0.01mm gold-plated copper foil and PET copper foil are mainly used as battery current collector materials

1、 Introduction to PET Copper Foil
    PET copper foilMainly used as a battery current collector material, it mainly collects current, and the active material is mainly some powder like particles, which also require some mechanical strength to support the internal powder particles. From a cost perspective, aluminum and copper are cheaper. The physical performance is decent. Aluminum foil for positive electrode current collector and copper foil for negative electrode current collector are currently the optimal solutions for batteries, and aluminum can be used for both the positive and negative poles of sodium ions. At present, the production of copper foil is mainly based on lamination, while aluminum foil is mainly rolled. The fine processing of aluminum foil in China is not very good, but the lamination of copper foil is still relatively excellent in China.
    Copper foil and aluminum foilThe trend is to make it thinner and thinner, mainly to increase energy density. The shape of PET copper foil is similar to a sandwich style, with two layers of copper on the outside and PET on the inside.
2、 Production process of PET copper foil
We use PVD and electroplating methods to make copper foil. Firstly, copper coating was carried out on PET film using target sputtering, with 4 μ m PET and 1 μ m copper, totaling 6 μ m, matched with pure copper foil in the battery. The thicker the coating, the better the conductivity. Although target sputtering promotes better bonding between copper and PET, the efficiency is too low, with only a few tens of nanometers per sputtering and 20-30 times required for 1 μ m.
Later on, we used vacuum evaporation to condense the evaporated metal onto PET film, which can produce uniformly and has a relatively high efficiency, twice that of sputtering. The difficulty of this technology lies in the high evaporation temperature of the metal, while the temperature resistance of PET film is only over 200 degrees, and a slight temperature difference can cause it to burn through.
We are making both aluminum and copper, and aluminum has reached its technological limit. Copper can be deposited using electrolysis. Place the sputtered/evaporated PET copper substrate into an electrolytic cell for growth. The main difficulty lies in the need for two sets of electrode circuits to ensure consistent copper foil thickness on both sides.

3、 Advantages of PET copper foil:
(1) High safety: Currently, current collectors mainly consist of copper foil and aluminum foil, which are prone to breakage when subjected to stress. Once broken, they can easily puncture the diaphragm, causing internal short circuits and leading to uncontrolled heating. PET is not easy to break, and it is also not easy to puncture PET film after metal fracture.PET copper foilIn the puncture test, it is possible to achieve a state of only smoking and not catching fire,
(2) Improving energy density: PET material is lighter, so the overall weight of PET copper foil is smaller, which is 1/4 of copper (equivalent to replacing the middle part of the metal foil with a layer of PET), reducing the weight of the battery and improving its energy density. Can increase energy density by 5-10%.
(3) Longevity: Forming a swollen sponge body that absorbs stress during expansion, resulting in a 5% increase in lifespan.
(4) Strong compatibility: Suitable for batteries of different specifications and systems.

    PET copper foilThe production process is mainly two-step, first using magnetron sputtering technology to achieve non-metallic material metallization; Then, the water electroplating process is adopted to meet the conductivity requirements of the current collector, which is a difficult process. PET copper foil has the characteristics of low density, thin thickness, and high tensile strength. Coupled with its good conductivity, it has the potential to replace traditional lithium battery copper foil in lithium-ion batteries.

More and more enterprises are entering the PET copper foil market, and the industrialization process is expected to accelerate. In terms of upstream, companies that have already entered the market include Sanfu Xinke, which is currently promoting the application testing of PET copper plating specialty chemicals. In terms of midstream, currently included companies include Chongqing Jinmei, Shuangxing New Materials, Wanshun New Materials, Baoming Technology, etc. Chongqing Jinmei and Baoming Technology have entered the mass production stage or have mass production plans. The polymer composite copper film independently developed by Chongqing Jinmei has been successfully applied to new energy vehicle batteries and has passed the German puncture experiment, entering the mass production stage. In addition, in 2021, the company invested 220 million yuan to expand its production capacity of 36 million square meters per year for composite aluminum film and 36 million square meters per year for composite copper film. In July 2022, Baoming Technology announced plans to invest 6 billion yuan to build a lithium battery composite copper foil production base in Ganzhou.
PET copper foil is a type ofComposite copper foilIt has a sandwich structure of copper polymer copper composite. Firstly, a PET (polyethylene terephthalate) polymer film is used as the substrate, and then a metal copper layer is deposited on both sides of the PET film using advanced technology. The thickness of composite copper foil base material is generally 3-8 μ m. Then, a layer of 30-70 nanometer metal layer is made on both sides of the base film, and the metal layer is thickened to 1 μ m or more by thickening. Therefore, the thickness of composite copper foil is generally 5-10 μ m, which can be used to replace 4.5-9 μ m electrolytic copper foil. PET copper foil is made of 4.5 μ m PET as the base film, and then coated with 1 μ m copper on each side of the base film, forming a 6.5 μ m PET copper foil.