Copper and aluminum are the most commonly used material […]
Copper and aluminum are the most commonly used materials for anode and cathode current collectors, respectively. Among them, aluminum foil is easier to form an oxide film on the surface regardless of whether it is in the air or in the electrolyte. At the same time, the overall corrosion and local corrosion (such as pitting) and poor adhesion of the current collector surface will increase the electrode reaction resistance. , The internal resistance of the battery increases, resulting in a loss of capacity and a decrease in discharge efficiency. In order to reduce the influence caused by these reasons, the current collectors purchased from the market should be pretreated (acid-alkali corrosion, corrosion-resistant coating, conductive coating, etc.) to improve corrosion resistance and adhesion performance. Because the surface adhesion of the current collector is too small, the electrode may be partially separated from the current collector, which increases the polarization effect and greatly affects the capacity. The copper current collector corrodes during use to form a layer of insulating corrosion product film. As a result, the internal resistance of the battery increases and the discharge efficiency decreases during the cycle, resulting in a loss of capacity. When over-discharged, the copper foil will react as follows:
Cu → Cu + + e- produced Cu (I)
When charging, it will crystallize and deposit in the form of metallic copper on the surface of the negative electrode, forming copper dendrites, which can easily penetrate the diaphragm and cause a short circuit or even an explosion. Pay special attention to the fact that when choosing the negative pole piece, it is absolutely not allowed to have the pole piece with the exposed copper, otherwise the pole piece at the exposed copper will easily generate dendrites and damage the alkaline battery . To prevent the dissolution of the copper current collector, the discharge voltage should not be lower than 2.5V.