A reactive atmospheric pressure plasma containing Ar/O2/hexamethyldisiloxane is applied to coat polyethylene (PE) separators for lithium‐ion batteries. The PE separator moves through the plasma region roll‐to‐roll, and its top and internal fiber surface is coated with a thin SiOxCyHz film composed of nanoparticulates with an average size of ≈100 nm. The nanoparticulate film has relatively high heat resistance, which provides a PE separator capable of structural support with improved thermal stability. Meanwhile, the polar functional groups on the PE surface improve its crucial properties such as wettability, electrolyte uptake, and ionic conductivity. A mere 3 min of coating endows the lithium‐ion battery with a lower interface resistance and improved C‐rate and cycling performances. Most importantly, the binder‐free coating method provides a new, eco‐efficient way to improve the performances of polyolefin separators for lithium‐ion batteries.

For the ever-increasing demand for highly safe lithium-ion batteries (LIBs), the common sol-gel process provides heat-resistance to separators with an inorganic coating, where the adhesion to the separator is the key to safety and stability. In this paper, we present a SiO2.01C0.23Hx-coated polyethylene (PE) separator through a roll-to-roll atmospheric plasma-enhanced chemical vapor deposition (R2R-APECVD) of hexamethyldisiloxane (HMDSO)/Ar/O2. The adhesion strength of SiO2.01C0.23Hx-coated PE was tested by peel-off test and found to be higher than that of the commercial Al2O3-coated separator (0.28 N/mm vs. 0.06 N/mm). Furthermore, the SiO2.01C0.23Hx-coated PE separator showed better electrochemical performance in C-rate and long term cycle tests. FTIR, SEM, and XPS analysis indicate that the increased adhesion and electrochemical performance are attributed to the inner hybrid SiO2.01C0.23Hx coating with organic and inorganic components.