The heat-sealing strength of pouch film greatly affects the reliability of the lithium ion secondary battery. In this paper, the researchers investigated and evaluated the properties of the heat-sealing strength of pouch film, such as heat, pressure, time, thickness of the heat-seal, and the polypropylene material. The heat-sealing strength showed a high value at 180℃ for 3 seconds. However, under the conditions of higher temperatures and longer times, deformation and bulging of polypropylene were observed. The heat-sealing strength tended to increase when decreasing heat-seal thickness. The heat-sealing strength varied according to the type of polypropylene. In addition, to avoid defects that may have occurred in the process of manufacturing the lithium ion secondary battery, the heat-sealing strength in the state where the impurities remained was evaluated.

This paper studied the adhesive strength and electrolyte resistance of the pouch film according to the kind of the extruded resin, which is the basis of the numerous variables in extrusion lamination. After preparing a pouch film by using various extruded resins, we measured the adhesive strength and electrolyte resistance between the aluminum foil and the CPP film. The minimal difference was observed between the adhesive strength with the extruded resin. Also, the extruded resin used in the experiment did not satisfy the electrolyte resistance. An electrolyte resistance was obtained by addition of the functional resin to the extruded resin. The addition of functional resins resulted in improved adhesive strength and electrolyte resistance, that were measured to be approximately 1300 gf/15 mm and 800 gf/15 mm, respectively, at 85℃ for 7days.

In this study, we investigated the adhesive strength by molecular weight, mixture ratio, coating thickness, lamination temperature and aging condition of adhesive in manufacture process of Nylon-Aluminum for secondary aluminum pouch. It found that as the molecular weight of adhesive gets lower, the adhesive strength increases. In the mixture ratio, as the content of hardener get higher and as the content of solvent get lower, the adhesive strength increases. Also, as the coating thickness of adhesive get thicker, the adhesive strength increase. In addition, the adhesive strength is higher at 90 degrees of lamination temperature. So, it found that 90 degrees of lamination temperature is appropriate. In the aging condition when aged for 5 days, it found that the reaction and curing of adhesive is sufficient by measuring the adhesive strength.