Lithium ion batteries, as a new generation of green and high-energy rechargeable batteries, have outstanding advantages such as high voltage, high energy density, good cycling performance, low self discharge, and no memory effect. They have achieved rapid development in the past 10 years and have dominated the field of mobile electronic terminal devices such as laptops, mobile phones, cameras, weapons and equipment in various countries around the world with their excellent cost-effectiveness. They are considered a high-tech industry of great significance to the national economy and people's lives in the 21st century.
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, which requires conductive materials. Among ordinary materials, metal materials have the best conductivity, while copper foil and aluminum foil are cheaper and have good conductivity among metal materials. Meanwhile, in lithium batteries, we mainly have two processing methods: winding and stacking. Compared to winding, the electrode sheets used for preparing batteries need to have a certain degree of flexibility to ensure that the electrode sheets do not suffer from brittle fracture during winding. However, in metal materials,For double-sided lithium-ion batteries
Electrolytic copper foil
It is also a metal with a relatively soft texture. Finally, considering the cost of battery preparation, copper aluminum foil is relatively inexpensive and has abundant resources of copper and aluminum elements.
Copper foil is not only the carrier of negative electrode active material in lithium-ion batteries, but also the collector and conductor of negative electrode electrons. Therefore, it has special technical requirements, which include good conductivity, uniform coating of negative electrode material on the surface without peeling off, and good corrosion resistance. To ensure the coating is appliedElectrolytic copper foilThe negative electrode material on top will not fall off, and a suitable binder must be added during preparation. According to Coating Online, the commonly used adhesives currently include PVDF, PTFE, SBR, LA133, etc. The bonding strength not only depends on the physical and chemical properties of the adhesive itself, but also on the surface characteristics of the copper foil. When the bonding strength of the coating is high enough, it can prevent the negative electrode from powdering and falling off during the charge discharge cycle, or the substrate from peeling off due to excessive expansion and contraction, thereby reducing the cycling capacity retention rate. On the contrary, if the bonding strength does not meet the requirements, as the number of cycles increases, the internal impedance of the battery will continue to increase due to the increased degree of coating peeling, and the decrease in cycling capacity will intensify.
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