Fig. 2: Interfacial electric double layer and solvation structures of AC, CMS-800, and CMS-1300 negative electrodes.

a Differential capacitance values of three negative electrodes across the working potential range of the electric double layer. The vertical line indicates the potential of zero charge (PZC). The vertical axis represents the capacitance per unit surface area of the material. AC negative electrode uses a smaller voltage window than CMS-800 and CMS-1300 negative electrodes because the electrolyte decomposes at high potentials. b The CV curve (dashed line) and the mass change-potential profile during discharge (solid line) for the three negative electrodes. The vertical dashed line marks the PZC. The left and right vertical axes represent the mass change and the current change per unit surface area of the material, respectively. c The mass change-charge profile corresponding to the selected section in (b). d Raman spectra in the regions of 710–780 cm⁻¹, e C=O peaks in FTIR spectra, and f ¹⁹F ssNMR spectra of the electrolytes in the three negative electrodes after an initial discharge to 1.5 V. The fitted data in d and e are depicted with short dashed lines. Sodium atoms are shown as gray spheres. Fluorine atoms and phosphorus atoms are shown as blue and yellow spheres, respectively. Source data are provided as a Source Data file.