Enhanced Wettability of a PTFE Porous Membrane for a High‐Temperature Stable Lithium‐Ion Battery Separator

A hydrophobic poly(tetrafluoroethylene) (PTFE) porous membrane was modified into a hydrophilic lithium‐ion battery (LIB) separator with a higher affinity to the electrolyte via the hybrid consisting of a cationic fluorocarbon surfactant (FCS), polyethylenimine (PEI), and tetraethyl orthosilicate (TEOS), which can be in‐situ biomineralized into SiO2 nanoparticles. The obtained PTFE/FCS‐PEI‐SiO2 separator showed a dynamic electrolyte contact angle, which decreased from 50.3° to 0° within 4 s, along with 215 % of electrolyte uptake. The ionic conductivity and the interfacial resistance were 9.12 mS cm−1 and 228.8 Ω, respectively. In addition, the cell equipped with the separator showed a capacity of 163.7 mAh g−1 at a current density of 0.2 C. Notably, the cell with the separator displayed good high‐temperature stability. The hydrophobic PTFE porous membrane was modified with fluorocarbon surfactant (FCS), polyethylenimine (PEI), and tetraethyl orthosilicate into a hydrophilic lithium‐ion battery separator. The separator had a negatively charged, superhydrophilic surface and high affinity to the electrolyte. The cell with the PTFE/FCS‐PEI‐SiO2 separator exhibited good high‐temperature endurance and stability.