Honda developed an aromatic electrolytic membrane, which offers outstanding hydrogen ion permeability, and a stamped metal separator, for superb electrical and thermal conductivity—a world's first in an automotive application. By improving electrical generating efficiency and through efforts to reduce stack size, the new stack has double the output and is half the size of its predecessor, achieving output density that ranks among the best in the world. What's more, this enables operation in temperatures from –20°C to +95°C, and enhances durability. Production and recycling are also easier. These breakthroughs herald a new generation in fuel cell performance.
Conventional stacks using carbon separators require independent seals, along with disk springs and backup plates held together with large bolts in order to maintain a tight seal. In comparison, the Honda FC Stack utilizes high-strength stamped metal separators that are 50% thinner than their carbon counterparts, and employs a unitized seal that results in an even thinner cell unit and fewer parts. What's more, the design takes advantage of the springiness of the metal separators to create a simple structure in which the stack is simply encased in panels, reducing the number of parts by half. The result is a fuel cell stack that is lighter and more compact, for a high-output, high-efficiency unit that achieves world-class output density (ratio of output to volume and weight) more than twice that of previous fuel cell stacks.
In order to maximize space efficiency in the fuel cell system box, the FCX uses two FC stacks that is made lighter and more compact through the use of stamped metal separators. The resulting layout freedom is utilized to enable a unitized construction for the humidifier module. Structural components is combined and other peripherals unitized to create a highly efficient layout for the system, achieving a more compact fuel cell system box.
The stamped metal separators can be formed using ordinary metal stamping technology and feature unitized seals, resulting in major savings in production time. This results in improved productivity. And because metal is used, the unit is also easier to recycle, further improving the FC Stack's prospects for future large-scale commercialization.