Five major materials of lithium ion battery: positive machine material; negative electrode material; electrolyte; lithium battery separator; aluminum-plastic composite film. Among them, there are more reports on positive and negative materials, electrolytes and lithium battery separators, and there are more domestic enterprises. However, the "profitable" material of aluminum-plastic composite membrane has been neglected for various reasons for a long time.
According to statistics, in 2013 China produced 3.5 billion batteries annually, and the consumption of aluminum-plastic composite films was 50-60 million square meters.
Lithium polymer battery is the battery with the highest capacity, the lightest weight and the highest safety among lithium batteries. In shape, the lithium polymer battery has the characteristics of ultra-thin, which can be made into batteries of any shape and capacity to meet the needs of various products. This type of battery can reach a minimum thickness of 0.5mm. Its nominal voltage and Li -ion ​​is also 3.6 or 3.7V, no memory effect.
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Polymer soft pack batteries are deeply loved by digital products, and will also be the mainstream direction of wearable lithium batteries in the future.
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At present, products such as: i-Watch, i-PAD, Huawei ’s mate-7, and Xiaomi ’s mobile phones basically use polymer soft pack batteries. One of the important components of polymer soft pack batteries is aluminum plastic. Composite membrane.
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Structure of aluminum-plastic composite membrane
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The aluminum-plastic film is composed of five layers: outer nylon layer / adhesive / intermediate aluminum foil / adhesive / inner layer heat seal layer, and each layer has relatively high functional requirements.
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There are only a few manufacturers of domestic aluminum plastic film, some of which have reached the DNP index, most of which are battery liquid resistance and deep drawing, but the domestic drawing is about 5mm, which is generally good. Foreign countries can generally reach 8mm, and more Even reached 15mm. It can be seen that the domestic performance needs to be improved.
The performance of domestic aluminum plastic film lags behind
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At present, the domestic aluminum plastic film is used in the lithium battery industry, but there are basically no performance products, only a few experimental products.
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The main constraints are: the insufficient stretch rate of domestic aluminum foil, and the supporting BOPA (bidirectional stretch nylon) production enterprises have not really invested in the relevant technology, which makes the two materials cannot be unified.
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Disadvantages of Chinese aluminum-plastic composite membrane:
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1. The surface treatment process of aluminum foil is backward, and it is degreased by water washing and passivation treatment of "chromic anhydride", which causes great pollution. The water has surface tension and the oil in the pores of the aluminum foil is not cleaned, which causes defects in the subsequent compounding process.
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2. The aluminum foil after water treatment will produce "hydrogen embrittlement", which causes the folding resistance of domestic aluminum-plastic composite film to never reach the Japanese level.
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3. The CPP polymer is directly cast on the aluminum foil with no stretch orientation on the surface. The high heat polymer encounters the surface of the high thermal conductivity aluminum foil and curls rapidly, producing layered crystals, resulting in more defects.
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4. The UV layer is not coated on the surface of the aluminum foil, which results in insufficient stiffness of the aluminum foil. The dry composite is easy to wrinkle and cannot be used for wide-format products. The scrap rate is extremely high.
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The raw materials of aluminum-plastic films, whether they are aluminum foil or BOPA, have huge domestic production capacity, and can even be described as overcapacity. However, aluminum-plastic films for lithium batteries still need to be imported from Japan.
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A simple account is calculated. At present, the price of aluminum foil for air conditioners sold by domestic enterprises is 4400 / ton, the price of aluminum-plastic composite film made in Japan is 24-42 yuan / ㎡, the thickness is 45um, and the thickness of one kilogram of aluminum is 45um and the thickness is 300㎡. After calculation, the price of a meal of aluminum-plastic film is about 10 million (7.2 million to 12.6 million).
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The same ton of aluminum products, on the one hand, is the unsalable 4,400 yuan, and on the other is the arrogant 10 million. The market for aluminum-plastic films for lithium batteries should not be ignored anymore!
Source of this article: unima new material network
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