Fuel Cell Electric Vehicles are currently the most promising 300+-mile range, quick refill, petroleum/emissions-free option. If you want all of those elements, this is the best option we see. We don’t see Li-ion, Li-air getting us to this point.

—Mark Mathias

Mathias, who has worked on materials R&D for both batteries and fuel cells, spent a bit of time talking about the difference in the different way the two technologies scale with energy.

You need about 100 kWh at the wheel to drive about 300 miles. If you want the 100 kWh with a battery, the only way to do it is to add more battery. In a fuel cell system, even if you don't drive a single mile, you need the fuel cell system and the battery, and then to get range you put on hydrogen—this is analogous to what we do with the internal combustion engine today.

Those scaling factors dictate the way the energy density turns out for the two systems.

—Mark Mathias

Energy density and scaling of fuel cell and battery systems. Top row: Gravimetric and volumetric energy and range (required energy). Bottom row: System mass vs. vehicle range. Battery and fuel cell system scale very differently with range; batteries favor low range, fuel cells favor high, Mathias said. Source: Mathias, SAE HEVT 2014; Wagner et al. (2010). Click to enlarge.

GM and Honda. GM and Honda have cross-licensed their intellectual property and know-how as part of the partnership deal. “This is a great business deal because there is no question we ask them they can’t answer and vice versa,” said Mathias. Honda plans to go more broadly to market in the 2015 time frame with a fuel cell vehicle; GM has yet to announce plans to go to market.

We are working on fuel cell conversion and hydrogen storage technology; multiple generations, our current focus is 2020, but the intent will be to go beyond that. The big thing is we want to use common component system design to achieve economies of scale.

—Mark Mathias

Mathias noted that Honda and GM had taken different approaches; in the FCX Clarity, Honda packages the stack (with a vertical flow) between the passengers (earlier post) as opposed to under the hood.

All of this is on the table with regard to what we do in 2020...many of the things we are doing is the same. Physics is physics.

—Mark Mathias

System components for a fuel cell vehicle. Click to enlarge.

Stack materials, designs and processes are the key cost reduction areas; about 45% of the cost of the fuel cell system is in the stack. Major priorities for cost reduction are the electrodes (i.e., the cost of the Pt catalyst); bipolar plates, and membranes. Those three elements constitute roughly 80% of the stack cost.

All the OEMs over the last decade that are serious about this business own the design of the cell. The plate designs, integrating these materials, we don’t necessarily make membranes and catalysts, but it was going too slow the other way when we had one guy trying to provide MEAs [membrane electrode assembly] to everybody, it was just going way too slow. The OEMS realized that this is where the meat and potatoes of this thing is, you need to focus on that and get it aligned with your system because the interactions are extreme. So what we do is buy fundamental materials and integrate them into an MEA.

—Mark Mathias

In terms of platinum reduction, Mathias noted that there are some lower-cost platinum alloys that have exhibited targeted activity at the beginning of life—but that durability remains an issue to be solved. Durability challenges remain for all the materials with which they have worked, except for pure platinum nanoparticles.

One needs to learn how to make this stuff stable. There is work at the material level and the system level to get that done.

—Mark Mathias

Also at the SAE event, engineers from Hyundai and Toyota gave talks on their fuel cell vehicles coming to market in the next few years.

Resources

• Frederick T. Wagner, Balasubramanian Lakshmanan, and Mark F. Mathias (2010) “Electrochemistry and the Future of the Automobile,” The Journal of Physical Chemistry Letters 1 (14), 2204-2219 doi: 10.1021/jz100553m