Fig. 2: The preparation and characterization of asymmetric electrolyte.

a Schematic illustration of asymmetric electrolyte design (including one-layer PPFs-SSEs and one-layer PAM hydrogel electrolyte). b SEM image of the PPFs-SSEs. The inset is schematic illustration of crystal structure of the 2D PPF-SSEs. Zn²⁺ ions are highlighted by blue balls. High-resolution XPS spectra of c Zn 2p, d Cu 2p, e N 1 s, f O 2 s and g C 1 s in the PPFs-SSEs. h Optical image of PAM/PPF-SSEs asymmetric electrolyte films. i Ionic conductivity of PPF-SSEs, hydrogel electrolyte and the asymmetric electrolyte. j Electrochemical window of the designed asymmetric and hydrogel electrolyte measured by LSV at 5 mV·s⁻¹. The inset is the enlarged view of Zn²⁺ deposition curves.