Difficulties faced by domestic 18650 battery lithium ion 2200mah aluminum-plastic film technology

　　Compared with other batteries, soft-pack lithium batteries have the advantages of good safety performance, light weight, large capacity, low internal resistance, and flexible design. They are widely used in consumer electronics, automobiles, special applications, medical, power tools and other industries.

　　The essence of a 18650 battery lithium ion 2200mah is actually just a liquid lithium-ion battery covered with a polymer shell. The aluminum-plastic film in the polymer shell plays an indispensable role in its excellent performance. Then the author will analyze the magical aluminum plastic film for everyone.

　　1. Introduction to aluminum plastic film

　　Aluminum-plastic film is a multi-layer film composed of an outer nylon layer, adhesive, middle aluminum foil, adhesive, and inner heat sealing layer. It is the packaging material for soft-pack lithium batteries. Aluminum plastic film has the following advantages compared with other commonly used plastic films:

　　1) Aluminum-plastic film has extremely high barrier properties: 10,000 times higher than ordinary aluminum-plastic composite films;

　　2) Good cold stamping formability: able to adapt to new battery cell models according to customer product needs.

　　3) Good puncture resistance: Because there are copper and aluminum mesh burrs around the polymer lithium battery core, which causes pitting corrosion and accelerates electrolysis, when vacuuming and gathering, the burrs will pierce the inner membrane and may pierce the inner membrane until Aluminum foil, the hydrofluoric acid in the battery core will directly corrode the aluminum foil and change the composition of the electrolyte. In severe cases, the aluminum foil will be corroded and leaked. At the same time, it will cause a short circuit and cause the battery to be scrapped. Therefore, puncture resistance is particularly important.

　　4) Good electrolyte resistance stability: A variety of organic solvents usually swell, dissolve, and absorb flexible packaging materials. They are good solvents for adhesives and will destroy the bonding effect of the composite layer and change the concentration of components in the electrolyte. , thereby affecting the electrical performance of the battery. The presence of highly corrosive hydrofluoric acid will seriously corrode the aluminum foil, causing the inner film to separate from the aluminum foil, and then corrode and perforate the aluminum foil, thereby destroying the entire package. The good electrolyte resistance stability of the aluminum-plastic film ensures the stability of the entire battery. Safety

　　5) The aluminum-plastic film is resistant to high temperatures and has strong insulation: the thickness of the metal electrode sheet is about 100u. When heat-sealing at 170°C and a pressure of about 3kg/cm2, if there is no high-temperature-resistant insulating layer in the inner film, the metal electrode is often It will overwhelm the packaging aluminum foil, causing a short circuit, causing the battery to be scrapped and the yield to be reduced. Therefore, high temperature resistance and insulation resistance are essential attributes of the casing.

　　2. Structure and classification of aluminum plastic film

　　The main component of the aluminum plastic film is composed of three layers of ON/ALCPP. The surface ON layer (nylon layer) is a decorative ON layer, which also protects the AL layer from scratches; the middle layer is AL that forms shapes and prevents moisture intrusion. layer; the inner CPP (polypropylene) layer is an electrolyte-resistant layer.

　　According to different preparation processes, aluminum-plastic films can be divided into the following two categories. The following are typical structural diagrams of Japan Printing (DNP) and Showa Denko aluminum-plastic films:

　　1490838548942219.png

　　The dry method is widely used. 95% of Showa ALF's output is dry method, which is mainly used in high-energy and heavy batteries such as mobile phone batteries, MP3, and MP4. In addition, it is also widely used in electric vehicles, model aircraft, and other high-rate, high-capacity power batteries; the thermal method can only be applied to batteries that do not have high capacity requirements.

　　3. Preparation process of aluminum plastic film

　　Generally speaking, the preparation methods of aluminum-plastic films are divided into two categories: dry method and heat sealing:

　　Dry method: AL and CPP are bonded with an adhesive and then directly pressed together. The advantages lie in reaffirming the molding performance, short-circuit prevention performance, appearance (less impurities, pinholes, and fish eyes), and cutting performance. In addition, it has good electrolyte resistance and water barrier properties.

　　Heat sealing: MPP is used to connect AL and CPP, and then thermally synthesized under slowly increasing temperature and pressure conditions. The production process is long. And due to long-term high-temperature baking, ALF becomes embrittled, resulting in deterioration of punching performance. The advantage is only in electrolyte resistance and water resistance, but its deep forming performance, short circuit prevention performance, appearance, and cutting performance are not ideal.

　　4. Difficulties faced by domestic aluminum-plastic film manufacturers

　　At present, the performance of my country's aluminum-plastic film products, only a few technical indicators of a few companies can reach the level of Japanese companies. The main problems are electrolyte resistance and penetration depth. The penetration depth of domestic aluminum-plastic film is about 5mm. Foreign products are at 8mm or even 15mm, and there is still a certain gap between them and foreign products. Especially the reaction conditions and precision control. In this high-precision material manufacturing process, the difference is often a thousand miles, and the difficulty of process control is reflected in the millimeter. At present, domestic aluminum-plastic film manufacturers are facing the following five major dilemmas:

　　1) The surface treatment process of aluminum foil is backward and pollutes a lot: due to the use of water to wash out oil and "chromic anhydride" passivation treatment, the pollution is big. At the same time, due to the surface tension of water, the oil in the micropores of the aluminum foil cannot be cleaned, causing defects in subsequent processes;

　　2) The water treatment process of aluminum foil will produce "hydrogen embrittlement", so the domestic aluminum-plastic film has poor tearing resistance;

　　3) The surface of the aluminum foil is coated with a UV layer, and the stiffness of the aluminum foil is not enough. It is easy to wrinkle during dry lamination. Wide-width products cannot be produced and the yield is poor;

　　4) For CPP, laminating machines are mainly used in China for laminating. When combined with the surface of aluminum foil with high thermal conductivity, it is easy to curl and produce lamellar crystals;

　　5) Due to domestic adhesive formulation technology, products are prone to delamination and peeling problems.

　　Domestic lithium battery manufacturers are facing huge cost pressure and are urgently required to reduce the cost of lithium battery raw materials. Therefore, the need for import substitution and localization of aluminum-plastic films has become increasingly prominent.

Read recommendations:

521133 160MAH 3.7V

Why is lithium iron phosphate battery more expensive than ternary lithium batteries.Column rechargea

Want to know where is the advantage of ternary lithium batteries?solar energy storage lithium ion ba

551235 battery wholesaler

AG11 battery