Researchers propose new aluminum–sulfur battery with molten-salt electrolyte; low-cost, rechargeable, fire-resistant, recyclable
25 August 2022
An international team of researchers led by Quanguan Pang at Peking University and Donald Sadoway at MIT reports a bidirectional, rapidly charging aluminum–chalcogen battery operating with a molten-salt electrolyte composed of NaCl–KCl–AlCl3. This differs from other aluminum batteries in the choice of a positive elemental-chalcogen electrode as opposed to various low-capacity compound formulations and in the choice of a molten-salt electrolyte as opposed to room-temperature ionic liquids that induce high polarization.
The multi-step conversion pathway between aluminium and chalcogen allows rapid charging at up to 200C, and the battery endures hundreds of cycles at very high charging rates without aluminum dendrite formation. A paper on the work is published in Nature.
Importantly for scalability, the cell-level cost of the aluminum–sulfur battery is projected to be less than one-sixth that of current lithium-ion technologies. Composed of earth-abundant elements that can be ethically sourced and operated at moderately elevated temperatures just above the boiling point of water, this chemistry has all the requisites of a low-cost, rechargeable, fire-resistant, recyclable battery.
—Pang et al.
I wanted to invent something that was better, much better, than lithium-ion batteries for small-scale stationary storage, and ultimately for automotive.
—Donald Sadoway
The researchers showed that the charging rate was highly dependent on the working temperature, with 110 degrees Celsius (230 degrees Fahrenheit) showing 25 times faster rates than 25 C (77 F).
The molten salt the team chose as an electrolyte simply because of its low melting point turned out to have a fortuitous advantage. One of the biggest problems in battery reliability is the formation of dendrites, which are narrow spikes of metal that build up on one electrode and eventually grow across to contact the other electrode, causing a short-circuit and hampering efficiency. But this particular salt, it happens, is very good at preventing that malfunction.
The battery requires no external heat source to maintain its operating temperature. The heat is naturally produced electrochemically by the charging and discharging of the battery.
This new battery formulation, Sadoway says, would be ideal for installations of about the size needed to power a single home or small to medium business, producing on the order of a few tens of kilowatt-hours of storage capacity.
For larger installations, up to utility scale of tens to hundreds of megawatt hours, other technologies might be more effective, including the liquid metal batteries Sadoway and his students developed several years ago and which formed the basis for a spinoff company called Ambri, which hopes to deliver its first products within the next year.
The smaller scale of the aluminum-sulfur batteries would also make them practical for uses such as electric vehicle charging stations, Sadoway says. He points out that when electric vehicles become common enough on the roads that several cars want to charge up at once, as happens today with gasoline fuel pumps, “if you try to do that with batteries and you want rapid charging, the amperages are just so high that we don’t have that amount of amperage in the line that feeds the facility.” Having a battery system such as this to store power and then release it quickly when needed could eliminate the need for installing expensive new power lines to serve these chargers.
The new technology is already the basis for a new spinoff company called Avanti, which has licensed the patents to the system, co-founded by Sadoway and Luis Ortiz ’96 ScD ’00, who was also a co-founder of Ambri. Sadoway is formally the Chief Scientific Advisor.
The research team included members from Peking University, Yunnan University and the Wuhan University of Technology, in China; the University of Louisville, in Kentucky; the University of Waterloo, in Canada; Oak Ridge National Laboratory, in Tennessee; and MIT. The work was supported by the MIT Energy Initiative, the MIT Deshpande Center for Technological Innovation, and ENN Group.
Resources
Pang, Q., Meng, J., Gupta, S. et al. (2022) “Fast-charging aluminium–chalcogen batteries resistant to dendritic shorting.” Nature 608, 704–711 doi: 10.1038/s41586-022-04983-9
Sounds interesting.
I am not keen on using lithium batteries for storage, relatively scarce resources, or at least ones which it will take some time to expand, mean that they are far better deployed in transport, where their high power and specific energy are critical.
Incidentally, I had a look at the energy density of aluminum batteries, and theoretically ( ;-) ) at least, it can be extraordinarily high.
This seems to be firmly focused on stationary storage though.
Posted by: Davemart | 25 August 2022 at 03:53 AM
@Dave, you ask an important question:
Where is the best place to have batteries:
In individual homes,
At grid level or
In EVs or
In EV charging stations.
IMO, individual homes works well for wealthy people with a head for tech, but are too expensive for the general population and typically only help one home at a time.
Grid storage is better in that the benefits are distributed across the grid and it can be managed and maintained by professionals.
Evs are good in that it displaces HC fuels and pollution (at EV level anyway).
Charging station batteries are required to make charging stations work properly, and while they sound like a duplication, could be synched together to work like a gird system as well.
Also, you could "phone ahead" to tell the station to make sure that it would have enough kWh available for when you get there in say 10-20 minutes time.
Would also work well with solar charging stations (essential really).
+ these batteries sound very interesting.
Posted by: mahonj | 25 August 2022 at 04:37 AM
Nice!
200C charging rate, 96% round trip energy efficiency, 1/10th the cost of today's lithium batteries, reasonable # of cycles (10% loss over 200 cycles), energy density >500 Wh/L.
Posted by: matt | 25 August 2022 at 10:02 AM
Unfortunately, Sadoway has an history of over-promising and under-delivering. I have no access to the paper, so I can check the data but it sounds to me this is a short lifespan chemistry.
There have been several studies and projects on aluminium-sulfur batteries at room temperature (one of them close to my city, "Albufera energy"). Most of them seem to suffer of short lifespans.
