Teijin Limited has developed a gas-diffusion layer (GDL) with a thickness of just 50 micrometers, the industry’s thinnest level, by combining the company’s ultra-fine fibrous carbon and para-aramid fiber using proprietary papermaking technology. Teijin expects its new GDL to contribute to the realization of smaller, more functional and lower cost fuel cells, the demand for which is expanding.

The GDL is a component used inside a fuel cell to supply H₂ and oxygen, collect electrons generated by the chemical reaction of the electrodes, and drain water generated in the process. The GDL's microporous structure incorporates Teijin’s PotenCia fine carbon fiber and Twaron para-aramid fiber, which are combined in a manufacturing process that has been sped up by deploying proprietary paper-making technology.

PotenCia enables the new GDL to achieve excellent conductivity without damaging the catalyst layer inside the fuel cell while Twaron contributes to high durability and water repellency. As a result, a conventional microporous layer (MPL) is not required, allowing the new GDL to be slimmed down to 50 micrometers, which is less than half the thickness of a conventional GDL. The new GDL is also expected to reduce production costs by shortening the manufacturing process as well as reducing the number of raw materials required.

Teijin is now verifying the GDL's gas diffusion and thermal conductivity, both indispensable for high performance, and also its contribution to reduced environmental impact. Concurrently, Teijin plans to develop new materials that could use the GDL, such as electrode films, in partnership with other companies that share Teijin's vision for achieving smaller and more functional fuel cells.

Teijin leveraged its extensive experience with fiber-processing technology to develop PotenCia, an ultrafine fibrous carbon featuring long fibers and high crystallinity. To take advantage of the carbon's thermal conductivity and other special properties, Teijin 50μm Cross section of Teijin’s new GDL Manufacturing conventional GDL (above) and new GDL focused on the possibility to realizing an extra-thin GDL for fuel cells.

GDLs usually comprise a conductive fiber sheet made of durable carbon, which is combined with a water-repellent MPL that prevents the accumulation of water but increases the GDL's thickness, thereby lowering the fuel cell's power performance while adding to the manufacturing cost.