PVDF Electrode Binders & Separator Coatings

Not All Resins are Equal

For a couple of decades now, PVDF resins have proven themselves to be the best choice for highly stable electrode binder resins – particularly for the cathode. The choice of PVDF binder and separator coating resin is driven by two main factors:

• Proof of extreme performance under extreme conditions 
• Peace of mind – assurance of global supply, quality, compliance, and commitment to ongoing development for the next generation of batter

By nature, Kynar^® PVDF is designed for extreme environments. The best evidence of this is the multiple outstanding track records of uses such as high durability skyscraper coatings (more than 50 years), subsea pipes for Oil and Gas (more than 26 years) and photovoltaic panel protection (more than 10 years). As one of the pioneers in the evolving battery market, Arkema has quickly grown through intense innovation to its position today as a global reference and a leading supplier of high quality resins.

Tailor-Made Performance

Arkema has been a pioneer in the development of high performance PVDF resins and flexible copolymers for several decades. Our proprietary process allows careful tailoring of molecular weight, particle size, crystallinity, and functionality.

Emulsion PVDF was originally designed, more than 50 years ago for high-end construction coatings where a small particle size is required to get a high level of gloss and smooth surface finish.

Higher Surface Area = Easier Dissolution = Faster Processing.

Today, in battery applications, those small particles, combined with their unique aggregated structure, result in a fast dissolution rate into NMP or Acetone as opposed to large suspension particles where NMP diffusion into the beads may be extremely slow. The small particles are also key in enabling a revolutionary ‘dry process mixing’.

Higher Level of Inversion

Emulsion polymerization can induce a higher level of head-to-head ‘defects’. This phenomenon is simply related to higher reaction temperature and can be seen in a slightly lower melting point and crystallinity versus suspension PVDF homopolymers.  Inversion ‘defects’ actually increase the alkaline resistance of PVDF which is critical when using high Nickel NMC active materials.

For the sake of clarity, it is interesting to understand that playing on polymerization temperature using the emulsion process allows for the tuning or tailoring of the ‘defect’ level.

Molecular Weight Polydispersity

While Kynar^® PVDF emulsion polymerization typically produces a mono-modal distribution of molecular weight,  it also offers flexibility to synthesize grades with a tailored bi-modal and/or broad polydispersity, providing unique solutions to certain demanding applications.

Depending on the manufacturing process, it may be desirable to synthesize grades with a tailored polydispersity index, providing unique solutions to certain demanding applications. This ability to tailor the molecular weight distribution is a key benefit of Arkema’s process.