Fig. 4: Understanding of the solution-to-solid chemistry mechanism in the Al | ACC/In cell.

a Ex-situ XRD patterns at different states. A discharging rate is half of a charging one to ensure full reaction on discharge. The weak diffraction peaks marked by asterisks belong to the residual chloroaluminate melt electrolyte. b The XPS spectra of ACC cathode in Al|ACC/In battery before cycling and after full charge. c The SEM image of the ACC cathode after full charge, scale bar: 1 µm. d, e TEM images and FFT pattern of the fully charged product; d scale bar: 2 nm. f–h The HAADF-STEM image and the corresponding element mapping images of the fully charged product; scale bar: 200 nm. i, j In situ time-lapse EIS profiles of the Al|ACC/In cell at different states of charge (SOC) and depths of discharge (DOD) during the initial cycle. k EIS spectra measured at the pristine state, after full charge and after full discharge (inset is the equivalent circuit model for the pristine state and full discharge). HAADF-STEM, high-angle annular dark-field scanning-TEM.