PET coated current collector is an important research direction

PET coatingIt is a new type of power battery current collector material with a composite foil structure. The middle layer of PET copper foil is made of polyethylene terephthalate (PET) conductive film, and the two sides of the conductive film are metal coatings with a thickness of 1-2m. The preparation steps include at least vapor deposition of first/second/third metal layers, composite first/second/third thin films, etching, roll pressing, etc. The complexity of the process is higher than that of traditional lithium foil materials.

Figure 19: Preparation process of PET electroplated copper foil

Source: "Preparation Method of Conductive Thin Film and Lithium ion Battery", Research Department of China International Capital Corporation

The key preparation steps of PET electroplating have high requirements for industry technology. The manufacturing difficulty of PET coating lies in the tight combination of organic polymers and inorganic metals. The key process mainly consists of two steps. The first step is to use physical vapor deposition to sputter a layer of metal on the surface of PET, and the second step is to use ion displacement (similar to traditional electroplating technology) to thicken the surface metal layer. The above two key steps have high quality requirements for sputtering process parameters and plating solution. In the sputtering process, equipment design and manufacturing technology, process technology, and control technology will significantly affect the film formation rate and film adhesion. In the copper plating process, the temperature of the plating solution PH、 The concentration and other reaction conditions have a significant impact on the weight gain rate of copper plating and the surface morphology of copper plated samples.

Compared to traditional metal foils, PET electroplated foils provide better safety guarantees due to their structural properties and also perform better in safety testing results.

Composite foil materialThe medium plastic separator layer helps to improve the combustion safety of batteries. During the process of battery charging and discharging, the volume of negative electrode material changes accordingly. Traditional lithium battery foil materials will constantly stretch and shrink, and the positive and negative electrode materials may fall off, causing a decrease in capacity, performance, increased resistance, increased heat generation, and other safety hazards. In addition, there is a safety risk of battery explosion due to damage caused by dendrite growth, external forces, and other factors leading to thermal runaway. When the battery experiences thermal runaway, the plastic diaphragm layer of the composite foil material can generate significant resistance in the event of circuit thermal runaway, reducing the risk of battery combustion and fire.