What is lithium battery tape? For batteries?

What is lithium battery tape?
Lithium battery tape refers to a pressure-sensitive adhesive tape used for electrode winding, pole piece protection and winding core termination in the middle production process of lithium battery cells (winding/stacking, shell welding and sealing processes). Its main function is to insulate and fix lithium batteries. The development of lithium battery tape is accompanied by the development of lithium-ion batteries.

Research status of lithium battery tape
Lithium battery tape is a pressure-sensitive tape with special functional characteristics. It has certain initial adhesion, sustained adhesion, temperature resistance and chemical corrosion resistance, and can be used repeatedly without pollution. After peeling, it does not pollute the surface of the adherend.
Lithium battery tape is divided into lithium battery tapes with different characteristics to meet customer and market needs due to different parts of lithium batteries, different functional requirements, different performance standards, etc.

The characteristics of lithium battery tape
It is mainly determined by factors such as substrate, adhesive and use, so lithium battery tape is generally classified according to substrate, adhesive and use.
There are many types of lithium battery tapes, all of which are developed and produced according to the customer’s requirements for the use of materials. Among them, the composition of the adhesive determines the characteristics and uses of the lithium battery tape. Commonly used adhesives include acrylic adhesives, rubber adhesives, etc.
Lithium battery tapes prepared using different adhesives as raw materials have different characteristics: acrylate lithium battery tapes prepared with acrylate adhesives have good aging resistance and weather resistance, high temperature resistance and good thermal stability, good adhesion to polar surfaces, low adhesion to non-polar surfaces, and low initial peel strength; rubber lithium battery tapes prepared with rubber adhesives have higher shear resistance at high temperatures, can be pasted to various surfaces, and have good initial adhesion, but poor aging resistance and solvent resistance.

Preparation of lithium battery tape
Different lithium batteries use different lithium battery tapes due to their different battery types, models and production equipment. In general, the preparation and application process of lithium battery tape is as follows:
①Substrate treatment: PP, PET and PI film substrates are subjected to surface corona treatment to obtain a film substrate with one side rough and the other side smooth. Release agents can also be applied to the non-glue surface to obtain a release film, or a layer of digital ink can be added to obtain a digital film;
②Gluing: Apply pressure-sensitive glue on the corona surface of the treated film, and dry and solidify the glue through a high-temperature drying tunnel;
③Reeling: Cool the equipment and reel according to the specifications to obtain a semi-finished product;
④Cutting: When the semi-finished product is rolled, the mother roll is rewound and then slit or stripped to obtain the finished product (when the semi-finished product is rolled, only small rolls are collected, which can be directly slit or stripped to obtain the finished product) and can be packaged and sold.
The equipment used for processing tapes include tape coating machines, precision rewinding machines, precision slitting machines, and precision slitting machines. In order to ensure that the tape is not contaminated during the production process, especially by magnetic substances, all processes must be completed in a clean area above Class 10,000.

Substrate of lithium battery tape
The substrate is the carrier in the lithium battery tape, which affects the temperature range, tensile strength, shear resistance and material cost of the lithium battery tape.

Common substrates include BOPP (biaxially oriented polypropylene film), PET (high temperature resistant polyester film), PI (polyimide film) and nomex (meta-aramid or aramid 1313) paper; polymer film has become a common carrier substrate for lithium battery tapes due to its excellent properties such as dimensional stability, high elasticity, good insulation, good acid and alkali resistance, good tear strength and resistance to plasticizers.
Different substrates give lithium battery tapes different characteristics. Guo Peijun et al. added appropriate amounts of crosslinking agents and pigments to the same acrylic glue to make BOPP and PET substrate adhesive tapes respectively. The products with BOPP film as the substrate have poor heat resistance and electrolyte resistance compared to PET-based tapes.
The heat resistance of the substrate determines the upper limit of the use temperature environment of the lithium battery tape. In terms of heat resistance, PI substrate>PET substrate>BOPP substrate, PI substrate has the best heat resistance, and BOPP substrate has the worst heat resistance.
The cost of the substrate is opposite to the heat resistance. The cost of BOPP lithium battery tape is relatively the lowest, and the cost of PI lithium battery tape is relatively the highest.
Hot-melt lithium battery tape

