Don't send (Guo Hui) study on corrosion resistant Composite Aluminum foil for Aluminum plastic Film of New Energy Automobile flexible package Battery for the time being [Automotive Materials Summit]

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At the 2021 China Industry Expo New Materials Forum and China Automotive New Materials Application Summit Forum held by SMM, Guo Hui, aluminum alloy developer of Shanghai Huafeng material Science and Technology Research Institute, introduced the research of corrosion-resistant composite aluminum foil for aluminum-plastic film of new energy automobile flexible package battery.

Background

The power battery has a high demand for power, which will produce a lot of heat in the working process, and the battery heating is easy to cause battery failure or even explosion. In order to improve the heating state of the battery, the structure of the battery was improved, and the actual working environment of the battery was designed as the antifreeze system, which is different from the atmospheric environment of the traditional flexible packaging of lithium battery. therefore, a new requirement is put forward for the corrosion resistance of aluminum foil for flexible packaging composite film of lithium-ion battery, that is, aluminum foil should be able to withstand the corrosion of antifreeze system for a long period and ensure the reliability of the overall structure of the material.

Through the design of double-layer aluminum alloy composite structure, the outer structure can replace nylon. By means of sacrificing anode, the protective layer material is designed to improve the corrosion rate of the material, and the material of the core layer is optimized at the same time to improve the strength and deformability of the material.

Effect of Zn element Diffusion on corrosion Resistance of Materials

The line scanning results of Zn elements show that before annealing, the Zn element in the protective layer does not diffuse to the core layer, but after annealing, the Zn element diffuses from the protective layer to the core layer, and the diffusion distance increases with the extension of annealing time.

Due to the diffusion of the Zn element, the corrosion potential shows a continuous gradient distribution with the change of the distribution state of the Zn element. Even if the change of the corrosion potential between the protective layer and the core layer shows a continuous change, the corrosion potential changes continuously, and a weak corrosion couple is formed between the protective layer and the core layer, thus weakening and homogenizing the corrosion and reducing the occurrence of pitting corrosion to a certain extent. Promote the uniform corrosion of the material, so as to effectively reduce the corrosion rate.

Effect of annealing process on recrystallization ratio

After annealing, the Zn element diffuses from the protective layer to the core layer, the concentration of the Zn element shows a continuous gradient change, and the corrosion potential also shows a continuous gradient distribution, even if the corrosion potential between the protective layer and the core layer shows a continuous change, the continuous change of the corrosion potential, the continuous gradient change of the corrosion potential can reduce the occurrence of pitting corrosion to a certain extent and promote the uniform corrosion of the material. As a result, the corrosion rate can be effectively reduced.

Summary

(1) different Zn element content will lead to different diffusion distance in the heating process, and will also affect the remaining Zn element content in the protective layer after annealing. When the Zn element content is 4%, a better concentration gradient between the protective layer and the core layer can be obtained, thus slowing down the corrosion rate of the material. After the OY corrosion experiment, the material is thinned for 5-7 mm, with better corrosion resistance.

(2) both low temperature for a long time and high temperature for a short time can effectively maintain the mechanical properties of the material, and the properties are stable in the directions of 0 °, 45 °and 90 °, which is beneficial to deep drawing deformation.