Posted by: peskanov | 25 August 2022 at 03:49 PM
Hi peskanov:
I share your reservations about miracle batteries in general, which have a long sad history.
Unfortunately even as august bodies as the DOE have pretty much swallowed the stuff put out by interested parties about the 'inevitable march of progress' for battery technologies, so their projections included, remarkably, the assumption that lithium air batteries will be up and running and economic.
Lovely, if it happens.
But inevitable, it sure ain't, not within the timeframe assumed, certainly.
Posted by: Davemart | 26 August 2022 at 02:33 AM
Davemart,
I found a bit of extra info on this pdf:
https://techxplore.com/pdf580542113.pdf
They have created a new company to develop this chemistry. I guess that's good news, because Sadoway already created Ambri and they developed a real battery over the years...although that battery turned to be much worse than the one Sadoway promised initially.
Posted by: peskanov | 26 August 2022 at 02:52 AM
@peskanov
Yeah, and they have published in Nature which indicates that there is probably some real science behind their claims.
With battery technology it is usually the bits they have not mentioned that cause the problems though, so they have often improved one metric at the expense of others.
Posted by: Davemart | 26 August 2022 at 05:19 AM
"With battery technology it is usually the bits they have not mentioned that cause the problems though, ...."
I couldn't agree more with you, its the same procedure determining H2 tech.
Posted by: yoatmon | 26 August 2022 at 06:32 AM
@yoatman:
Yep, a critical stance is needed for any technology.
However, battery tech is more mature than fuel cells, and gains are harder to come by.
Very large improvements and reductions in cost are a verifiable fact in fuel cells.
I remember not so long ago having discussions with anti fuel cell folk who were claiming that a fuel cell car costs half a million dollars, which was correct at the time, and always would, which was nonsense.
They were confounding prototype costs with mass production costs, and ignoring incremental improvement.
Scepticism is fine, and valuable.
Wilful dismissal of technologies on specious grounds is another matter.
Posted by: Davemart | 26 August 2022 at 07:30 AM
@yoatman:
I would add that a couple of years back I called out Nikola's claims on fuel cell trucks as nonsense, on Seeking Alpha. as they were doing exactly the same stuff with exaggerated claims.
Since then the head of the company has been dismissed for that reason, and the company now has more sober leadership.
I'm pretty agnostic is calling out nonsense, batteries, fuel cells, whatever.
Posted by: Davemart | 26 August 2022 at 07:34 AM
The weakness seems to be the number of cycles, which is of the order of "hundreds" of cycles.
If you had 200 cycles, it wouldn't last 7 months in a house if cycled once per day.
+ once you put it into production and wide scale use, you will find out how it really works.
Posted by: mahonj | 26 August 2022 at 09:42 AM
@mahonj,
those 200 cycles seems to happen under pretty extreme conditions (charging under less than a minute!).
I have not seen cycling graphs for something more useful, like charging at C3, 1C or just fast charging at 5C.
Posted by: peskanov | 26 August 2022 at 10:37 AM
@mahonj:
Before one can address any critique including cycle life, the criticism has to be way more specific.
There are multiple types of fuel cells, and variations within those types.
In cars low temperature PEMS are usually used, and those are the ones which use precious metals too.
For trucks etc just as in diesel trucks, way more attention has to be and is paid to longevity, shooting for the half a million to a million miles a diesel truck lasts for.
For aircraft they are hoping to use high temperature PEMS, which is a different ball game.
But then there are also stationary power versions, where concern over cycle life is predicated on how often you want to cycle it.
Then there are SOFCs, and AEMs which are radically different.
You mention claims of 200 cycles, without any reference to what fuel cell you are talking about at all, and express concerns about its use, whatever fuel cell you are referring to, in a home setting.
Well, there are hundreds of thousands of home fuel cells in Japanese homes right now, half of them made by Panasonic, starting a decade ago, and there are no signs of them clapping out:
https://www.panasonic.com/uk/corporate/sustainability/products-and-solutions/hydrogen-fuel-cells.html
What are you talking about?
I am baffled.
Posted by: Davemart | 26 August 2022 at 10:59 AM
@Davemart,
I believe mahonj was not addressing you, but talking about the aluminium-sulfur battery ( 200 cycles are mentioned in the article).
Posted by: peskanov | 26 August 2022 at 12:58 PM
@peskanov:
Aha! That makes sense! Mahonj usually does, which was partly why I was baffled when I failed to parse his comment.
I have not got access to the Nature article, so the 200 cycles with 10% loss only appears in Matt's comment, which helped confuse me.
@mahonj:
I was lost there for a while, so it is great that peskanov has clarified!
When I said:
' What are you talking about?
I am baffled.'
I meant literally that, and was certainly not making a claim that you weren't making sense, but that I could not follow you at all as to what you were arguing.
Posted by: Davemart | 26 August 2022 at 01:38 PM
@peskanov
FYI, The first page of their paper is on researchgate, and includes Fig 4 d and e describing loss of capacity/cycle # at 5C, 10C, 50C and 100C over 200 cycles; fig g gives density comparison with other batteries, fig h gives cost comparisons.
Posted by: matt | 26 August 2022 at 03:16 PM
@matt,
thanks, the graphs are very interesting, specially those charging at 5C & 10C, as they reach the 500 cycles count. These seem to be at 90% capacity after those 500 cycles.
It's certainly an intriguing cell chemistry.
Posted by: peskanov | 26 August 2022 at 03:31 PM