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

Abstract

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/Zrbased conversion coating is mainly composed of . The Ti/Zr treatment cannot only improve the heatsealing 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.

The Preparation, Corrosion Resistance and Formation Mechanism of a New-Type Mo-Based Composite Conversion Coating on 6061 Aluminum Alloy

“…Currently, the mature CCP used in the market is chromate CCP [15][16][17]. However, Cr 6+ in chromate CCP is highly toxic, carcinogenic and bioaccumulative, causing great damage and a serious threat to the environment and human health [18,19]. Many countries have restricted its use [20], and the emergence of new alternative processes has become very important [21,22].…”

Growth process of molybdate conversion coating on the surface of aluminum foil and its adhesive mechanism

“…However, the use of hexavalent chromium is restricted by its high toxicity to humans and environmental contamination. 5 In order to overcome these problems, a number of alternative treatments are proposed using chrome-free solutions such as phosphate (P), 6,7 rare earth salt, 8 permanganate, 9 titanate/zirconate (Ti/Zr), 10,11 and molybdate (Mo). 12,13 However, some problems remain to be solved for these methods.…”

“…The coating obtained by Ti/Zr treatment is generally colorless, or the color depth is too shallow, making it difficult for naked-eye observation of the formation of the coating. 10 The conversion process using organic agents such as silane coupling agent is complicated and requires a drying temperature of over 200 C.…”

Comparison of the Electrochemical Behaviour and Self-sealing of Zirconium Conversion Coatings Applied on Aluminium Alloys of series 1xxx to 7xxx

“…Several studies have shown that zirconium conversion coatings increase the adhesiveness of substrate and the interfacial bond strength between substrate/topcoats. 15,54,[62][63][64][65][66][67] They also reduce the rate of cathodic delamination/filiform corrosion. 42,58,59,64,68 Surface cleaning or pre-treatment before application of ZrCC has an essential effect on the rate of the conversion process and the final properties of coatings.…”