The packaging material used in pouch lithium batteries is an aluminum-plastic composite film, or aluminum-plastic film for short, which is mainly used for the outer packaging of pouch lithium-ion battery cells. Pouch lithium batteries packaged with aluminum-plastic film are mainly used in the 3C field, and in recent years have gradually penetrated into the new energy vehicle industry, providing safe and stable power output for various models of vehicles.
The design and manufacturing technology of aluminum-plastic film is highly demanding. Currently, 90% of the domestic market is monopolized by Japanese and South Korean companies such as DNP/Showa Denko and Kurimura. Domestic companies, such as Xinlun Technology and Foshan Plastics Technology, are also accelerating the development and production of aluminum-plastic film, but there is still a certain gap compared with Japanese and South Korean companies. Aluminum-plastic film comes in different thicknesses, and its structure is mainly composed of three materials: a CPP layer, an Al layer, and a nylon layer from the inside out.
There are two main manufacturing methods for aluminum-plastic composite films: the thermal method and the dry method. The thermal method involves bonding an aluminum layer and a CPP layer with MPP (methyl methacrylate) and then hot-pressing them together at a specific temperature. At high temperatures, the van der Waals forces in the MPP are disrupted, leading to aging and a sharp decline in its short-circuit resistance. Simultaneously, the destruction of its intermolecular structure reduces its toughness, making it prone to cracking during the molding process.
The dry process involves directly laminating the PP and aluminum layers with an adhesive. Using an insulating adhesive, it eliminates the need for high-temperature treatment, thus offering better short-circuit protection than the thermal process. Furthermore, the adhesive itself has better ductility than the PP layer, and the absence of high-temperature treatment does not affect the molding process.
Aluminum-plastic film, as a core material for secondary batteries, is known for its high technological barriers and high returns. The market is growing rapidly at a compound annual growth rate (CAGR) of 42%.
It is understood that due to the high difficulty of aluminum-plastic film production process, most domestic aluminum-plastic films are not up to standard in terms of resistance to electrolyte corrosion and deep drawing performance. Therefore, the global and domestic aluminum-plastic film market is currently mainly monopolized by a few Japanese companies such as DNP Printing and Showa Denko.
However, with the advancement of domestic battery technology, domestically produced aluminum-plastic film has also made significant progress. For example, Mingguan New Materials, drawing on its extensive experience in developing adhesives for solar cell backsheet films, successfully developed lithium battery aluminum-plastic film using imported adhesives. Building upon this success, they conducted extensive material screening and formulation optimization experiments, successfully developing a product that can replace imported adhesives. The successful development and use of this adhesive not only broke the technological monopoly of foreign counterparts but also represented a major step forward in the complete domestic production of aluminum-plastic film.
Companies such as Xinlun Technology, LiDun Materials/Grepp have also achieved good results in the aluminum-plastic film market.
