Lithium battery termination tape

by:Yourijiu     2021-08-07
Lithium battery termination tape

Lithium battery termination tape, also known as special tape for lithium batteries, is a type of pressure-sensitive tape. It has certain acid and alkali resistance, high temperature resistance, solvent resistance, and electrolyte resistance. It mainly uses polyester film ( PET) or polypropylene film (PP) is the base material. The base material is coated with lithium battery electrolyte-resistant acrylic or rubber special glue, which is specially used for the insulation protection and fixing of the lithium battery cell termination and other parts.

1. Glue:

Rubber glue is basically no longer used because it contains easily oxidizable ingredients or halogen-based substances, and most of them use acrylic adhesives. Acrylic adhesives are synthesized by using different monomers or different proportions or different additives to form a variety of viscosity, various temperature resistance, various colors and many other types of termination tapes. The synthesis of acrylic glue is a chemical polymerization reaction, which is the process of polymerizing and crosslinking small molecules of the same or different compounds containing double bonds under specific conditions to form macromolecules. After the reaction, there is still part in the glue system. Monomer components and impurities exist, and some need to add a small amount of resin to adjust the viscosity. After the glue is synthesized, it is necessary to add color paste to make different colors before use, and add solvent to dilute it to make it suitable for tape coating. Therefore, the quality of the tape is closely related to the production of glue, and the unqualified glue is the main reason for the unqualified tape.

2. Substrate: The terminating tape mainly uses polyester film (PET) or polypropylene film (PP) as the substrate.

2.1 Polyethylene terephthalate is the most thermoplastic polyester The main variety is called Polythylene terephthalate in English, referred to as PET or PEIT (hereinafter referred to as PET), commonly known as polyester resin. It is a polycondensate of terephthalic acid and ethylene glycol with a density of 1.38. PET film is a more comprehensive packaging film. It has good mechanical properties, impact strength is 3 to 5 times that of pp, pvc film, and has good stiffness, good folding resistance, stable size, oil, fat, dilute acid, dilute alkali, and most solvents. It has excellent resistance to high and low temperatures. It can be used for more than 10 years in the temperature range of 120°C. It can withstand high temperatures of 150°C and low temperatures of -70°C in short-term use. The mechanical properties of high and low temperatures have little effect. However, it is not resistant to strong alkalis; it is easy to be charged with static electricity, and there is no proper anti-static method, so attention should be paid to it during use.

2.2 English name of polypropylene: Polypropylene, abbreviated as: PP, is a thermoplastic resin made by polymerization of propylene, with a density of 0.92. PP film has excellent moisture absorption, acid and alkali corrosion resistance, and solubility resistance. . However, it has no resistance to aromatic hydrocarbons (such as benzene) solvents, chlorinated hydrocarbons (carbon tetrachloride) solvents, etc., and still has low oxidation resistance at high temperatures. It has excellent electrical properties and can be used as a high-frequency insulating material. The temperature resistance of PP is not as good as pet, long-term temperature resistance is about 90℃, short-term use can withstand high temperature of 130℃, and low temperature of -50℃.

2.3 Comparison of pet tape and pp tape

The advantages of Pet are high impact resistance, high tensile strength, small heat shrinkage ratio, wide temperature resistance range, and can be used to make ultra-thin tapes with a thickness of less than 20 microns.

Pet's shortcomings are good strength, good folding resistance, stable size, and it is easy to cause the tape to be warped. The pressure-sensitive tape will wrap a small amount of air bubbles in the pole piece during the lamination process.

PP Advantages: Good flexibility, good processing performance, and it is not easy to cause the tape to be warped. The pressure-sensitive tape has fewer air bubbles during the lamination process and cannot be extracted from the pole piece.

Disadvantages of PP, low tensile strength, high temperature resistance The performance is poor, and the thickness of the tape is generally 30 microns or more.

3. The production of tape

The PP or PET film substrate is corona to obtain a film substrate with a rough side and a smooth side. Silicon release agent is coated to obtain a release film, and even a layer of digital ink and protective layer can be added to obtain a digital film. Then, the rough surface of these films is coated with special acrylic glue resistant to lithium battery electrolyte with curing agent. The glue is dried and cured by heating in the drying tunnel. Then cool and rewind according to specifications to obtain semi-finished products. The semi-finished products are then re-rolled, cut or slit to obtain the finished products, which can be packaged and sold. The equipment through which the tape is processed includes a tape coating machine, a precision rewinder, a precision slitting machine, and a precision slitting table. In order to ensure that the tape is not polluted during the production process, especially not polluted by magnetic substances, all processes are in the 10,000 level. The clean area is completed.

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