Figure 8.

(a) Typical voltage vs. SOC plots of Na-NiCl₂ and Na-FeCl₂ cells. (b) Crystal structures of three key phases, (b-1) NaCl, (b-2) Na₆FeCl₈, and (b-3) FeCl₂, involved in the charging process of a Na-FeCl₂ battery. The red spheres represent Cl⁻ ions, while yellow and blue octahedra are, respectively, six-coordinated NaCl₆ and FeCl₆. The (111) plane is indicated by light blue for NaCl and Na₆FeCl₈. (c) Rate performance of a Na-FeCl₂ battery operated at 190 °C. (d) The evolution of normalized capacity (SOC, %) as a function of C-rate for Na-FeCl₂ batteries. The data of Na-NiCl₂ batteries (red points and line) were included as references. (e) Stable long-term cycling performance in terms of specific capacity of Na-FeCl₂ batteries with 10 wt.% Ni as cathode additive (adapted with the permission from Wiley).