1. (a) XRD pattern, (b)SEM image, (c)AFM image, and (d) cross-sectional height profile of boehmite nanosheets

2. Physical properties of PE, PE-AlOOH_NP and PE-AlOOH_NS

3. (a)Nyquist plots of SS/SS cells assembled with different separators; (b) Chronoamperometry profile of Li/PE-AlOOH_NS/Li cell with inset showing EIS plots before and after polarization; (c) LSV curves of SS/Li cells assembled with different separators; (d) Rate capabilities, (e) EIS spectra and (f) cycle performances of LFP/Li cells with different separators

4. Voltage profiles of Li/Li symmetric cells assembled with (a) PE, (b) PE-AlOOH_NP and (c) PE-AlOOH_NS, and (d) schematic illustration of suppressing lithium dendrite formation

S1. Particle size distribution of boehmite nanosheets

S2. DSC curves of different separators

S3. Chronoamperometry profile of Li/PE/Li cell with inset showing the EIS plots before and after polarization

S4. Chronoamperometry profile of Li/PE-AlOOH_NP/Li cell with inset showing the EIS plots before and after polarization

Table 1. Physical parameters of different separators