Why are the anode plates of lithium-ion batteries aluminum foil?

Why does lithium ion battery use aluminum foil as the anode, while copper foil as the cathode? There are three reasons:

One is the copper foil good electrical conductivity, texture soft, price is cheap. As we all know, the lithium battery working principle is a kind of electrochemical convert chemical energy into electrical energy device, so in the process, we need a medium that the chemical energy into electrical energy transfer, here requires conductive materials. And in ordinary material, metal material is the best material and electrical conductivity in metal material is cheap electrical conductivity and good copper foil and aluminum foil. At the same time, in lithium battery we are winding and laminated two kinds of processing methods. Relative to the winding, the need for the preparation of battery pole piece has certain flexibility, to ensure that pole piece don't produce the problem such as brittle fracture when coiling, metal materials, copper and aluminum foil and quality of a material soft metal. Finally is consider battery preparation cost, relatively speaking, copper foil price is relatively cheap, copper and aluminum in the world is rich in resources.

Second, the copper foil was relatively stable in the air. Aluminium is easy to react with oxygen in the air, and the oxide film was prepared on aluminum surface, to prevent further reaction of aluminium, and this very thin layer of oxide film of aluminum in the electrolyte has certain protective effect. Copper in itself is relatively stable in the air, little or no response in the dry air.

The third is lithium battery is the cathode potential decides the anode aluminum foil, the cathode copper foil, not the other way round. The anode potential is high, the copper foil is easy to oxidation under high voltage, high oxidation potential, and aluminum and the aluminum foil surface layer and the oxide film has, also has good protection for the internal aluminum.

For lithium ion batteries, the positive set of the fluid in common use is aluminum foil, fluid is copper foil negative set, in order to guarantee stability of fluid inside the cell, the purity requirements both in more than 98%.With the continuous development of lithium-ion battery technology, regardless of whether they are used in digital products lithium-ion batteries or the batteries of electric cars, we all hope the battery energy density is high, as far as possible the weight of the battery is more and more light, and in the collector, the most main is to reduce the thickness and the weight of the fluid, up from intuitive to reduce the volume and weight of the battery.

Li-ion battery with copper foil thickness requirements

Along with the rapid development in recent years, lithium electricity, lithium battery with set fluid development also soon. The anode aluminum foil by a few years ago the 16 reduced to 14 um, um to 12 um, now has many battery manufacturers have production using 10 um foil, even use 8 um. And the cathode copper foil and copper foil flexibility is good, because itself by its thickness before 12 um um reduced to 10, to 8 um, up to now there is a big part of the battery manufacturer to mass produce with 6 um, and some of the manufacturers are developing 5 um / 4 um are likely to use. Due to the lithium battery for use of copper foil are high purity, the density of material basic on the same level, with the loss of the thickness of the development, its surface density is reduced, the weight of the battery is also more and more small, in accordance with our demand for lithium batteries.

Li-ion battery with copper foil surface roughness requirements

As for current collector, besides its thickness and weight will be influential to lithium batteries, the surface performance of current collector has a great influence on production and performance, especially negative electrode current collector. Due to the defects of preparation technology, the market of copper foil mainly has single-sided, double-sided, double-sided coarsening MAO varieties. The two negative sides coating has asymmetric contact with resistance caused by asymmetric structure asymmetry, and then make two negative capacity cannot even release; besides, the two sides asymmetry also cause negative electrode coating bond strength, unbalanced charge-discharge cycle life of anode coating on both sides, which accelerates the battery capacity attenuation.

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