The pouch cell tabs are compounded by heat adhesive film and metal strips.

The heat adhesive film of pouch cell tabs is usually composed of three layers of materials by hot pressing together, including a middle framework layer and two surface modified PP layers, and the modified PP materials on the two surfaces are the same.

Of course, there are some exceptions. For example, the single-layer modified PP composition produced by Toppan and Showa and the five-layer tab heat adhesive produced by ZACROS.

For another example, in order to pursue ultra-high bonding strength between the adhesive layer and the metal tape, Hitachi and ZACROS have different modified PP materials on the two surfaces. One side is metal-philic modified PP, and the other surface is plastic-philic modified PP. This kind of heat adhesive, once the surface of the heat adhesive is reversed when making the pouch cell tabs, it will inevitably cause the battery cell to leak and swell.

1) Pouch cell tabs with black heat adhesive VS Pouch cell tabs with yellow heat adhesive

1.1) Pouch cell tabs with black heat adhesive

DNP's pouch cell tabs with black heat adhesive are composed of PEN functional layer and PPa layer. There are many interfaces between different substances, and it will peel off after being soaked in electrolyte.

The PEN functional layer has a melting point of 265°C, and the PPa layer has a melting point of 147°C. And there are 3 kinds of substances with different melting points in the PPa layer, melanin: 66℃, PE: 105℃, PP: 167℃, the interfaces are more unstable.

1.2) Pouch cell tabs with yellow heat adhesive

The melting point of the yellow heat adhesive functional layer itself is above 300℃, so it will be better to operate during heat sealing.

The PEN functional layer in the middle uses a non-woven fiber layer instead of the original polyethylene naphthalate. The interface fusion is better than black heat adhesive, but it still cannot solve the problem of complete fusion between different substances.

Due to its own PPa layer technology, yellow heat adhesive will become extremely hard and lose flexibility after heat sealing. It is easy to cause the tab heat adhesive and tab metal to break when the battery is packaged and later processing (transferring nickel, adding plates). As a result, the battery leaks, swells, and so on.

2) Pouch cell tabs with yellow heat adhesive VS Pouch cell tabs with white heat adhesive

The white heat adhesive is co-extruded by three layers of PP materials with different functions. The heat-sealing temperature of the functional layer is 165~167℃, which is slightly lower than the battery packaging temperature (180~220℃), which can effectively prevent the short-circuit problem of the section. The operating temperature range during battery packaging is increased, and the yield rate of battery production is improved.

Since the materials used in the 3 functional layers belong to the same kind of material (PP), the white heat adhesive can still maintain extremely high flexibility after heat sealing.

3) Pouch cell tabs with single-layer white heat adhesive VS Pouch cell tabs with three-layer white heat adhesive

Single-layer white heat adhesive has only one melting point. If the heat-sealing temperature exceeds the melting point, it will easily lead to complete melting and short circuit. When the heat-sealing temperature is insufficient, it will soften, which will cause the CPP layer of the aluminum laminate film to not completely melt and polymerize, and the battery is easy to leak and swell.

The outer layer of the three-layer white heat adhesive is made of similar materials to the inner layer of the aluminum laminate film, which ensures the fusion with the aluminum laminate film. In addition, the temperature difference of more than 30°C between the surface modified PP and the intermediate layer PP has a wider heat-sealing temperature, which makes the operability of the package stronger, and ensures the reliability of the package between the heat adhesive and the aluminum laminate film.

WinAck Group can provide various types of pouch cell tabs with customizable sizes. Come by, contact us for a solution that can help you succeed. For better batteries, Win & Ack!