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In order to ensure the stability of the current collector inside the battery, the purity of both is required to be above 98%.With the continuous development of lithium battery technology, whether it is a lithium battery for digital products or a battery for electric vehicles, we all hope that the energy density of the battery is as high as possible, and the weight of the battery is getting lighter and lighter.In the current collector, the most important thing is to reduce the thickness and weight of the current collector, which intuitively reduces the volume and weight of the battery. Why use aluminum foil for the positive electrode of lithium-ion batteries and copper foil for the negative electrode? There are three reasons:
First, copper and aluminum foil has good conductivity, soft texture and low price.
Among ordinary materials, metal materials are the most conductive materials, and among metal materials, copper foil and aluminum foil are cheap and good conductivity.
At the same time, in the lithium battery, we mainly have two processing methods: winding and lamination.Compared with winding, the pole piece used to prepare the battery needs to have a certain degree of flexibility to ensure that the pole piece will not be brittle during winding. Among the metal materials, copper and aluminum foil is also a soft metal.
Second, copper and aluminum foil is relatively stable in the air.
Aluminum easily reacts with oxygen in the air, forming a dense oxide film on the surface of aluminum to prevent further reaction of aluminum, and 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.
The third is that the potential of the positive and negative electrodes of the lithium battery determines the aluminum foil for the positive electrode and copper foil for the negative electrode.The positive electrode potential is high, and the copper foil is easily oxidized at high potential, while the oxidation potential of aluminum is high, and the surface of the aluminum foil has a dense oxide film, which also has a good protective effect on the internal aluminum. Both of them are used as current collectors because they have good electrical conductivity, soft texture (perhaps this will also be conducive to bonding), and are relatively common and cheap. At the same time, a layer of oxide protective film can be formed on the surface of both.
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