Roll-to-roll atomic layer deposition of titania coating on polymeric separators for lithium ion batteries

Atomic layer deposition (ALD) on flexible substrates has rarely been demonstrated using roll-to-roll (R2R) coating configuration. We develop R2R ALD technique to uniformly coat TiO₂ layer on the porous polyethylene (PE) separators for Li-ion batteries (LIBs). The R2R ALD method using titanium isopropoxide and water as the precursors enables a precise control over the growth of TiO₂ nanolayer on PE separators. The TiO₂-coated separators remarkably improve the LIB performance, as compared to the LIBs utilizing pristine polymeric membranes. The TiO₂ deposition also enhances the thermal and dimensional stability, through forming a stabilizing and robust skeleton within the polymeric matrix. Accordingly, the TiO₂ layers play a critical role in boosting the LIB performance, via increasing the ionic conductivity, decreasing high-frequency impedance, and enhancing the electrolyte wettability. Ultimately, the application of ceramic nanocoating on the PE-based porous separators results in improved safety, higher energy density, and excellent cycleability during high-temperature and long-duration cycling of LIBs. Thus, the TiO₂-coated separators can be easily adopted to replace the commercially available separators due to excellent performance and reduced cost of manufacturing. The production rate of the ceramic separators can reach as high as 2.4 m min⁻¹ fulfilling the requirements of the industrial and large-scale production.