kuraray


News Releases 2006

Development of an Eco- Friendly Electrolyte Membrane Through a New Carbon Hydride Derived Polymer
~Significant Increase in Fuel Cell Performance~

January 24, 2006
Kuraray Co., Ltd.

Kuraray has developed a new electrolyte membrane for use in methanol-based fuel cells (Direct Methanol Fuel Cells / DMFCs)*1, based upon technology related to a high-performance carbon hydride derived polymer. Compared with conventional fluorine-derived electrolyte membranes, the newly developed carbon hydride-derived electrolyte membranes reduce methanol permeability (methanol crossover)*2 during power generation by 40%, boosting maximum power output by 1.6 times.

The market for DMFCs for mobile devices is projected to undergo full-fledged growth in the near future. Contributing factors include the launch of digital broadcasting via mobile devices from April 2006, and the relaxation of regulations that govern the carrying of methanol cartridges onto airplanes, scheduled for January 2007.

Until now, fluorine-derived electrolyte membranes used in hydrogen-based fuel cells had been difficult to make practical use of in DMFCs. This was due to the fact that, while hydrogen ions easily passed through the membranes, methanol also easily passed through, leading to decreased performance and fuel loss. Though many companies are currently battling fiercely to develop engineering plastic and other new carbon hydride-derived electrolyte membranes that inhibit methanol crossover, those companies are facing a technological hurdle. Engineers have found that efficient passage of hydrogen ions is always sacrificed when methanol crossover is inhibited, and therefore have been unable to increase output performance.

Using its proprietary elastomers and unique membrane production technology, Kuraray solved these problems by controlling the membrane's nanostructure, and succeeded in significantly boosting power generating performance. The membranes developed by Kuraray are especially superior when solutions of high methanol concentration are used as fuels, enabling use of smaller fuel tanks and contributing to more compact battery sizes. Further merits are gained due to the flexible nature of the elastomer extract, which adheres closely to electrodes to enhance power generating performance and ease of assembly.

Kuraray aims to commercialize the electrolyte membranes during 2008. While advancing with the development of electrolyte membranes for DMFCs and membrane/electrode assemblies (MEAs)*3, Kuraray will also pursue the development of polymer electrolyte membranes for use in automotive and home use hydrogen-based fuel cells, as environmental considerations call for halogen-free technologies.

The newly developed electrolyte membranes and MEAs will be introduced at the 2nd International Hydrogen & Fuel Cell Expo, to be held at Tokyo Big Sight from Wednesday, January 25 through Friday, January 27, 2006.

Characteristics of Kuraray's Newly Developed Membranes
  Kuraray-developed membrane Fluorine-derived Engineering plastic-derived Notes
Efficient passage of Hydrogen ions Most important capability
Reduced methanol crossover - In DMFCs, must also allow easy passage of hydrogen ions
Flexibility Linked with good adhesion to catalysts and to ease of assembly
Mechanical durability Few changes to dimensions in methanol and water. Flexibility prevents easy breakage
Chemical durability Same level as fluorine-derived
Halogen-free Yes No Yes Eco-Friendly
◎ Excellent
Good
Fair
Poor

Explanation of Terms

*1 Direct Methanol Fuel Cell (DMFC)
Within the category of polymer electrolyte fuel cells (PEFCs), a DMFC is one that utilizes methanol for fuel. Anticipated as a next-generation power source for mobile devices based upon their ability to perform at low temperatures, their high theoretical energy density in comparison with gaseous fuels, and their compact nature that comes from the fact that fuel modification is unnecessary.
*2 Methanol Crossover
The phenomenon of methanol supplied from the anode (electrode from which electrons flow out) side permeating the polymer electrolyte membrane and reacting on the cathode (electrode into which electrons flow) side. Methanol that reacts on the cathode side not only generates heat and causes fuel loss, but is also linked with reduced power generating performance due to sub-reactions. It is generally known that suppressing methanol crossover in electrolyte membranes is related to a decrease in the conductivity of hydrogen ions.
*3 Membrane Electrode Assembly (MEA)
A primary component responsible for power generation, consisting of an electrode joined to both sides of an electrolyte membrane. The electrode supports a catalyst through use of a binder attached to carbon paper or other material.