Heat resistant coating binder "PNVA" <GE191 Series>

Separator is one of key components in Li-ion battery（LIB）. It isolates the cathode and anode, and plays an important role in the safety of LIB. Resonac offers Poly N-vinylacetamide ("PNVA") <GE191 series>, an original water-soluble polymer as binder for separator coatings. "PNVA" exhibits excellent thermal stability and high coating property. Separator coated with ceramic particles and "PNVA" contributes to enhancing safety and energy density of LIB.

What is "PNVA"？

"PNVA" is the water-soluble polymer produced by polymerization of N-vinylacetamide. Resonac only succeeded in the commercial production.

Resonac has started sales of "PNVA" in 1997, and it has been used for the application such as flocculants, poultice bases, water absorption rubber and so on.

"PNVA" <GE191 series> is　suitable for the binders of the ceramic heat resistance layers for LIB separator and electrode. Owing to higher number of hydrogen bond structure, it enables more uniform dispersion of metal oxide particles and thinner coating layer. These characteristics contribute to increasing energy density and reducing production cost.

Because "PNVA" enhances heat resistance of coating layer, it improves safety and durability of LIBs, "PNVA" <GE191 series> has already been employed for LIB of xEVs.

Basic properties

• Excellent heat resistance
• High dispersing performance and excellent thixotropy (Storage stability, high speed coating, thinner ceramic coating)

High heat resistance of the ceramic heat resistance layer

Generally, LIB separators are composed of films of polyethylene or polypropylene, which contain crystals with a melting point of around 130-150 degrees Celsius. When the temperature keeps increasing, the crystals of the separator completely fuse below 200 degrees and the separator film contracts. Then, this may causes ignition triggered by the contact of the electrode materials and consequential short-circuits. The addition of the "PNVA" <GE191 series> prevents contact of anode/cathode and contributes to safety enhancement. The shape of the heat-resistant layer of separators is maintained by adding "PNVA" <GE191 series>, which enables to avoid possible short-circuit and ignition while adding PVP or CMC-Na does not contribute to such result.

Heat Resistance Test

Cost reduction and high energy density with uniform thin coating

"PNVA" <GE191 series> shows high hydrophilicity. In aqueous solution, the　molecular chains spread and　viscosity of the water solution largely increases. Also, it is possible to form homogeneous dispersion of ceramic particle and it has a good thixotropy. Hence, the viscosity is　well reduced in accordance with shear rate.

Homogeneity of the dispersion is kept for long period of time. Hence, it is able to reduce material loss and prepare thin and smooth ceramic coating layer at high rate. Due to these characteristics, "PNVA" GE191 is able to contribute to process cost reduction and energy density increase.

Coating properties

Because viscosity of coating material with "PNVA" decreases under higher share rate condition, it is possible to prepare homogeneous coating layer even at a high speed.

• ※"PNVA" is a registered trademark of Resonac Corporation in the European Union, China, and Japan.