Talcum-doped composite separator with superior wettability and heatproof properties for high-rate lithium metal batteries

摘要

Separator is supposed to own outstanding thermal stability,superior wettability and electrolyte uptake,which is essential for developing high-rate and safe lithium metal batteries(LMBs).However,commercial polyolefin separators possess poor wettability and limited electrolyte uptake.For addressing this issue,we put forward a composite separator to implement above functions by doping layered-silicate(talcum)into polyvinylidene fluoride(PVDF).With significant improvement of electrolyte absorption benefiting from the strong adsorption energy values(-1.64-1.70 eV)between talcum and the electrolyte in lithium metal batteries,PVDF/Talcum(PVDF/TM)composite separator owns a small contact angle and superior electrolyte uptake.PVDF/TM composite separator with 10 wt%talcum(T-10)owns a tiny contact angle of 8°,while those of polypropylene(PP)and PVDF are 48°and 20°with commercial electrolyte.Moreover,the addition of thermotolerant talcum endows the T-10 composite separator with great thermostability,whose thermal shrinkage is only 5.39%at 150°C for 0.5 h.The cell with LiFeO4cathode and the T-10 composite separator reaches 91.7 m Ah/g in discharge capacity at 4.8 m A/cm^(2)(10 C),far superior to that with pure PVDF separator(56.3 m Ah/g)and PP(51.4 m Ah/g).