Binder-Free Nanoparticulate Coating of a Polyethylene Separator via a Reactive Atmospheric Pressure Plasma for Lithium-Ion Batteries with Improved Performances

A reactive atmospheric pressure plasma containing Ar/O-2/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 approximate to 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.