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First, copper aluminum foil has good conductivity, soft texture and low price. As we all know, the working principle of lithium battery is an electrochemical device that converts chemical energy into electrical energy. In this process, we need a medium to transfer the electrical energy converted from chemical energy, and conductive materials are needed here. Among ordinary materials, metal materials are conductive materials, while copper foil and aluminum foil are cheap and conductive in metal materials. At the same time, in lithium batteries, we mainly have two processing methods: winding and lamination. Compared with winding, the electrode sheet used to prepare the battery needs to be flexible to ensure that the electrode sheet will not break when winding. Among the metal materials, copper aluminum foil is also a soft metal. Finally, consider the cost of battery preparation. Relatively speaking, copper aluminum foil is relatively cheap, and the world is rich in copper and aluminum resources.

Second, copper aluminum foil is relatively stable in the air. Aluminum easily reacts with oxygen in the air, forming a dense oxide film on the aluminum surface layer to prevent further reaction of aluminum, and this thin oxide film also has a certain protective effect on aluminum in the electrolyte. Copper is relatively stable in the air, and basically does not react in dry air.

Third, the positive and negative pole potentials of lithium batteries determine that the positive pole uses aluminum foil and the negative pole uses copper foil, rather than the reverse. With high positive potential, copper foil is easy to be oxidized at high potential, while aluminum has high oxidation potential, and aluminum foil has a dense oxide film on the surface, which also has a good protection effect on internal aluminum.