Stabilization of gamma sulfur at room temperature to use in Li-S batteries | Hacker News Reader

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

nature.com

33 pointsPhithagoras25 comments

The "notorious polysulfide shuttling effect" mentioned in the first sentence of the abstract is a pretty big understatement. It's basically an automatic death sentence for Li-S batteries in commercial applications, so the fact that this paper claims to have _zero_ polysulfide formation is pretty remarkable.

Short primer: The polysulfide shuttling effect is a phenomenon that can occur in lithium-sulfur batteries. It occurs when polysulfide ions, which are intermediates formed during the discharge and charging of the battery, are able to move from the cathode to the anode. This causes a decrease in the overall capacity of the battery.

To prevent this from happening, a separator with a high ionic resistance is used to physically block the movement of the polysulfides, but this increases the bulk and form factor of the battery, which makes it less suitable for applications like phones and laptops.

Other sources say 4000 cycles in one year of testing and the battery is still going strong. Apparently they used some chemical vapor deposition to dope sulfur in a carbon mesh, and apparently gamma sulfur was created in the process, which was accidental, they're trying to determine why their process created it.

Claim 3x the capacity of current lithium ion. That would be, what 600 wh/kg? 750? That seems unbelievable.

The energy density is the reason Li-S batteries are researched in the first place. Other prototypes of Li-S batteries according to Wikipedia already archived 450 Wh/kg.

4000 cycles is pretty impressive. Worth pointing out just how good that is: if you fully charge the battery every day of the year, that would mean close to 11 years of very intensive use. 4000 times a typical maximum range of 250 miles would mean driving a million miles. Some taxis get that kind of mileage of course. But most drivers would take quite a bit of time to get there.

In short, if you are lucky enough to own a vehicle with such a battery, it needing replacement is not going to be an event that you should have to worry about for decades if you drive it normally. Which would mean doing about 14K miles per year; or about 71 years.

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.

Gasoline has 40 megajoules per kilo.

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.

The key difference is the hydrocarbon "battery" has a volumetric energy density of around 12kJ/L if you include both halves where the sulfur one is still around 7MJ/L

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?

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.

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.

And it's far more common for ICE cars to actually explode/burn out. And particularly petrol fires can be very dangerous and lethal. Cars can combust while parked, while driving, or when you get in an accident. It's one of the most common causes for fire brigades to have to take some action. Diesel is a bit safer than petrol but it will burn if things get hot enough. And cars and trucks overheat and catch fire for all sorts of reasons.

EVs are much safer both in absolute numbers and relative numbers (if you consider there are far less EVs than ice vehicles). They do occasionally burn of course. And usually those fires aren't very explosive and give you plenty of time to get out of the vehicle and to safety. Fatalities/injuries are rare with this.

Petrol cars do not explode with any frequency.

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.

Interesting. This lead me to this energy density table: https://en.wikipedia.org/wiki/Energy_density_Extended_Refere...

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.

It's nice to see a battery chemistry article that admits they're in the early stages of getting some new chemistry to work. The usual battery article is "we got this to happen in a test tube, huge world-changing breakthough Real Soon Now". Those have become tiresome.

This article seems to have much less bullshit than most. Hope this one works.

It's an academic paper in Nature, it's not CNBC.

more like university press

That means much less than it used to.

Note that this is not particularly new. This paper was published February 2022.

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