This article delves into the significance of polymer films in the construction of tabs for lithium-ion batteries. Specifically, we examine the role of a polymer film that is heat-sealed onto a metal substrate to form a functional tab. This film serves as both a bonding agent between the metal tab and the pouch film, encapsulating the contents of the pouch cell, and as an electrical insulator, preventing potential short-circuits between the tab and the aluminium pouch film.

Composition and Properties:

Typically, a polymer film comprises three distinct layers. The outer layers are specially modified to enhance adhesion to the metal substrate and the packaging pouch, featuring a lower melting point for effective sealing. The core layer acts as the structural backbone, binding the two outer layers together. Polypropylene-based polymers are commonly employed due to their exceptional chemical resistance and barrier properties. The film is available in transparent and grey variants, with the choice primarily influencing visual detection systems rather than core performance.

Critical Considerations:

When selecting a polymer film, thickness emerges as a vital parameter. Several factors come into play in this regard. Firstly, for a given material, the adhesion strength is directly proportional to the film’s thickness. Consequently, thicker polymer films are preferred for extended service life. Secondly, film thickness contributes to the overall tab thickness, which can impact pouch sealing, packaging, and welding processes. For instance, when cathode and anode tabs possess different thicknesses due to material properties, achieving consistent sealing on both tabs can be influenced by the tab thickness. Lastly, the metal’s shoulder represents a potential weak point, as pressing the tabs against the edges may cause the metal to pierce the polymer. While proper metal edge preparation can mitigate this issue, utilizing thxicker tapes against thicker metal can be advantageous, given the presence of a tapered edge that the tapes must overcome to form a complete edge seal.


The polymer tape assumes a vital role as an essential component in the construction of tabs, warranting careful attention and consideration. At Avocet Battery Materials, we possess the expertise and capability to conduct thorough research and manufacture tabs tailored to specific requirements. To learn more about our comprehensive range of products and services, and how we can assist you in your battery applications, please visit