How long will it take to mass produce a practical-affordable version?

27Kwh/liter for the third chemistry? That is definitely worth exploring.

My second-gen Prius has a ~45 liter tank. Even if we take a more practical (say 15kwh/liter) real-life capacity, that would give a 675 kwh battery. With the electric consumption of the Prius (150 Wh/km) this would result in a 4500 km range.

Now, that would be a car that crushes all of the petrol-based competition.

@Engineer-Poet; Could not oxygen be fairly easily vented to the atmosphere using a diffuser and fan? I imagine that forced air blown into the area would quickly dilute the oxygen to non-hazardous levels. For a non-stationary application like automotive, those fans probably wouldn't need to be running very often.

These could be combined with SOFC/MCFC to do a V2G system. Heat, cool and power your home while having transportation when you need it with no imported oil.

Stationary applications might be better. The trick with SOFCs is not to thermally cycle them any more than you have to. You keep them running at temperature continuously, even at partial output.

It might still make a good CHCP system with an SOFC, the stack could be smaller then the battery would help with the high demand times. Either way this is a good bit of research.

You could compress the oxygen for later reuse, it would cut down on contaminants and extra moisture. I don't think fire danger would be a problem when properly mixed with the nitrogen in the air.

Could not oxygen be fairly easily vented to the atmosphere using a diffuser and fan?

Imagine oxygen building up to 30% or more in a space like a garage.  Now imagine someone walking into it with a lit cigarette, and dropping it on something flammable when it flares up in their face.  I wouldn't want to be near it.

Building codes for enclosed spaces with chargers may need to specify ventilation fans and sprinklers.  But they need this even more so for lead-acid battery banks, so the knowledge to do it right is already there.

@EP great points all around

Two things I'd like to add. First, with such a high potential specific energy, you can afford designs that reduce said specific energy by 20, 30, 50+% and you still end up with an incredibly dense energy source. Second, I get the feeling that this type of battery architecture would have a practically "unlimited" cycle capacity.

>>>>(i)"Recharging a 450 kWh to 675 kWh battery pack may take a while."(/i)

Why bother fast-charging a 450-kWh BEV? Why bother having a BEV with such a stupendous capacity at all?
An optimized, clean-sheet-design PHEV with a small 2-3-cylinder ICE of about 1 liter displacement, coupled with a small but reasonably-high-power-and-energy-density battery pack will be much more advantageous than a pure BEV having 100-450-kWh of super-energy-dense battery pack.

This is because a pure BEV will need fast-charging infrastructure to be built everywhere, yet is not often used, hence a very poor business model for this to takeoff. A PHEV takes advantage of existing fast energy fill-up at all existing gasoline stations, thus no new infrastructure investment.

Furthermore, for long trips through desolated areas, a PHEV can carry extra fuel in external tanks to cover distances as far as thousands of miles. A pure BEV will have problem with that.

A pure BEV will suffer from calendar life degradation of the battery pack before its cycle life can be used up. A PHEV can have a much smaller battery pack replaced several times during the life span of the car, thus is able to max out the battery's cycle life without significant calendar life degradation.

In another words, existing battery technology of 200Wh/kg Lithium battery is just fine and dandy for a very practical PHEV that can compete with ICEV in all aspects. Rapid adaptation of this existing battery technology to large-volume production will be far more practical than continue to wait for a silver-bullet battery solution like Li-air or solid-state battery...etc.

Existing engine and battery technology is sufficient to create a PHEV that is price competitive with existing ICEV as well as having comparable internal space and curb weight. The OEM's simply do not yet want to build such a PHEV!!!

I seem to recall that a V2O5 route was listed way back in the 60's as one of a handful of promising recyclable quasi-catalytic routes of producing hydrogen, as researched by Italian scientists. This was apparently a purely theoretical exercise as it was one of about 400 or so routes conjectured (You'd have to look it up in an old energy tech anthology edited by David Pimentel, which I do not have). It may be that something of this hot cell technology can be utilized to do just that. If so, the dangerous part of heating the process can be left to a protected central location, and you could just draw of the hydrogen for your cars instead. Water instead of air would be the source of oxygen and hydrogen.

This is similar to an iron smelting system reported on this blog that utilizes lithium carbonate and CO2, which has a lower free energy barrier than sci texts previously reported. Seems that the new Iron Age is upon us.

or the waste heat can be used for other purposes to improve the round-trip efficiency.

Our city has a number of district heating systems that put solar and industrial waste heat to use. I can see the waste heat from H2 electrolyzers and FC systems used likewise IF the temperatures are high enough.

Speaking of chewing away, my vehicle's lifetime average fuel economy surpassed 150 MPG today.  (It was close to that 3 weeks ago, but a 300-odd mile trip bumped it down to the low 130's and it's taken this much daily running on juice alone to run it back up.)

Still haven't put fuel in the car since June.

@Ralph,

Thanks for discussing this issue. Yes, the PHEV Ford Focus is renamed as C-Max Energi. It has a 4-cylinder-2-liter-144-hp engine. A 144-hp engine is desirable for the HEV version because the battery is rather weak. However, a PHEV has much more powerful battery to supplement the engine, so that only 72 hp, or 2 cylinders, would be desirable. Remember that the Prius gen II HEV has only ~72 hp from the 1.5-liter 1NZ-XFE engine and only 30 hp of battery power for supplemental power, and the Prius gen II has plenty of power for acceleration. The Prius gen III has around 33% more powerful engine and battery, yet does not feel any faster in acceleration when I drove both of them. Perhaps I used only a fraction of the power available for acceleration and therefore cannot appreciate the power different between the Prius gen II vs. the Prius gen III, yet I can keep up just fine with traffics in either version. This goes to show that hauling around dead weight of engine, drive train, motors, and battery is not a good idea for efficiency, nor for purchasing cost reduction.

The higher costs of HEV's and PHEV's have been barriers for more market penetration of those vehicles. The reduction in cargo space is another turn-off for PHEV's. By reducing the engine to 2 cylinder up front, some battery can be placed up front to reduce the loss of cargo space taken up by the battery pack behind the rear seat. Cost reduction is realized with downsized and simplified engine and motors. Furthermore, the fuel tank of the PHEV and HEV can be downsized to provide a range of only 300 miles instead of a range of 500-600 miles, thereby allowing more luggage space. The weight reduction from all of these can allow further weight reduction from the suspension and drive train and body and chassis in a clean sheet design, allowing a PHEV to have comparable weight and handling to a similar ICEV.

Please remember that the target audience for HEV and PHEV are not sport car enthusiasts desiring neck snapping acceleration, but efficiency-minded people who prefer to get around in a more gentle fashion.