Why does lithium battery use copper foil for cathode?

The lithium battery utilizes lithium ions stored in the positive electrode material and electrons to reversely move during charging and discharging to achieve normal operation. The main structures are a positive electrode, a negative electrode and an electrolyte. In addition to most of the major outer four, used to store the positive and negative electrode current collector material is a lithium battery important part, its main function is to generate the current of the battery active material brought together to form a larger external output current. According to the working principle and structural design of the lithium ion battery, the positive electrode and the negative electrode material should be coated on the conductive current collector, so the current collector should be in full contact with the active material, and the internal resistance should be as small as possible.

Copper foil and aluminum foil have good conductivity, have formed oxidized protective film, soft texture is favorable for bonding, mature manufacturing technology and relatively low price, so they are selected as the main material of lithium battery current collector. The positive electrode potential of the lithium battery is high, the oxide layer of the aluminum foil is relatively dense, and the current collector can be prevented from being oxidized, and the lithium intercalation reaction occurs at a high potential, and the positive current collector is not suitable. The positive current collector generally uses aluminum foil; and the negative electrode has a low potential. The aluminum foil is easy to form an aluminum-lithium alloy at a low potential, and the anode current collector generally uses a copper foil, and the copper foil and the aluminum foil do not have an inter-changeability.

After the negative electrode active material of the battery is uniformly mixed with about 90% of the negative electrode active material carbon material, 4% to 5% of acetylene black conductive agent, and 6% to 7% of the binder, the negative electrode active sauce is generally uniformly distributed. It is coated on the surface of the copper foil current collector, and the active material has a thickness of 50-100 m. The negative electrode is obtained by drying, rolling, slitting and the like. The basic performance of a lithium battery is closely related to the material of the entire battery system. For the negative electrode, in addition to the negative active material, the quality of the copper foil also has a great influence on the negative electrode fabrication process and battery performance.

A lithium-ion copper foil which is a current collector of a lithium battery generally has a thickness of between 7 and 20 μm. At present, the thickness of the copper foil of the new energy vehicle is 8~12μm, and the quality of the whole vehicle copper foil is more than 10kg. The smaller the thickness of the lithium copper foil, the lighter the weight of the battery. At the same time, thinner lithium-ion copper foil also means smaller resistance, and the performance of the battery will also be improved. Therefore, reducing the quality of the copper foil on the battery, reducing the cost of the copper foil raw material, and providing a higher energy density, become the key to the copper foil for the power lithium battery. We believe that the use of lighter and thinner lithium foil in the future is a major trend.