> The results shown in fig. S9 indicate that this solid-state Li-air battery cell can work up to a capacity of ~10.4 mAh/cm2, resulting in a specific energy of ~685 Wh/kgcell. In addition, the cell has a volumetric energy density of ~614 Wh/Lcell because it operates well in air with no deleterious effects (supplementary materials, section S6.3)
An 11 wh/kg battery would result in a battery that delivers about 5-6 times more miles per kg of battery than petrol. You get weight parity around 3-4 kg. If you factor in the weight of the engine (they can be quite heavy) it gets a little better. Of course the weight matters far less than people think. The amount of energy needed to move a vehicle does not necesseily scale linearly with weight of the vehicle. Which is why a heavy cyber truck and much lighter / smaller EVs can have miles per kwh metrics that aren't that far apart. Same with petrol cars. Halving the weight doesn't given them twice as much range. Heavy batteries are not that big of a deal. Unless you put them in a plane. Weight matters a lot in planes.
So, a battery like this would be amazing news for battery electric planes that currently fly with 200-300 wh/kg batteries (at best). 11kwh/kg would be a 70x improvement in energy density. That's a lot of range. Even a small fraction of that would be a massive improvement. 700wh/kg more than doubles the range already.
I think we'll see batteries break 1kwh/kg next decade or so. 500 wh/kg is already on its way to production. So, a doubling is only a modest step up. At 1kwh/kg, most GA flight will become electric. 3-6 hours of range with dirt cheap electricity turns a 100$ hamburger into a Starbucks coffee run. That's game over for ICE engines in small planes.
So to reach similar kWh/g we're looking at ~3k Wh/kg
A fuel cell with hydrocarbons would have a slightly better efficiency than the best mobile thermal engines, e.g. of 60%, while the ideal energy per mass ratio is more than double for hydrocarbons in comparison with lithium-air batteries, so even with a better efficiency lithium can never match hydrocarbons in usable energy per mass, not even in lithium-air batteries.
The claim from the parent article is wrong and it is based on an incorrect method for computing the ideal energy per mass ratio for lithium-air batteries.
The mass that must be used for computing the theoretical maximum is that of Li2O, not the mass of lithium. Per atom of lithium, the mass of Li2O is 2.14 times greater, so it is likely that the number quoted by you must be divided by 2.14.
Indeed, computing very approximately 1 electron x the value of the elementary charge x 3 volt x the number of Avogadro (per kmol) / 15 kilogram / 3600 seconds, gives about 5500 Wh/kg, so the value quoted by you is indeed wrong.
See other comments for the correct computation.
Or with a tank of pure oxygen, have the EV act like it was gasoline engine on nitrous oxide.
Somebody should calculate a ballpark figure for the number of grams or kilos of oxygen that would be needed per mile for an average vehicle.
No it won't. At most, the battery might need a small fan. Turbochargers are needed for regular cars because internal combustion engines just suck.
Would this technically make it a fuel cell and not a battery, since some of the reactants are discarded :)
In a metal-air battery, air from the atmosphere is taken into the battery and the oxygen from it becomes bound to the metal, in a metal oxide.
So unlike for a fuel cell, where the vehicle becomes lighter after the fuel is consumed and the reaction products are discarded, a metal-air battery becomes heavier when the metal fuel is spent, because the reaction product is stored inside the battery.
The metal-air battery becomes lighter again when it is charged and the oxygen stored inside it is released into the atmosphere.
A lithium-air battery can have a much better energy per mass than any other kind of lithium battery, but it cannot reach the energy per mass of hydrocarbons.
The reason is that for hydrocarbons the mass that counts is just the mass of the hydrocarbons, while for lithium-air batteries the mass that counts is not the mass of lithium, but the mass of the lithium oxide, i.e. the mass of the battery when it is mostly discharged.
A carbon atom from hydrocarbons can provide 6 electrons per atom, while a lithium atom provides only 1 electron per atom, albeit at a voltage more than 3 times greater than carbon atoms. The mass of a lithium atom is half of that of a CH2 group from hydrocarbons, so if the mass of lithium would have been the one that mattered, the ideal energy per mass would have been about the same for hydrocarbons and for lithium. However the additional mass in lithium oxide reduces the ideal energy per mass more than 2 times (when Li2O is the reaction product) or even 3 to 5 times (when peroxide or superoxide of lithium are the reaction products).
We currently call spent batteries "empty" but in this case spent = "full" (of oxygen).
I know that is decades out, of course.
In an aluminum-air battery vs. a lithium-air battery, the mass per electron is, in the most favorable case for lithium, of 17 for aluminum vs. 15 for lithium, which results in an energy per mass for aluminum of around 82% of that of lithium. However lithium forms by oxidation not only Li2O, but also peroxide Li2O2 and superoxide LiO2, which may worsen a lot the energy per mass.
In the parent article, they have succeeded to produce mostly Li2O, but even so their batteries have still produced some amounts of peroxide and superoxide during deep discharges.
So the energy per mass for aluminum-air batteries could be up to 80% to 85% of that of lithium-air batteries.
Most other oxidants besides the oxygen from air are heavier, which would reduce the advantage of lithium vs. aluminum (because the oxidant mass would be a greater fraction of the battery mass), so aluminum-ion batteries, if possible, could have an energy per mass very close to that of lithium-ion batteries.
On the other hand, aluminum metal and aluminum oxides are much denser than lithium metal and lithium oxides, so aluminum batteries could have much better energy per volume than lithium batteries. Unfortunately, until now the problems caused by aluminum as a cathode material have not been solved.
https://eepower.com/news/ev-with-1000-mile-range-unveiled-by... https://www.cbc.ca/news/science/electric-car-with-massive-ra...
Well. No. Not yet.
Maybe this is a good idea for an ammoseek website but for batteries that can send alerts. I'm honestly surprised a quick search didn't turn one up.
If you get to 1kwh/kg I don’t think you even need good durability and low price to have a revolutionary battery. At that energy density it could make economic sense to do medium range battery electric planes, even if you need to replace the battery every year. The operational costs related to using jet fuel (both fuel costs and engine maintenance) are huge. So the airplane industry can work with batteries that are more expensive and that requires more maintenance than what the EV market would accept.
I’m sure there’s a bunch of other niches for such a battery.
Edit:
That's not the full explanation. 300 miles of range for a typical EV * 1000 cycle rating gives 300,000 mile rating.
You likely charge a lot more than 1000 times over those 300,000 miles, but a partial charge counts as a partial cycle.
I don’t have exact numbers.. based on graphs I’ve seen I would guess that if the original cycle life was 1000 cycles you may have another 500 cycles until the battery is actually unusable. But it probably depends a lot on the specific chemistry and how the car is used.
From the paper: Specifically, for the same average current and voltage window, varying the dynamic discharge profile led to an increase of up to 38% in equivalent full cycles at end of life.
This tracks well with actual real-world data on BEV battery performance in cars with decent battery management.
