Ti/Cr(III) conversion coating on aluminium foil for lithium-ion battery package

Trivalent chromium (Cr(III)) was added into a titanium (Ti)-based solution in this study to prepare Ti/Cr(III) conversion coatings on the aluminium (Al) foil for lithium-ion battery package. Their surface morphology and chemical composition were characterized by field-emission scanning electron microscope (FE-SEM), energy-dispersive spectroscopy and X-ray photoelectron spectroscopy (XPS). The corrosion resistance and the adhesive strength between Al foil and hot melt adhesive (modified polypropylene film) were determined. The results reveal that the Ti/Cr(III) conversion coating is mainly composed of Al2O3, TiO2, Cr(OH)3 and Cr2O3, and possesses the best anticorrosive performance with a corrosion current density of 1.05 µA cm−2, which is one order of magnitude lower than pure Al foil. The adhesive strength between Ti/Cr(III)-treated Al foil and the adhesive is 14.3 N/15 mm with an increase of 250% compared with the pure Al foil, which meets the industry standard (12 N/15 mm).