With the development of new materials, the lithium battery tape industry has introduced some new types of adhesives, such as single-sided hot-melt lithium battery tape and double-sided hot-melt tape for lithium batteries.
The single-sided hot-melt lithium battery tape is composed of a sealed hot-melt pressure-sensitive adhesive layer and a base film layer. The single-sided tape has good viscosity, can resist the corrosion of the electrolyte of the lithium battery, does not react chemically with the electrolyte in the lithium battery, and maintains the performance of the lithium battery.
The lithium battery pole group and the outer packaging material using the single-sided hot-melt lithium battery tape are firmly bonded, and there will be no relative displacement. It has good anti-fall ability, high safety, long service life and stable quality.
One side of the double-sided tape for lithium batteries is sticky, usually acrylic glue; the other side is non-sticky at room temperature, and becomes sticky when heated, usually hot melt glue.
During use, one side of the tape has adhesion to aluminum foil and polyethylene film at room temperature, and the other side will have adhesion to the polypropylene surface only in an environment above 80°C, which is more suitable for the production process requirements of lithium batteries.

Lithium battery termination tape
Lithium battery termination tape refers to a pressure-sensitive adhesive tape used for electrode winding and core termination in the winding/stacking process of the lithium battery cell mid-stage production process. In addition to the general properties of pressure-sensitive tapes, this tape also has special requirements in terms of substrate selection, adhesion, temperature resistance and electrolyte resistance. It is a special type of pressure-sensitive adhesive product.
Lithium battery termination tape is a type of pressure-sensitive tape that is widely used in batteries.
Using monomers such as isooctyl acrylate, butyl acrylate, acrylic acid and vinyl acetate as raw materials, adding initiators and using solution polymerization to successfully prepare an acrylic pressure-sensitive adhesive with an initial adhesion of 9# steel ball, a peel strength of 8.3~8.5N/25 mm, and a sustained adhesion of 299min. Its performance meets the requirements of lithium battery production process.

Lithium battery high temperature tape
Lithium battery high temperature tape is developed to make lithium batteries have good stability under extreme high temperature conditions such as production and use. It is required that lithium batteries can maintain structural stability and chemical properties for a long time in high temperature environments, and ensure that lithium batteries do not short-circuit, leak electricity, or leak liquid in high temperature environments.
The original lithium battery high temperature tape was silicone tape, but in recent years, the lithium battery industry has proposed that silicon should not be contained in the battery cell, so most of the high temperature tapes used on the market are acrylic battery tapes.

Lithium battery tab tape
When making lithium battery cells, it is necessary to weld Tab lead (TAB lead) on the tab, so that the tab is lengthened, which is convenient for the next process to melt the sealant for sealing when the top side is sealed. Tab lead welding uses ultrasonic welding. After welding, there will be welding spots on the tab.
Because the height position of the tab extension may not meet the requirements. Generally, the tab needs to be bent, which is prone to short circuit, so it is necessary to add insulating tape to the welding position, and both sides of the tab need to be pasted with insulating tape.
Double-layer lithium battery protective film tape
The lithium battery shell is hard and has sharp corners. The lithium battery tape for protecting the edge is required to be soft, sticky, good in adhesion, and not warping for a long time. This type of tape is called double-layer lithium battery protective film tape.
The composite structure of double-layer PET film and double-layer adhesive layer makes the tape softer while being wear-resistant and tough; by coating high-viscosity modified acrylic adhesive with phenolic resin, the adhesive is stronger, so that the tape has better adhesion and is not easy to warp, and it can be baked at 130℃ for more than 0.5 without residual glue when torn off, which can better protect the battery.

Power battery tape
The power battery tape is a battery tape that uses PET film as the base material and is coated with non-silicon pressure-sensitive adhesive (acrylate glue or rubber glue) on the PET film. It is used for the shell of the soft-package power battery of electric vehicles, the battery cell set in the shell, the top cover of the cover shell, the top surface of the battery cell, the two sides and the bottom surface.
Lithium battery protective film Lithium battery protective film tape mainly uses PET film and BOPP film as the base material, coated with acrylic glue, and is used for the bonding and protection of the aluminum-plastic film surface during the production of soft-pack batteries and polymer lithium batteries.
The characteristics are high cleanliness, moderate viscosity, no warping when pasting aluminum-plastic film, no damage to barcode, resistance to certain high temperatures without residual glue, scratch resistance, puncture resistance, and products meet ROHS standards.