From the abstract: A lithium-air battery based on lithium oxide (Li2O) formation can theoretically deliver an energy density that is comparable to that of gasoline.
This particular Li2O battery is a little under 700 Wh/kg, with the theoretical maximum being 11k Wh/kg, compared to gasoline's 13k Wh/kg. It's an incredible accomplishment that they have managed to get such a reaction reasonably stable. Minor improvements to the battery cited in the paper would be beyond the theoretical limits of existing commercial lithium chemistries.
> 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)
This statement about energy density is false, the result of an incorrect computation. The correct ideal energy density of lithium-air batteries is less than half of that of gasoline.
If it can be made small enough for use in mobile devices, I wonder whether the need for air/oxygen might require compromising on water-tightness. Would an oxygen permeable waterproof membrane allow enough through for operation? It would be interesting if instead of just for cooling, future high powered devices might also need a fan to feed the battery!
Not really. In a fuel cell the reaction products are discarded (the reactants cannot be discarded, as they are needed for the reaction to take place).
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).
I thought the problem with all of these metal air batteries is the sluggish oxygen reduction reaction at the air cathode. It just seems too slow for a high power density - need high surface area. The air cathode in this experiment is a gas diffusion layer embedded with trimolybdenum phosphide nanoparticle (seems common with these, others use platinum and iridium), with a current density of 0.1 mA/cm2. Need 1m2 of air cathode for 10 amps. I wonder how that ORR can be sped up or use smaller surface area. Could some kind of forced induction supercharger type thing work for these? I'm not a chemist.
Is there a way to determine how miles per kWh would change with different batteries in currently sold EVs? Would it be fair to say like half the weight but same energy content means double the distance per kWh
I'm a bit excited but also a bit tired of hearing about all these batteries. I just want someone to wake me up when we have a commercially available 1kwh+/kg with decent durability, decent price, and good safety.
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.
That feels like a very high bar. A really good 500Wh/kg battery would already be completely revolutionary. That’s when you start to unlock practical short range electric flights for instance. It’d probably be enough for all forms of land transportation as well (except very small niches, like if you need to cross a huge desert off-road)
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.
/Up to 1000 charge cycles/ is a big damper on the excitement, for me. Does anyone know if a limitation like that is inherent to the chemistry here or is this something that they could potentially (hopefully, vastly) surpass?
That's a comparable rating to the NMC Lithium cells used in an electric car, yet an EV can typically get > 200,000 miles from their cells. A charge cycle is defined as 0% -> 100% -> 0%. If you never do that, you get a lot more effective charge cycles.
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.
A study[1] was recently posted[2] which found that for lithium-ion batteries, dynamic use lead to much better battery life compared to fixed-current discharges which is typically used in labs to determine battery life.
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.
fs_tab|1 year ago
timerol|1 year ago
> 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)
adrian_b|1 year ago
See other comments for the correct computation.
shsudhdudi|1 year ago
Xamayon|1 year ago
fuzzfactor|1 year ago
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.
sroussey|1 year ago
aetherspawn|1 year ago
Would this technically make it a fuel cell and not a battery, since some of the reactants are discarded :)
adrian_b|1 year ago
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).
Drunk_Engineer|1 year ago
ralfd|1 year ago
Well. No. Not yet.
gnarcoregrizz|1 year ago
thehappypm|1 year ago
travisporter|1 year ago
sbensu|1 year ago
https://ouros.energy/
giantg2|1 year ago
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.
audunw|1 year ago
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.
hiddencost|1 year ago
Matterless|1 year ago
bryanlarsen|1 year ago
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.
magicalhippo|1 year ago
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.
[1]: https://www.nature.com/articles/s41560-024-01675-8
[2]: https://news.ycombinator.com/item?id=42370438
cyberax|1 year ago
numpad0|1 year ago