. Research into FIBs has accelerated since its inception in 2011. In this perspective, we examine the case for fluoride-ion batteries, considering electrode and electrolytes from the literature and beyond, to outline the potential pathways to a competitive energy storage technology. We present the most promising, feasible conversion-type cathode and anode materials in terms of capacity, electrode potential, volume change, crystal structure, and cost/abundance. The capabilities of current and future fluoride intercalation electrodes are also examined. Using a subset of these materials, we conduct a techno-economic analysis comparing the energy density and cost of conversion and intercalation-type FIBs with state-of-the-art lithium-ion batteries and high-energy-density lithium-metal-based chemistries. This investigation highlights the potential commercial value of conversion-type, liquid-cell FIB, with energy densities as high as 588 Whkg⁻¹ (1,393 WhL⁻¹) and costs as low as 20 US$ kWh⁻¹ at the stack level. This perspective highlights the major obstacles hindering the development of FIBs, drawing relevant lessons from the lithium-ion literature. In order to practically advance FIBs into a viable technology, further research must be focused on safe liquid fluoride electrolytes and solid electrolyte interphase formation; mechanistic study and theoretical modeling of electrode materials; and stable non-active battery components and reference electrodes. We conclude by prescribing several critical research fronts in these areas.