Comment by antisthenes
2 days ago
When to comes to batteries, you have to look at multiple factors.
Focusing on just 1, e.g. cycles doesn't give you the whole picture.
1. What is the capacity per $?
2. What is the capacity per kg?
3. What is the capacity per unit of volume?
4. Ease of disposal and recycling
5. Charge and discharge rates.
6. Safety.
7. Viable to produce commercially en masse?
There are just off the top of my head, and not necessarily in that order. The priority will vary depending on your use case.
There is no doubt about lithium-sulfur batteries being excellent and better than existing lithium-based batteries for conditions 1, 2, 4 and 7.
Depending on their structure, there may be problems to be solved about their safety and the resistance to corrosion of their components, which may limit the lifetime to lower values than expected from the number of cycles supported by the electrodes.
Here the sulfur is contained in some kind of borophosphate glass, which should not be easily flammable, so safety or corrosion problems are unlikely.
An essential component of this new battery is iodine, which has an active redox role, together with lithium and sulfur, iodine being an intermediary in the passing of electrons between lithium and sulfur. Iodine is a rather rare element. Fortunately its extraction from sea water is very cheap, but nonetheless the total amount of available iodine is quite limited, so hopefully the battery needs much less iodine than lithium and sulfur.
> Fortunately its extraction from sea water is very cheap, but nonetheless the total amount of available iodine is quite limited,
Huh? I don't know anything about this, but sea water is very plentiful so if that's where we get it how can the amount available be limited?
Sea water is plentiful, but iodine is less that 60 milligrams per ton of water.
If the production of such batteries would require thousands of tons of iodine per year, that would require the processing of billions of tons of sea water per year, from which the iodine would be removed.
Moreover, I do not know the current prices, because in recent years the metal exchanges have become more and more secretive, but some years ago iodine was about 6 times more expensive than lithium, so if a large amount of it were required for such a battery it could raise its price.
Hopefully the amount of iodine used in such batteries would be low, because the amount of needed iodine is proportional with the power of the battery, but it should not depend on the amount of energy stored in the battery (because iodine is an intermediary in the electron flow, it determines the maximum current during charge and discharge, but it is not an endpoint for electrons, so it does not determine the amount of stored energy).
To add a few other factors:
1. Performance in hot/cold environment
2. Safety can be broken down to chemical toxicity, and thermal stability (likelihood to catch on fire)
3. Ability to hold a full charge for extended periods of time (self discharge rate)
One of the drawbacks to li-s is that it had terrible cycle life. This is interesting/exciting because they've found a technique to overcome a major disadvantage to a chemistry that ticks a lot of the other checkboxs you've listed.
The question now is manufacturing, is this something you can use at scale to make batteries.
This is research. You should be focusing on "what's new, and is it interesting" not "is the thing they made a good product".
That said, Li-S typically looks good with respect to potential cost if mass produced (cheap materials), and density metrics. The papers abstract has absurdly good things to say about charge rates. All-solid batteries are typically going to be very safe. So at a glance this research is at least in a very commercializable direction.
>All-solid batteries are typically going to be very safe
Sulfur melts at 115 °C though, so when it overheats, it's not solid anymore. But then, it's apparently not just sulfur, but sulfur embedded in some other stuff, so who knows.
Here the sulfur is contained in some kind of borophosphate glass, which should have a significantly higher melting point.
Last I heard of Li-S batteries about 10 years ago, they were fantastic at energy density and safety, looked like they could be pretty cheap to make, but they only lasted about 10 charge cycles, so this is pretty exciting.
Right. All battery articles, to be taken seriously, need a little table with those numbers. There are many battery technologies which look good on some of those numbers but are so bad on others that the technology is useless.
this has a chart
https://www.batterypowertips.com/how-could-advances-in-solid...
and other variants are commonly used
Exactly. For example the weight of a battery matters very little if used in a stationary application such as a BESS/UPS. But it's very important for transportation e.g. traction power
One shouldn't discount the cost of just mass. Feels to me eventually products costs are based on manufacturing complexity, material costs, and energy. Material costs themselves are often energy per unit mass.
Oh, and another reason why high cycle count may not even be relevant - the battery may become technologically obsolete and non-viable to operate long before it reaches anywhere near the projected cycle count.
So very high cycle counts (e.g. anything above 4000 cycles ~ 10 years of use) should be taken with a very large grain of salt and may be completely irrelevant for practical uses, unless the application calls for multiple daily discharges (if that's the case, why not use a supercapacitor?)