Fabrication and Electrical Characteristics of Graphite/Carbon Nanotube/Polyvinyl Butyral Composite Film via Tape-Casting and Heat-Treatment.

Composite stacking films, which can be applied as the bipolar plates of redox flow batteries, were fabricated via a tape-casting process that used slurry of graphite, CNT, and resin materials. The slurry was made of 25 similar to 45 wt% conductive filler (graphite, CNT) and 55 similar to 75 wt% polyvinyl butyral (PVB) binder solution (binder, dispersant, plasticizer, and solvent). The sheet thickness of the composite films was controlled to 70 similar to 150 mu m, and composite films of about 1 mm in thickness were also fabricated by stacking and laminating the sheet film, including the conductive filler of above 85 wt%. The effects of the shape and physical properties of the graphite were investigated with regard to the dispersion behavior and flow of the slurry on the carrier film of the tape-casting device. As a result, the acicular graphite showed a good dispersion property with the resin of the PVB binder, as compared to spherical graphite. The composite film with acicular graphite showed a lower resistivity than that of a film with spherical graphite. Furthermore, the effects of adding a small amount of CNT and the heat-treatment to the composite stacking film were also studied. Finally, the composite film showed an electrical characteristic of below 50 m Omega.cm and a high bending strength of above 20 MPa.