Lithium-ion Battery Aluminum Foil Materials

The main production process of carbon-coated aluminum foil.

Carbon coating : in this process, the carbon conductive paste is applied to the surface of the aluminum foil after it has been degreased and cleaned in a degreasing and carbon coating box.

Heating and Drying : The aluminum foil coated with carbon conductive paste is passed through a heating and drying box, where clean air is injected to dry the paste.

Carbon-coated aluminum foil is a technological breakthrough in battery conductive substrate surface treatment. It includes nano conductive graphite and carbon-coated particles coated on aluminum foil. The foil provides excellent conductivity and micro-current collection from the active material, reducing contact resistance and improving adhesion while lowering the amount of binder required. Overall, it significantly improves battery performance.

Advantages of carbon-coated aluminum foil in lithium battery applications.

• Inhibiting cell polarization, reducing thermal effects, and improving multiplier performance.
• Reduced cell internal resistance and significantly reduced dynamic internal resistance increase during cycling.
• Improving consistency and increasing the cycle life of the cell.
• Improving the adhesion of the active material to the collector fluid and reducing the cost of pole piece manufacturing.
• Protecting the collector fluid from corrosion by the electrolyte.
• Improving the processing performance of lithium iron phosphate and lithium titanate materials.

The difference between carbon coated aluminum foil and bare aluminum foil for lithium battery applications.

The electrochemical properties of batteries made with carbon-coated aluminum foil and photo aluminum foil differ significantly. The use of carbon-coated aluminum foil improves the internal resistance of the battery, while photo aluminum foil batteries have an additional capacitive resistance arc generated by the double layer capacitance at the interface between the aluminum foil and active material. Carbon-coated aluminum foil also results in less self-discharge and improved storage and power performance, especially at low temperatures.

Furthermore, coated graphene aluminum foil has better performance enhancement on LiFePO4 batteries under high power conditions than coated carbon black aluminum foil due to its better electrical and thermal conductivity along the aluminum foil surface.

For lithium-ion batteries, the commonly used positive collector is aluminum foil and the negative collector is copper foil, both of which require a purity of 98% or more in order to ensure the stability of the collector inside the battery. The main requirement for the collector fluid is to reduce the thickness and weight of the collector fluid. From the intuition to reduce the volume and weight of the battery. In addition, the working principle of lithium battery is a chemical device that converts chemical energy into electrical energy, a medium is needed to transfer the chemical energy into electrical energy, which requires a good conductive material.

Anode (Copper Foil)

Copper foil has good electrical conductivity, soft texture and cheap price. Among the common materials, metal materials are the best conductive materials, and among the metal materials, those with cheap conductivity and good conductivity are copper and aluminum foil. As the battery is relatively coiled, it needs the pole piece to have a certain flexibility to ensure that the pole piece does not break brittle when coiled and other problems, and among the metal materials, copper and aluminum foil are also soft-textured metals. Considering the cost of battery preparation, copper and aluminum foil are inexpensive and abundant in resources.

Cathode (Aluminum Foil)

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. The positive electrode potential is high, and copper foil is easily oxidized at high potential and reacts easily with Li. While the oxidation potential of aluminum is high, the dense oxide film on the surface also has a better protective effect on the internal aluminum. The copper at low potential is also relatively stable, so copper foil is used for the negative electrode and aluminum foil for the positive electrode.

As the energy density of the power battery increases, the aluminum foil as a collector fluid is also becoming thinner and thinner, thus requiring a lower impurity content, less self-discharge, better thickness uniformity, higher surface tension, better bonding performance, thinner thickness, higher strength, higher conductivity, suitable elongation and other requirements, while in order to improve the content of active substances, aluminum foil surface coating technology is also developing rapidly, the following will briefly introduce these new technologies.

Coating technology: the use of functional coating on the battery conductive substrate surface treatment is a breakthrough technological innovation, overlaying carbon aluminum foil is a well-dispersed nano conductive graphite and carbon coated particles, uniformly and delicately coated on the aluminum foil. It provides excellent static conductivity and collects micro-currents from the active material, which can significantly reduce the contact resistance between the material and the collector, and can improve the adhesion between the two, which can reduce the amount of binder used, thus producing a significant improvement in the overall performance of the battery.

Through the coating technology, the stability of the interface can be significantly improved, enhancing the stability of the lithium-ion battery long cycle, has been applied in batch on some power battery products, in addition to this, there are some safety coating technology has gradually begun to apply.

Porous aluminum foil: With the development of technology, porous aluminum foil technology has come into being, which can carry more active materials and allow closer contact between active material particles.

As far as the current technology is concerned, porous aluminum foil has not been applied in large quantities, there are still difficulties in coating, low tensile strength, laminating broken belt, burr more resulting in large self-discharge and so on, further research and solutions are needed, although there are some small soft package data show that can significantly improve energy density, but Lao Li believes that there is still a certain degree of difficulty from industrialization, the need to optimize the pre-process manufacturing process of lithium-ion batteries to match this technology.