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Why do lithium batteries use copper foil for anode and aluminum foil for cathode

Why do lithium batteries use copper foil for anode electrodes and Aluminum Foil for cathode electrodes?

For lithium ion batteries, the commonly used positive electrode current collector is aluminum foil, and the negative electrode current collector is copper foil. In order to ensure the stability of the current collector in the battery, the purity of both is required to be above 98%.

There are three reasons why the positive electrode of lithium ion battery uses aluminum foil and the negative electrode uses copper foil:

1.Copper foil and aluminum foil have good conductivity, soft texture and cheap price.
We all know that the working principle of a lithium battery is an electrochemical device that converts chemical energy into electrical energy. Then in this process, we need a medium to transfer the electrical energy converted from chemical energy. Here, conductive materials are needed.Among ordinary materials, metal materials are the materials with the best conductivity, and among metal materials, the cheaper and better conductive materials are copper foil and aluminum foil. At the same time, in lithium batteries, we mainly have two processing methods: winding and lamination. Relative to winding, the pole piece used to prepare the battery needs to have a certain degree of flexibility to ensure that the pole piece does not suffer from brittle fracture during winding. Among metal materials, copper and aluminum foil are also softer metals. The last is to consider the cost of battery preparation. Relatively speaking, the price of copper and aluminum foil is relatively cheap, and the world is rich in copper and aluminum element resources.
Battery Grade Copper Foil
2.Copper and aluminum foil are 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. This thin oxide film also has a certain protective effect on aluminum in the electrolyte. Copper itself is relatively stable in air, and basically does not react in dry air.
Battery Grade Aluminum Foil

3.The positive and negative electrode potentials of lithium batteries determine the aluminum foil for the positive electrode and the copper foil for the negative electrode, not the other way around. 

The positive electrode potential is high, copper foil is easily oxidized at high potential, and aluminum has a high oxidation potential, and the aluminum foil surface has a dense oxide film, which also has a good protective effect on the internal aluminum. Both are used as current collectors because they have good electrical conductivity and relatively soft texture (maybe this will also help bonding), and are relatively common and relatively cheap. At the same time, an oxide protective film can be formed on both surfaces.

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