PET composite aluminum film and copper foil are good substitutes for traditional lithium battery current collectors (aluminum foil and copper foil). The composite aluminum film is 1 / 2 of the thickness of traditional aluminum foil, and its weight is lighter; The composite copper film is 3 / 4 of the thickness of traditional copper foil, which is also lighter.

It is of great significance to improve the energy density, safety and cost of lithium battery, and has a broad market prospect. Moreover, the technology has great universality, and other composite film materials such as composite copper foil and aluminum foil can also use the technology.

The composite copper foil is made by vacuum depositing copper on the surface of the plastic film with a thickness of 4-6 microns, making a metal layer of about 50-80 nm, metallizing the film, and then thickening the copper layer to 1 micron by aqueous medium electroplating. The overall thickness of the composite copper foil is between 5-8 microns to replace the traditional electrolytic copper foil. PET composite copper foil can save about 2 / 3 of copper, significantly reduce the material cost, and further expand the cost reduction space of the cell.

Compared with traditional copper foil, PET composite copper foil has four advantages:

1. High safety: the plastic diaphragm layer in the middle of the composite copper foil can greatly improve the combustion safety of the battery.

2. High specific capacity: in the same case, the consumption of copper is only 1 / 3-1 / 5 of the original. Some copper is replaced with plastic, which reduces the weight of the battery and increases the energy density of the battery;

3. Long life: reduce the shedding of active substances caused by metal shrinkage and improve the cycle life of the battery;

4. Strong compatibility: suitable for lithium battery environment. The difficulty of technology and process composite fluid collector lies in the close combination of organic polymer and inorganic metal.

The key process can be divided into two steps:

In the first step, vacuum magnetron sputtering, PVD (physical vapor deposition) method is used to sputter a layer of metal with a thickness of 4.5um on the surface of pet,

In the second step, the metal layer on the surface is thickened by ion replacement, and the thickness of copper is about 900 nm.

PVD process is the key of composite collector technology. At present, there are three processes: magnetron sputtering, electron beam evaporation and thermal evaporation. The application of PVD technology in semiconductor field has been relatively mature.

Ion replacement is technically similar to the traditional electroplating method, but the composition of the liquid medicine is relatively simple and only involves copper, a heavy metal.

Electroplating equipment is represented by domestic Dongwei technology and other enterprises. This step is closely connected with the electrolytic copper plating process of traditional copper foil enterprises. Dongwei technology is the leader of precision electroplating equipment in China. Its main products are PCB electroplating special equipment and its supporting equipment, and general hardware electroplating equipment.

Compared with the traditional copper foil process, pet copper plating has the following advantages:

1. The process flow is greatly shortened. The film surface formed by the vacuum coating process is used as the cathode, which can react directly in the ion replacement equipment, and the vacuum process is pollution-free. The copper dissolution and electrolysis process of copper foil also has pollutant emission;

2. A new type of reagent system is adopted to avoid highly toxic substances such as cyanide, so as to better discharge capacity and easier treatment of pollutants in the production process;

3. The antioxidant adopts organic antioxidant liquid, which is directly dried, and the reagent is recycled. The discharge of metal pollutants is avoided.

Source: Changjiang nonferrous metals network