What are the five dilemmas faced by domestic aluminum plastic film technology?

Compared with other batteries, soft-pack lithium batteries are widely used in consumer electronics, automotive, military, medical, electric tools and other industries due to their advantages of good safety performance, light weight, large capacity, small internal resistance and flexible design.

The essence of soft-pack lithium battery is just a layer of polymer shell on the liquid lithium ion battery, and its performance is so excellent, which is due to the aluminum plastic film in the polymer shell. Then the author will analyze the magic aluminum plastic film for you.

First, introduction of aluminum plastic film consumer electronics

Aluminum plastic film is composed of the outer layer of nylon, adhesives, middle layer of aluminum foil, adhesives, the inner layer of hot sealing layer of multi-layer film, is a soft package of lithium battery packaging materials. Compared with other common plastic films, aluminum plastic film has the following advantages:

1) Aluminum plastic film has a very high barrier: the barrier of ordinary aluminum plastic composite film is 10,000 times higher;

2) Good cold stamping formability: according to the customer's product requirements, fit the new cell model.

3) Good durability thorn: due to the polymer lithium battery core with copper, aluminum net burr cause pitting corrosion, accelerate electrochemical, vacuum scatters, the burr will dart lining, may puncture the lining to the aluminum foil, batteries in hydrofluoric acid corrosion will direct the aluminum foil to learn, to change the electrolyte composition, serious when wear the aluminum foil corrosion and leakage, and can cause short circuit, leading to dead batteries, so the puncture resistance is especially important.

4) Good electrolyte stability: a variety of organic solvents usually swell, dissolve and absorb soft packaging materials, they are good solvents of adhesive, will destroy the bonding effect of composite layer, change the concentration of components in the electrolyte, and then affect the electrical performance of the battery. The presence of highly corrosive hydrofluoric acid will seriously corrode the aluminum foil, so that the inner membrane and aluminum foil are separated, and then the aluminum foil corrosion perforation, so as to destroy the whole package, and aluminum plastic film good electrolyte stability, to ensure the safety of the whole battery.

5) Aluminum membrane resistance to high temperature, strong insulation: metal electrode slice thickness of about 100 u, about 3 kg/cm2 at 170 ℃ and under the pressure of the heat sealing, lining if there is no high temperature resistant insulating layer exists, metal electrodes is often overwhelming packaging aluminum foil, cause a short-circuit and make a battery scrap, yield reduction, therefore, high temperature resistant, resistant insulation is the essential attribute of the shell.

Second, the structure and classification of aluminum-plastic film

The main composition of the aluminum plastic film is composed of ON/ALCPP three-layer material, the surface layer ON layer (nylon) for decorative ON the layer, also don't scrape the role of protecting AL layer; Intermediate for shape and AL layer to prevent moisture intrusion; The inner CPP (polypropylene) for resistance to electrolyte layer.

According to the different preparation process, aluminum plastic film can be divided into the following two categories:

Dry method is widely used, and 95% of Zhaohe ALF's output is dry method, which is mainly used in cell phone batteries, MP3, MP4 and other high energy and heavy batteries. In addition, it is also widely used in electric vehicles, aircraft models, and other high-power batteries with high magnification and high capacity. The thermal process can only be applied to batteries with low capacity requirements.

Third, preparation technology of aluminum plastic film

Generally speaking, the preparation of aluminum-plastic film method is divided into dry and thermal bonding two categories:

Dry process: after using adhesive bonding between AL and CPP, direct pressing and into. Advantage is reiterated formability, prevent short circuit performance, appearance (less impurities, pinhole, fisheye), cutting performance. In addition, it’s good resistance to electrolyte and water resistance.

MWCNTS: MPP is then used between AL and CPP, and then under the condition of slow heat booster thermal synthesis, production process is longer than the other. And because the long time high temperature baking effect, make the ALF embrittlement leading to deep performance degradation. The advantages are only in the aspect of resistance to electrolyte and water resistance, and its deep-drawing forming performance, short-circuit prevention performance, appearance, cutting performance are not ideal.

Fourth, the predicament that manufacturer of film of domestic aluminous model faces

At present our country aluminum-plastic film product performance, several technical indexes of only a handful of companies can achieve the level of Japanese companies, the main problems is the electrolyte resistance and impact depth does not pass, the domestic aluminum composite membrane of around 5 mm deep, abroad in 8 mm, 15 mm, even the overall is still some gap with foreign products. Especially the reaction condition and control precision, the high precision of material in the manufacturing process, are often aware that great difference, the difficulty of process control is between exists. At present, the domestic aluminum composite membrane manufacturers there are the following five:

1) Backward surface treatment technology of aluminum foil and serious pollution: serious pollution is caused by washing oil and "chromic anhydride" passivation treatment. At the same time, due to the surface tension of water, the oil in the aluminum foil micropores cannot be cleaned, resulting in defects in subsequent processes.

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

3) The surface of aluminum foil is coated with UV layer, aluminum foil stiffness is not enough, dry method is easy to fold, wide-width products cannot be produced and the yield is poor;

4) For CPP, coating machine is mainly used in China. When combined with aluminum foil surface with high thermal conductivity, it is easy to curl and produce layered crystallization.

5) As a result of the domestic adhesive formula technical reasons, the product is easy to appear the stratification stripping problem.

Domestic lithium battery manufacturers are facing great cost pressure, and urgently need to reduce the cost of lithium battery raw materials. Therefore, the demand for import substitution and localization of aluminum plastic film is increasingly prominent.

The page contains the contents of the machine translation.