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Stabilization of gamma sulfur at room temperature to use in Li-S batteries

nature.com

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Re: Stabilization of gamma sulfur at room temperature to use in Li-S batteries

#21

Post by jojobas »

mjevans wrote: post #9
jojobas wrote: post #6

So they are claiming 800 mA-h per gram, which at 2.5V Li-S voltage gives about 7.2 megajoules per kilo, 1.5 the energy density of TNT. Somehow I don't want to be anywhere near a battery with that kind of energy density.

A quick search on Google: petrol megajoules Petrol/gasoline 44-46 MJ/kg Diesel fuel 42-46 MJ/kg Crude oil 42-47 MJ/kg You're already near far denser volatile chemicals, even if it isn't you driving someone else is somewhere.

Gas/diesel/whatever have energy density of zero. If somebody were to make petrol/oxygen stoichiometric soda, damn right I wouldn't want to be near it either.

Re: Stabilization of gamma sulfur at room temperature to use in Li-S batteries

#22

Post by jojobas »

thehappypm wrote: post #17
jojobas wrote: post #6

So they are claiming 800 mA-h per gram, which at 2.5V Li-S voltage gives about 7.2 megajoules per kilo, 1.5 the energy density of TNT. Somehow I don't want to be anywhere near a battery with that kind of energy density.

TNT is much more about power than energy. Releasing a megajoule in a tiny fraction of a second is far more destructive than burning a quart of gasoline in a bucket.

Power output of petrol in a bucket is limited by air supply. Batteries have all components for runaway energy release right there.

Re: Stabilization of gamma sulfur at room temperature to use in Li-S batteries

#23

Post by Klinky »

Schroedingersat wrote: post #20
Klinky wrote: post #19

Earlier quoted context omitted.

How are you calculating the volumetric energy density and the energy content of a liter of gasoline? 12kJ/L seems low.

In the context of comparing it to TnT or a Sulfur battery you need the oxygen too.

Perhaps I am misunderstanding, but that sounds almost like a calculation that applies to a vacuum, not a pressurized atmosphere with plenty of "free" oxygen? Perhaps that's the same for the TNT & battery, so maybe none of these calculations are directly applicable to real-world scenarios?

Re: Stabilization of gamma sulfur at room temperature to use in Li-S batteries

#24

Post by Schroedingersat »

Klinky wrote: post #23
Schroedingersat wrote: post #20

Earlier quoted context omitted.

In the context of comparing it to TnT or a Sulfur battery you need the oxygen too.

Perhaps I am misunderstanding, but that sounds almost like a calculation that applies to a vacuum, not a pressurized atmosphere with plenty of "free" oxygen? Perhaps that's the same for the TNT & battery, so maybe none of these calculations are directly applicable to real-world scenarios?

The point is the kg of hydrocarbon is less able to release its 40MJ all at once because the oxygen which is spread out over 4000 times as much volume needs to get to it. The battery contains both ends of the reaction, but the hydrocarbon only contains one.

TnT or nitroglycerin is much more dangerous in spite of much lower energy density because the energy is all in the TnT.

Of course this isn't the only consideration (the fact that TnT releases nitrogen which suddenly wants to be much bigger is important, for example), but it is a reason to hesitate around such a battery and carefully consider whether you want to throw it around at 100km/h.

Re: Stabilization of gamma sulfur at room temperature to use in Li-S batteries

#25

Post by Klinky »

Schroedingersat wrote: post #24
Klinky wrote: post #23

Earlier quoted context omitted.

Perhaps I am misunderstanding, but that sounds almost like a calculation that applies to a vacuum, not a pressurized atmosphere with plenty of "free" oxygen? Perhaps that's the same for the TNT & battery, so maybe none of these calculations are directly applicable to real-world scenarios?

The point is the kg of hydrocarbon is less able to release its 40MJ all at once because the oxygen which is spread out over 4000 times as much volume needs to get to it. The battery contains both ends of the reaction, but the hydrocarbon only contains one. TnT or nitroglycerin is much more dangerous in spite of much lower energy density because the energy is all in the TnT. Of course this isn't the only consideration…

I could see the concern, though a car is basically always going to require you to drive around with a potentially lethal amount of energy regardless of the storage medium. Also a battery failure does not mean all energy is released simultaneously. A denser battery could result in a smaller battery that could be better protected from damage.

Re: Stabilization of gamma sulfur at room temperature to use in Li-S batteries

#26

Post by Schroedingersat »

Klinky wrote: post #25
Schroedingersat wrote: post #24

Earlier quoted context omitted.

The point is the kg of hydrocarbon is less able to release its 40MJ all at once because the oxygen which is spread out over 4000 times as much volume needs to get to it. The battery contains both ends of the reaction, but the hydrocarbon only contains one. TnT or nitroglycerin is much more dangerous in spite of much lower energy density because the energy is all in the TnT. Of course this isn't the only consideration…

I could see the concern, though a car is basically always going to require you to drive around with a potentially lethal amount of energy regardless of the storage medium. Also a battery failure does not mean all energy is released simultaneously. A denser battery could result in a smaller battery that could be better protected from damage.

Depends on the battery a bit. Some NMC chemistries are not far off of it. LFP is far safer. Aqueous sodium ion is nit far from LFP energy density and it'll just boil a bit even if you put one in a blender. From the stats and elements involved, LiS is terrifying, but it could be completely fine to put nails through it.
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