Why Lithium Battery Positive Electrodes Are Made of Aluminum and Electrodes of Negative Electrodes
1. The use of both as current collectors is due to their good electrical conductivity, relatively soft texture (which may also be beneficial for bonding), and relatively inexpensive and relatively common, both of which form an oxide protective film on the surface. .
2, copper / nickel surface oxide layer belongs to the semiconductor, electronic conduction, oxide layer is too thick, large resistance; and aluminum oxide layer on the aluminum oxide is an insulator, the oxide layer can not be conductive, but because of its thin, through the tunnel effect of electronic Conductance, if the oxide layer is thicker, the aluminum foil is poorly conductive and even insulated. Generally, the current collector is preferably subjected to surface cleaning before use. On the one hand, the oil is washed away, and the thick oxide layer can be removed.
3, high anode potential, aluminum thin oxide layer is very dense, to prevent oxidation of the current collector. The copper/nickel foil oxide layer is looser. In order to prevent its oxidation, the potential is relatively low. At the same time, Li is difficult to form a lithium intercalation alloy with Cu/nickel at a low potential, but if the copper/nickel surface is heavily oxidized, it is slightly higher. At the potential Li will react with copper oxide/nickel intercalation. Aluminum foil cannot be used as a negative electrode, and LiAl alloying occurs at a low potential.
4. The current collector requires pure components. Impurities in Al can lead to the occurrence of pitting due to the non-dense surface film, and even to the formation of LiAl alloys due to the destruction of the surface film.