Positive and negative current collectors for -Lithium - Ion Battery Equipment

Positive and negative current collectors for lithium batteries -Lithium - Ion Battery Equipment

It is well known that the four important parts of lithium batteries are positive electrode material, negative electrode material, separator and electrolyte. However, in addition to the four important parts, the current collector used to store the positive and negative materials is also an important part of the lithium battery. Today we will talk about the positive and negative current collector materials of lithium batteries.

1. Basic information of collectors

For lithium batteries, the commonly used positive current collector is aluminum foil, and the negative electrode current collector is copper foil. In order to ensure the stability of the current collector inside the battery, the purity of both is required to be above 98%. With the continuous development of lithium battery technology, whether it is a lithium battery for digital products or a battery for electric vehicles, we all hope that the energy density of the battery is as high as possible, and the weight of the battery is getting lighter and lighter, and the most important thing in the current collector is Reducing the thickness and weight of the current collector intuitively reduces the volume and weight of the battery.(Lithium - Ion Battery Equipment)

1. Thickness requirements of copper and aluminum foil for lithium batteries

With the rapid development of lithium batteries in recent years, the current collectors for lithium batteries have also developed rapidly. The positive aluminum foil has been reduced from 16um in previous years to 14um, and then to 12um. Now many battery manufacturers have mass-produced aluminum foil that uses 10um, and even uses 8um. As for the copper foil used for the negative electrode, due to the good flexibility of the copper foil itself, its thickness has been reduced from 12um to 10um, and then to 8um. At present, most battery manufacturers use 6um for mass production, and some manufacturers are developing 5um/4um are all possible. Due to the high purity requirements of the copper-aluminum foil used in lithium batteries, the density of the material is basically at the same level. As the development thickness decreases, its areal density also decreases accordingly, and the weight of the battery is naturally getting smaller and smaller, which is in line with our lithium batteries. need.

2. Surface roughness requirements of copper and aluminum foil for lithium batteries

Regarding the current collector, in addition to the influence of its thickness and weight on the lithium battery, the surface properties of the current collector also have a great influence on the production and performance of the battery. Especially for the negative electrode current collector, due to the defects of the preparation technology, the copper foils on the market are mainly single-sided wool, double-sided wool, and double-sided roughened varieties. This asymmetry of the two-sided structure leads to asymmetric contact resistance of the coating on both sides of the negative electrode, which in turn makes the capacity of the negative electrode on both sides unable to be released uniformly; at the same time, the asymmetry of the two sides also leads to inconsistent bonding strength of the negative electrode coating, yes, the charge-discharge cycle life of the negative electrode coating on both sides Serious imbalance, which in turn accelerates the decay of battery capacity.

In the same way, the positive aluminum foil is also developed to a double-sided symmetrical structure as much as possible, but currently affected by the aluminum foil preparation process, it is important to use a single-sided smooth aluminum foil. Since aluminum foil is basically rolled from thick aluminum ingots, the contact between the aluminum ingot and the roll should be controlled during the rolling process, so lubricants are generally added to the surface of the aluminum foil to protect the aluminum ingot and the roll. The lubricant on the surface has a certain influence on the battery pole piece. Therefore, for aluminum foil, the removal of lubricant from the surface is also a key factor.

3. Why use copper foil for negative electrode and aluminum foil for positive electrode?

First, copper and aluminum foil has good conductivity, soft texture and low price. We all know that the working principle of lithium batteries is an electrochemical device that converts chemical energy into electrical energy. In this process, we need a medium to transfer the electrical energy converted from chemical energy, and here we need conductive materials. Among ordinary materials, metal materials are the most conductive materials, and among metal materials, copper foil and aluminum foil are cheap and good conductivity. At the same time, in the lithium battery, we mainly have two processing methods: winding and lamination.



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