S.J. Percival, M. Stalcup, A.M. Maraschky, L.J. Small, A.S. Peretti, E.D. Spoerke
Sandia National Laboratories,
United States
Keywords: Energy Storage, Electrochemistry, Battery, Catholyte, Molten Salt, Sodium, Aluminum, Iron, Metal Halides.
Summary:
A novel Al-Fe based molten salt catholyte is developed that when paired with a molten sodium anode has a high operating potential that rivals much more expensive, and less safe, Li ion batteries. This molten salt catholyte consisting of AlCl3-NaCl-FeCl3/FeCl2, was at first predicted to have an operating cell voltage of 3.45 V (vs Na/Na+) but upon testing it demonstrated a much higher voltage of 3.92 V (vs Na/Na+). The higher voltage is attributed to the abundance of free chloride in the salt and the operational battery reducing FeCl3 when discharging and oxidizing Cl- when charging. The catholyte is shown to have stable cycling at low and intermediate rates with excellent energy efficiencies. The battery is also shown to be able to have a lower potential SOC (~3.4 V vs Na/Na+) where the catholyte could be cycled between the intended FeCl3/FeCl2 redox species in the molten salt. The battery chemistry can be tailored to also cycle between the FeCl3/FeCl2 redox pair if desired, but at a lower operating potential. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. SAND2024-03868A