the positive and negative electrodes of Lithium - ion Batteries, respectively

In this era of rapid technological development, lithium-ion batteries are widely used in all aspects of our lives due to their outstanding performance. They can be found everywhere, from smartphones to electric vehicles. So, have you ever wondered why aluminum foil is used for the positive electrode and copper foil for the negative electrode of lithium-ion batteries? Today, let's lift the mysterious veil together.

I. The Perfect Balance between Conductivity and Cost

Among numerous metals, silver, copper, gold, and aluminum rank high in terms of conductivity. However, although silver and gold have extremely excellent conductivity, their high costs make large-scale applications impractical. In contrast, copper and aluminum not only have good conductivity but also are relatively low in cost, making them ideal collector materials. It's just like when we are building something, we need to choose materials that are both sturdy and affordable. Copper and aluminum play such roles in lithium-ion batteries.
II. Excellent Mechanical Properties and Stability
Aluminum foil and copper foil are soft in texture, which has a great advantage in the battery manufacturing process. They are like soft fabrics that can be easily wound and bonded, facilitating the production of batteries.

Meanwhile, aluminum foil easily forms a dense oxide film in the air. This oxide film is like a solid armor, which plays a good protective role for aluminum in the electrolyte and greatly enhances the stability of the aluminum foil. Copper is relatively stable in the air, especially in dry air where it hardly reacts. However, if an oxide layer forms on the surface of copper foil, it will lead to relatively high impedance, which is very unfavorable for battery production.
III. Unique Electrochemical Properties

The potential difference between the positive and negative electrodes of lithium-ion batteries determines the different uses of aluminum foil and copper foil. The potential of the positive electrode is relatively high, and the oxidation potential of aluminum is also high. Moreover, the dense oxide film on the surface of aluminum foil provides good protection for the internal aluminum. Although this oxide film, aluminum oxide, is an insulator and cannot conduct electricity, it is so thin that electron conduction can be achieved through the tunneling effect. However, the oxide layer on the surface of aluminum foil should not be too thick, otherwise it will affect the electron conduction efficiency.

On the other hand, copper foil is prone to oxidation at high potentials, so it is not suitable for use as a positive electrode collector. Aluminum is prone to alloying reactions with lithium at low potentials, so it is also not suitable for use as a negative electrode collector. In contrast, copper can maintain the stability of its structure and electrochemical properties during the charging and discharging process of the battery, making it very suitable for use as a negative electrode collector.

In conclusion, through a comprehensive consideration of the basic physical properties of copper and aluminum, we have determined the application of copper foil in the negative electrode and aluminum foil in the positive electrode of lithium-ion batteries. This choice not only ensures the performance and stability of lithium-ion batteries but also provides powerful power support for our technological lives. Let's look forward to more surprises that lithium-ion batteries will bring us in the future!