Research On Pilot-scale Production Process Of Aluminum Laminated Film For Lithium Ion Battery

With the increasing requirements of energy density for new energy vehicles,the development of high energy density batteries is a hot spot in the future.The energy density of the soft pack battery with aluminum laminated film as outer packaging material is 5～15%higher than that of the cylindrical battery and square battery with steel shell and aluminum shell,which provides a solution for the high energy of lithium battery.Besides this,the soft pack battery also has the advantages of high safety and flexible design.Aluminum laminated film is one of the core materials for soft pack battery,which is made of nylon,aluminum foil and PP by adhesive.Although its structure is simple,but the raw materials rely on imports,backward production equipment,lack of research on the aluminum foil processing technology and composite glue formula,has not yet achieved full localization.The aluminum foil needs to be passivated with chromium containing solution,which causes serious pollution.The stability of the glue and the electrolyte resistance are not good.The product is easy to be peeled off by wet heat test and electrolyte immersion test,which affects its practical application.In this paper,the aluminum foil was anodized,the aluminum laminated film semifinished product was anodized,and then coated with nylon and PP,the peel strength was tested after curing.The peel strength of the treated aluminum foil and nylon reaches 8.2N/15mm,which reduces the problems of heat sealing and wet heat delamination of nylon and aluminum foil.The peel strength of aluminum foil and PP can reach 20.3N/15mm,and the peel strength can still maintain 13.6N/15mm after immersion in electrolyte,which is higher than the industry standard of 8.0N/15mm.After anodizing,honeycomb structure is formed on the surface of aluminum foil,which can mesh with the glue mechanically and increase the peel strength.The main components of the oxide film are alumina(Al2O3)and aluminum fluoride(AlF3),which have strong corrosion resistance,so the aluminum laminated film is endowed with excellent electrolyte resistance.The anodized aluminum foil was sprayed with gold,and a series of color aluminum alloys were prepared.In addition,the pilot scale-up production of the aluminum laminated film pilot parameters accumulated in the laboratory for many years is carried out.During the pilot test,the basic performance of the material is tested,the appropriate substrate is selected,and the alkaline washing and coating process parameters are optimized.Compared with the laboratory process,the peel strength of aluminum foil and PP is increased by 5.5N/15mm.The peel strength of the sample aluminum foil and PP after immersion in the electrolyte increased by 3.1N/15mm.In order to solve the problem that aluminum laminated film is prone to cracking during deep drawing,the friction coefficient of nylon and PP is tested,stamping dies with different roughness are selected,and the surface of the material is coated with a slip agent to reduce the friction coefficient,which improves the quality of the sample stamping molding rate.Test the heat-sealing strength of the PP layer of the aluminum laminated film under different heat-sealing temperatures and times to determine the appropriate heat-sealing parameters.The optimized process and experimental parameters of the pilot experiment provide suggestions for the transformation of aluminum laminated film project results and the realization of large-scale production in the factory.