5 ms·

> it is only capable of 150 cycles of charging and discharging for the time being. At the present stage, the energy density of the battery is also only able to

> it is only capable of 150 cycles of charging and discharging for the time being. At the present stage, the energy density of the battery is also only able to reach around 220 Wh/kilo, which is only around 55-60% of the 350 Wh/kilo of energy density for lithium-ion battery. Key Point

zelon88 7y ago
I noticed in the beginning of the article they claim greater capacity than Li-Ion and then contradict that statement in your quote. Curious to see how that gets reconciled.
- TylerE 7y ago
  Iron is considerably denser than lithium, so it would have a higher capacity for a given volume.
  - taneq 7y ago
    It's interesting how this tradeoff works. Lighter elements have a higher ratio of electrons to total mass, so they can store more chemical energy per kilogram, but are also less dense so they store less chemical energy per volume. Of course, chemistry being what it is, it's not that straightforward. Here's a chart of atomic mass and specific gravity against atomic number: http://mrtitanium.com/images/density.gif?lbisphpreq=1 http://mrtitanium.com/images/density.gif?lbisphpreq=1 If you look for elements with a high ratio of density to atomic weight, you'll find most of the elements that we typically use in batteries (eg. Lithium, Magnesium, Aluminium, Manganese, Iron, Nickel, Cobalt, Silver). Edit: Changed 'atomic number' to 'atomic weight' in the last paragraph.
  - Gibbon1 7y ago
    Also metallic iron anode. I think an issue with alkali ion batteries is you need zeolite electrodes which adds bulk weight. Thus doing a number on your energy to weight ratio.
seanmcdirmid 7y ago
They can get better with additional prototypes. They might hit a wall with further development, but they at least think they want.
lettergram 7y ago
While true, Iron is much more accessible than Lithium. Which potentially would make it cheaper per pound (eventually). Today that’s not the case, but with time, who knows. Still interesting.
- robocat 7y ago
  I think the Lithium content makes up about 5% of the cost of a battery from this comment: "By 2025, the market for mined lithium raw material may be worth $20 billion, compared with $43 billion for refined products and $424 billion for battery cells" in https://www.bloomberg.com/news/articles/2019-07-28/the-lithium-mine-buildup-is-outpacing-the-electric-car-boom https://www.bloomberg.com/news/articles/2019-07-28/the-lithi...
flukus 7y ago
The 150 cycles is a killer, as is the energy density in certain circumstances, But for something less space conscious like home or commercial energy storage would it matter if it's (I assume) cheaper? Even 150 cycles might be fine for things that discharge very slowly, like a battery in a fire alarm.
taneq 7y ago
The cycle life isn't too bad given that this is still at the "it works at all" stage, not the "refined to be commercially viable" stage. Remember that 20 years ago the only practical bulk storage battery was lead acid and that had a similar cycle life. We're just spoiled these days with LiIon and LiPoly being so cheaply available. Also the per-kilogram energy storage is far less important given the price difference between iron and lithium. There's a huge market for stationary battery storage where weight and even (to a lesser extent) size are non-factors compared with cost per kWh.
- mc32 7y ago
  This is pretty cool. While lithium isn’t that scarce iron is plentiful. Also would be even nicer if it used fewer heavy metals and rare earth elements.
  - nine_k 7y ago
    Lithium is also quite plentiful, not rare at all. It's also not poisonous the way lead or cadmium are. Lithium batteries are a fire hazard, though, even if we learn to produce them 10x as cheap in the future. Iron batteries are most likely not.
- klyrs 7y ago
  Stationary storage sounds like a killer app. 150 charge cycles doesn't sound like much, but if you're using these in combination with solar power, the batteries could serve for almost half a year.
  - D_Alex 7y ago
    Yes, for some stationary storage applications 150 cycles would be completely adequate, and would last for many years. Eg: replacement of emergency generators, or some peaking power stations which only operate for a few days per year (we have lots of these in Australia).
    - rohan_shah 7y ago
klingonopera 7y ago
That's some pretty insane energy density for a prototype vs. years of R&D into a mature technology. Hope they can improve the charging cycles. Anyone has a clue what the numbers on the matured Lithium-Ion tech is for comparison?

zelon88 7y ago

I noticed in the beginning of the article they claim greater capacity than Li-Ion and then contradict that statement in your quote. Curious to see how that gets reconciled.

