1. (a) Crystal structure of UiO-66, and SEM images of (b) nano-sized UiO-66 and (c) UiO-66/PEO composite polymer electrolyte

2. (a) XRD patterns of simulated UiO-66, synthesized nano-sized UiO-66, PEO, and CPE-10%; (b) Arrhenius plots for the ionic conductivities of PEO electrolytes with different contents of UiO-66; (c) Nyqiust plots within frequency of 1 Hz-1 MHz for the CPE-10% at the temperature from 25 to 80 ℃; (d) LSV curves of SPE and CPE in SS/electrolyte/Li cells at 60 ℃; (e) DC polarization profile of symmetric Li/SPE /Li cell at an applied voltage of 10 mV at 60 ℃; (f) DC polarization profile of symmetric Li/CPE-10%/Li cell at an applied voltage of 10 mV at 60 ℃. Insets in (e,f): AC impedance spectra of the corresponding symmetric cells before and after DC polarization

3. (a) Galvanostatic cycles with a constant current density of 0.15 mA∙cm^-2 for symmetric Li/CPE-10%/Li and Li/SPE/Li cells at 60 ℃, (b) magnification of galvanostatic cycles of Li/CPE-10%/Li and Li/SPE/Li cells at 1-10 cycle, and (c) magnification of galvanostatic cycles of Li/CPE-10%/Li cell at 895-900 cycle