Extended Life from Fuel Cells for Phones

Japan's DoCoMo and Fujitsu Laboratories have developed a new and improved prototype methanol fuel cell for 3G FOMA handsets. The new prototype enables eight hours of continuous talk time, three times the capacity of the existing prototype, while weighing the same, 190g. The new device is expected to greatly extend usage time once it goes into commercial production.

DoCoMo improved the capacity by increasing the methanol concentration from 30% to over 99% and developing a method of recycling the generated water. DoCoMo unveiled a prototype micro fuel cell using methanol as an inexpensive source of fuel last September to meet user demands for more convenient handsets with greater power capacity and reduced environmental impact.

In addition to its work on micro fuel cells, DoCoMo is trying to increase the capacity of its lithium-ion batteries, the most commonly used battery in handsets today.

In comparison with conventional lithium ion batteries, micro fuel cells offer theoretical performance that is ten-fold, and are capable of high-density storage of energy at practical performance levels three times greater.

In addition, since micro fuel cells can use methanol derived from biomass resources, there is anticipation that they will help reduce environmental burden.

The performance of micro fuel cells depends on how compact they can be made and how much energy can be created from a given volume of fuel. Higher-capacity micro fuel cells will significantly improve user convenience, such as by increasing the number of times recharging is possible with a single cartridge.

Since micro fuel cells that employ methanol produce energy through the reaction between methanol and oxygen present in the air, power capacity can be increased by raising the concentration of the methanol solution. However, for passive type fuel cells that are suited for miniaturization and lighter weight, a phenomenon known as "methanol crossover" occurs, which is a fuel permeation that occurs between battery electrodes when high-concentration fuel is used directly with passive fuel cells, thereby resulting in lower generation efficiency.

Fujitsu developed new technology that makes it possible to use high-concentration methanol with concentration of over 99% for a passive micro fuel cell. By developing and employing a new material that reduces the methanol crossover effect by half compared to Fujitsu previous materials and to one-twentieth that of other commercially available materials, and by using the water by-product which appears during power generation to dilute the fuel, Fujitsu succeeded in effectively limiting the decline of power generation efficiency when using high-concentration fuel. Fujitsu and DoCoMo employed the new technology to co-develop an operable FOMA handset recharger prototype.

Using the newly developed technology, the cradle-type passive micro fuel cell achieved a world record high-power output average of approximately 1 watt with methanol fuel of over 99% concentration.

Fujitsu also verified that the prototype FOMA handset recharger using the micro fuel cell can charge up to three lithium ion power batteries embedded in a FOMA handset, with a single cartridge with 18 cc of methanol fuel.

In comparison to previous fuel cells from Fujitsu and DoCoMo which use methanolat 30% concentration, the prototype recharger using the new micro fuel cell enables up to three times the power output time with a single 18 cc methanol fuel cartridge.

Further work on the prototype, a cradle-shaped device, is expected to be completed by the end of March 2006."

Posted to the site on 7th July 2005