TylerE 7y ago
Iron is considerably denser than lithium, so it would have a higher capacity for a given volume.
- taneq 7y ago
  It's interesting how this tradeoff works. Lighter elements have a higher ratio of electrons to total mass, so they can store more chemical energy per kilogram, but are also less dense so they store less chemical energy per volume. Of course, chemistry being what it is, it's not that straightforward. Here's a chart of atomic mass and specific gravity against atomic number: http://mrtitanium.com/images/density.gif?lbisphpreq=1 http://mrtitanium.com/images/density.gif?lbisphpreq=1 If you look for elements with a high ratio of density to atomic weight, you'll find most of the elements that we typically use in batteries (eg. Lithium, Magnesium, Aluminium, Manganese, Iron, Nickel, Cobalt, Silver). Edit: Changed 'atomic number' to 'atomic weight' in the last paragraph.
- Gibbon1 7y ago
  Also metallic iron anode. I think an issue with alkali ion batteries is you need zeolite electrodes which adds bulk weight. Thus doing a number on your energy to weight ratio.

seanmcdirmid 7y ago

They can get better with additional prototypes. They might hit a wall with further development, but they at least think they want.

lettergram 7y ago

While true, Iron is much more accessible than Lithium. Which potentially would make it cheaper per pound (eventually). Today that’s not the case, but with time, who knows. Still interesting.

robocat 7y ago
I think the Lithium content makes up about 5% of the cost of a battery from this comment: "By 2025, the market for mined lithium raw material may be worth $20 billion, compared with $43 billion for refined products and $424 billion for battery cells" in https://www.bloomberg.com/news/articles/2019-07-28/the-lithium-mine-buildup-is-outpacing-the-electric-car-boom https://www.bloomberg.com/news/articles/2019-07-28/the-lithi...

flukus 7y ago

The 150 cycles is a killer, as is the energy density in certain circumstances, But for something less space conscious like home or commercial energy storage would it matter if it's (I assume) cheaper? Even 150 cycles might be fine for things that discharge very slowly, like a battery in a fire alarm.

taneq 7y ago

The cycle life isn't too bad given that this is still at the "it works at all" stage, not the "refined to be commercially viable" stage. Remember that 20 years ago the only practical bulk storage battery was lead acid and that had a similar cycle life. We're just spoiled these days with LiIon and LiPoly being so cheaply available. Also the per-kilogram energy storage is far less important given the price difference between iron and lithium. There's a huge market for stationary battery storage where weight and even (to a lesser extent) size are non-factors compared with cost per kWh.

mc32 7y ago
This is pretty cool. While lithium isn’t that scarce iron is plentiful. Also would be even nicer if it used fewer heavy metals and rare earth elements.
- nine_k 7y ago
  Lithium is also quite plentiful, not rare at all. It's also not poisonous the way lead or cadmium are. Lithium batteries are a fire hazard, though, even if we learn to produce them 10x as cheap in the future. Iron batteries are most likely not.
klyrs 7y ago
Stationary storage sounds like a killer app. 150 charge cycles doesn't sound like much, but if you're using these in combination with solar power, the batteries could serve for almost half a year.
- D_Alex 7y ago
  Yes, for some stationary storage applications 150 cycles would be completely adequate, and would last for many years. Eg: replacement of emergency generators, or some peaking power stations which only operate for a few days per year (we have lots of these in Australia).
  - rohan_shah 7y ago

klingonopera 7y ago

That's some pretty insane energy density for a prototype vs. years of R&D into a mature technology. Hope they can improve the charging cycles. Anyone has a clue what the numbers on the matured Lithium-Ion tech is for comparison?