Preparation and adhesive properties of colored Ti/Zr‐based conversion coating on aluminum foil for lithium battery packaging

In this study, an aluminum (Al) foil used for lithium ion battery packaging film was treated with titanium (Ti)/zirconium (Zr) solution containing hexafluorotitanic acid and hexafluorozirconic acid using tannic acid as a colorant and metavanadate as an accelerator, respectively, and a golden conversion coating was successfully deposited on the surface of Al foil. The morphology and composition of the coating were characterized by scanning electron microscopy, energy dispersive spectroscopy, and X‐ray photoelectron spectroscopy, and the hydrophilicity was assessed by contact angle measurement. The effect of Ti/Zr treatment on the adhesion properties of Al foil was evaluated by T‐peeling test and compared with that of traditional chromate‐phosphate treatment. The results show that tannic acid contributes to the formation of the golden coating, and metavanadate accelerates the formation of the conversion coating. The results also indicate that the Ti/Zr‐based conversion coating is mainly composed of Al 2 O 3 , Al (OH) 3 , AlF 3 , TiO 2 /ZrO 2 , NH 4 VO 3 , and V 2 O 5 . The Ti/Zr treatment cannot only improve the heat‐sealing strength, but also the T‐peeling strength by approximately 12 times compared with that of untreated Al foil. Thus, Ti/Zr treatment has the potential to replace the traditional chromate conversion treatment.