Why Aluminum Foil Is Used for the Cathode and Copper Foil for the Anode of Lithium-Ion Batteries

As the use of lithium-ion batteries becomes more widespread, many people are becoming increasingly interested in them. So, why is aluminum foil used for the positive electrode, and copper foil used for the negative electrode in lithium-ion batteries? The main considerations are as follows.

Conductivity and Cost

Among all metals, silver, copper, gold, and aluminum are ranked highest in terms of electrical conductivity. Although silver and gold have excellent conductivity, their high cost makes them unsuitable for large-scale use. Copper and aluminum, on the other hand, have good conductivity and lower costs, making them ideal current collector materials, hence their widespread use in lithium-ion batteries.

Mechanical Performance and Stability

Aluminum foil and copper foil are relatively soft, which is advantageous for winding and bonding during battery manufacturing. Additionally, aluminum foil easily forms a dense oxide film in air, which offers some protection for aluminum in the electrolyte, enhancing its stability. Copper, on the other hand, is relatively stable in the air and, especially in dry air, it hardly reacts. However, if an oxide layer forms on the surface of the copper foil, it can lead to high impedance, which is not favorable for battery production.

Electrochemical Performance

The potential difference between the positive and negative electrodes of a lithium battery determines that aluminum foil is used for the positive electrode, and copper foil is used for the negative electrode. The potential of the positive electrode is higher, and the oxidation potential of aluminum is high. The dense oxide film on the surface of aluminum foil provides good protection for the internal aluminum. Although the oxide layer formed on the surface of aluminum (aluminum oxide) is an insulator and does not conduct electricity, it is very thin, allowing electron conduction through the tunnel effect. However, the oxide layer on the aluminum foil should not be too thick. Copper foil, on the other hand, is easily oxidized at high potential and is therefore not suitable as a positive electrode current collector.

On the other hand, aluminum is prone to alloying reactions with lithium at low potential, making it unsuitable as a negative electrode current collector. Copper maintains structural and electrochemical stability during the battery charge and discharge process, making it suitable as a negative electrode current collector.

In conclusion, the application of copper foil in lithium battery anodes and aluminum foil in cathodes is determined based on the comprehensive consideration of the basic physical properties of copper and aluminum. As a leading company in the copper materials field, Jintian Copper has profound technical experience in copper foil manufacturing. The company is committed to providing high-quality copper foil products for the new energy industry, which are widely used in lithium batteries, electronic components, and electric vehicles.