Why is aluminum foil used for the positive electrode of lithium-ion batteries, while copper foil is used for the negative electrode?
Release time:
Jul 14,2023
1. Copper aluminum foil has good conductivity, soft texture, and low price.
2. Copper aluminum foil is also relatively stable in the air.
3. The positive and negative electrode potentials of lithium batteries determine the use of aluminum foil for the positive electrode and copper foil for the negative electrode, rather than the opposite. The positive electrode potential is high, and copper foil is easily oxidized at high potentials, while aluminum has a high oxidation potential, and the surface of the aluminum foil has a dense oxide film, which also has a good protective effect on the internal aluminum.
The size of the lattice Octahedron void of metallic aluminum is similar to that of Li, and it is very easy to form metal interstitial compounds with Li. Li and Al not only form an alloy with the chemical formula LiAl, but also may form Li ≮ Al ₂ or Li ₄ Al ∨.
Due to the high reactivity of the reaction between metal Al and Li, metal Al consumes a large amount of Li, and its structure and morphology are also damaged, so it cannot be used as a collector for the negative electrode of lithium-ion batteries; During the charging and discharging process of the battery, Cu only has a small amount of lithium intercalation capacity and maintains stability in its structure and electrochemical performance, making it suitable as a collector for the negative electrode of lithium-ion batteries.
At 3.75V, the polarization current of Cu foil begins to significantly increase and increases linearly, leading to intensified oxidation, indicating that Cu begins to become unstable at this potential; However, the polarization current of aluminum foil is small and constant throughout the entire polarization potential range.
No obvious corrosion phenomenon was observed, maintaining stable electrochemical performance. Due to the small lithium intercalation capacity of Al in the positive electrode potential range of lithium-ion batteries and its ability to maintain electrochemical stability, it is suitable for use as a positive electrode current collector for lithium-ion batteries.
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