Why do we use copper foil for the negative electrode and aluminum foil for the positive electrodel

In lithium batteries, the main reason for using copper foil for the negative electrode and Aluminum Foil for the positive electrode is their physical and chemical properties. In order to ensure the stability of the collector fluid inside the battery, the purity of both is required to be above 98%. Why the positive electrode of lithium-ion batteries uses aluminum foil, and the negative electrode uses copper foil, there are four reasons:

Different physical and chemical properties

Copper foil has good electrical and thermal conductivity, which can effectively improve the energy density and charge and discharge efficiency of the battery. In addition, the copper foil also has good mechanical strength and flexibility, which can meet the deformation and expansion requirements of the battery during the charging and discharging process.

In terms of chemical properties, it is mainly because the copper foil can provide a stable electrode potential in the electrochemical reaction, thus ensuring the stability and safety of the battery. In addition, the copper foil can also form good contact with the negative electrode material to improve the charge and discharge efficiency of the battery.

Aluminum foil has high specific strength and good ductility, which can meet the expansion and contraction requirements of the battery during the charging and discharging process. In addition, aluminum foil also has good corrosion resistance and oxidation resistance, which can improve the service life of the battery.

In terms of chemical properties, it is mainly because aluminum foil can provide a higher electrode potential in electrochemical reactions, thereby improving the energy density and charge and discharge efficiency of the battery. In addition, aluminum foil can also form good contact with the positive electrode material, improving the charge and discharge efficiency of the battery.

Good electrical conductivity, soft texture, cheap price

The working principle of lithium battery is an electrochemical device that converts chemical energy into electrical energy, so in this process, we need a medium to transfer the electrical energy converted by chemical energy, here we need conductive materials. In ordinary materials, metal materials are the best materials for electrical conductivity, and in metal materials, the price is cheap and the conductivity is good: copper foil and aluminum foil. At the same time, in lithium batteries, we mainly have two processing methods: winding and laminating. Relative to the winding, the electrode sheet used for the preparation of the battery needs to have a certain softness to ensure that the electrode sheet does not occur in the winding brittleness and other problems, and the metal material, copper aluminum foil is also a soft metal. Finally, consider the cost of battery preparation, relatively speaking, the price of copper aluminum foil is relatively cheap, and the world's copper and aluminum resources are rich.

The copper aluminum foil is relatively stable in the air

Aluminum is easy to chemically react with oxygen in the air, generating a dense oxide film on the surface layer 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 the air and basically does not react in dry air.

The electrode potential is different

The positive and negative potentials of lithium batteries determine the positive electrode with aluminum foil and the negative electrode with copper foil. The positive electrode potential is high, and the copper foil is easy to be oxidized at a high potential, while the oxidation potential of aluminum is high, and the surface layer of aluminum foil has a dense oxide film, which also has a good protective effect on the internal aluminum. Both are used as fluid collectors because they have good electrical conductivity, are relatively soft in texture (which may also be conducive to bonding), are relatively common and inexpensive, and both can form an oxide protective film on the surface.