PVDF Separator Coatings | Arkema High Performance Polymers

The PVDF separator coating is a key driver in adhesive-type separators for the cell assembly process and cell performance. The cell assembly process has been evolving continuously and new trends are emerging. For instance, lines go faster targeting zero defects, stacking process is gaining more share over the winding process in prismatic cells ...
In a porous separator, the adhesive layer ensures the alignment between the electrodes and the separator during cell assembly. On the cell performance side, the adhesive layer helps to prevent cell deformation and improves the stability of the electrode/separator interfaces leading to durable charging cycle performance.

Unmatched performance of PVDF for battery separator coatings

Why select PVDF for battery separator coatings ?

Not so many materials are being used to develop this adhesiveness as the technical requirements are extremelly challenging.

Benefits of using PVDF as adhesive layer for battery separator coatings:

Improved cell manufacturing: adjusted dry adhesion between the separator and electrodes allowing a perfect alignment during manufacturing, better electrolyte wettability vs polyolefin
Improved cycling performances: excellent wet adhesion preventing cell deformation (no interfacial debonding)
Improved safety: better thermal dimensional stability, especially when combined with ceramics

Separator coating with Kynar® PVDF

The coating remains porous thanks to the fine particle size of Kynar® PVDF

Today, PVDF stands out as the optimal material for the adhesive layer of separators, combining dry and wet adhesion without comprimising resistivity.

The main advantage of PVDF versus most other coating chemistries for adhesive layers is the limited and controlled swelling when exposed to electrolytes. This prevents the undesirable clogging of the separator's pores, maintaining the low resistivity and the overall performance of the cell.

Performance advantages of Emulsion PVDF over Suspension PVDF for battery separator coatings

Not all PVDF polymers are made the same way: Arkema produces its Kynar® PVDF grades by emulsion process and without the use of fluorosurfactants.

Suspension PVDF can only be used in old fashioned solvent born process. On the contrary, thanks to highly controlled primary and secondary particle size, Emulsion PVDF is the only solution for waterborne technologies.

Comparison of the particle size for battery separator coatings, showing that emulsion PVDF performs better than suspension PVDF in waterborne process

A unique offering and expertise in waterborne coating technologies

Thanks to its emulsion process, Arkema is able to offer Kynar® PVDF solutions in both Latex and Powder forms.

Kynar® PVDF ranges for battery separator coatings provide great electrode adhesion in both wet & dry conditions, high voltage stability, high dimensional stability, controlled crystallinity and ceramic compatibility.

KYNAR® PVDF AQUEOUS LATEX

Aqueous media in which the primary PVDF particles remain dispersed. Typically preferred in microgravure process.

$Kynar PVDF Latex for battery separator coatings$

Benefiting from Arkema's extensive legacy expertise in water-based coatings, Kynar® PVDF latexes are designed for an optimal performance in coating applications combined with an outstanding shelf life and stability.

KYNAR® PVDF POWDER

Powder to be redispersed in an aqueous phase. Typically preferred in microgravure and spray coating processes.

Kynar PVDF powder for battery separator coatings

The powder is derived from an initial latex that undergoes a drying process. During this process, primary particles agglomerate to create small secondary particles. Arkema has acquired a significant level of expertise in precisely managing the size of this powder.

Recognizing that each battery manufacturer uses a unique electrolyte formulation, the demand for customized solutions requires copolymers with precise swelling characteristics. In addition to offering both powders and latexes, Arkema provides the widest portfolio of KynarFlex® copolymers to fulfill the various technical needs of customers.

FOCUS ON: KYNAR® PVDF POWDERS

This powder redispersion technique is used typically in spray coating or microgravure processes. In that case, the Kynar® PVDF powder is dispersed into an aqueous media followed by a milling step to achieve the desired particle size. The slurry is then post formulated.

Possibility to adjust the particle size distribution from 7 to 1 µm by varying the grinding parameters (grinding time, bead size, filling ratio, rpm, …)

A unique R&D expertise in battery materials

Center of Excellence for Batteries

Arkema's Christian Collette Center of Excellence for Batteries (located in Pierre-benite, France) is dedicated to new development programs in line with next-generation battery technologies. Equipped with state-of-the-art equipment, the R&D teams have advanced coating, assembly and testing capabilities to support your battery separator developments.

REACH OUT TO A BATTERY EXPERT