Fig. 5: Structural evolution of HESSe electrode during Na⁺ storage.

a Contour plot of in situ XRD results and corresponding charge/discharge curves. b Ex situ XPS analysis at pristine, fully sodiated (DC0.1 V) and desodiated (charged to 3.0 V) states. c HAADF-STEM image and the corresponding EDS elemental mappings at DC0.1 V state.