4 ms·

so I'm a bit confused - lithium has a higher electronegativity than sodium. why bother with sodium at all? cost ?

jeffbee 5y ago
They don't sell it very well on this page, do they? The weird diagram at the bottom seems to highlight faster charging and better low-temperature performance. I don't know if the world is clamoring for those. Perhaps also the ready availability of sodium compared to lithium?
- ehnto 5y ago
  Cars are somewhat taken for granted in their ability to work in a wide temperature gamut, so I think improving extreme cold performance is something needed to make sure they stay on par or outperform internal combustion engines. As well, heavy industries around the world are looking at ways to electrify their fleets of vehicles working in remote sometimes extreme weather sites. This includes mining sites and marine operations, even consider that airplanes are an eventual target for EV. Also, charge speed is would surely be the number one gripe for EV ownership, range and performance is pretty much comparable to modern ICE but charge speed, not even close.
  - kwhitefoot 5y ago
    > charge speed is would surely be the number one gripe for EV ownership As far as I can tell this mostly only a concern among those who do not own an EV.
    - steveBK123 5y ago
      Yes, exactly. It's the big bugbear of non-EV owners, but generally irrelevant to actual EV owners. Charger network size, reliability, locations, and pricing matters more. I am also not amongst the superhumans on the internet who can drive 300mi without my bladder/stomach/legs crying out for a break first. Being in NYC, the first hour of every trip is at 20mph, the second hour is average about 50mph, and then only if I am going beyond 70mi do I start to hit average speed about 60mph. Supercharging for ~100mi on the highway is a parallel operation to your bathroom/food break, so its 10 minutes you were already going to use. Gas fill ups are 5 minute serial operations that you either do before or after using the rest area. I suppose if you were on a cannonball run, you could pee in a bottle while pumping gas but I think we can exclude that edge case.
      - mrfusion 5y ago
        I hadn’t thought of that point before. You really can’t leave while pumping gas. So electric charging time is more productive.
  - ajross 5y ago
    Cars are also active devices with comparatively rapid cycle times that can spend a little energy to heat the batteries. EV batteries don't need to stay cold for very long, basically. Note that, contra the way it's often explained, cold batteries lose capacity, not energy. If you take a full battery and put it in the freezer, you'll be unable to drain the full charge but it'll come back when it warms up. Think about it: the back of an envelope will show you that if that energy were actually being "lost" from a cold battery, then the battery must actually be very, very hot, because the energy would have had to go somewhere.
  - steveBK123 5y ago
    Everyone has different use cases, but moving to a marketplace with a variety of cell types & corresponding tradeoffs (high range/moderate charge rate vs moderate range/high charge rate, etc) would be great. Less temperature sensitivity to the range & charge rate would be a huge win. Otherwise, personally charge rate hasn't been much of a problem because I'm not a big road tripper & have a charger at home. 300mi+ battery means I can drive 2 hours to see my parents & back 2 hours without charging, or drive down 4 hours to see my sister.. which means I'm going to be stopping along the way anyway, and charge 100mi+ while in the rest stop using the restroom, or more if I get a coffee or lunch. In everyday driving, charge at home off-peak starting 11pm, then its basically irrelevant whether I can unplug at 11:30pm vs 3am. Charging an EV takes longer, but generally its either at home or at a place you are already doing something else - shopping at Target, getting a coffee at Starbucks, making a pit stop on the highway, etc. Few regular EV drivers just sit in their car for 20min staring into space while they charge.
detaro 5y ago
Cost plays a role, yes. Sodium is extremely common, which is helpful when Lithium is in high demand, the batteries apparently also don't need cobalt (which is also rare, and fraught with ethics concerns around the mining of the main sources in the Democratic Republic of the Congo).
MaKey 5y ago
Mainly costs, but also: Better thermal stability, better performance at low temperatures, better cycle performance.
- Retric 5y ago
  Nothing was said about cycle performance beyond an improvement relative to other sodium batteries. Which suggests it’s at best similar to lithium ion, and possibly still falling behind.
jsjohnst 5y ago
From the key data post someone made above, 90% capacity at -20ºC is a huge win over lithium. Lithium batteries have a severely hard time in cold weather and must be heated to retain capacity.
- mrfusion 5y ago
  So you could include a couple lb sodium battery to power heating your main battery.
elihu 5y ago
Cost is a pretty big reason. Tesla has made somewhere around one and a half million cars. If you want to make a billion cars, that's a whole different situation. the resources needed to make the batteries could become pretty severe bottlenecks. I think that's something that's often missed in EV discussions that focus on range and who has the best 0-60 time and so on: luxury car features are nice, but in the end what matters more is who can actually make the cheapest good-enough battery at the highest volume, because that's what's going to be in most of the world's cars. Wherever those batteries are made could basically be what Saudi Arabia was to the era of gas-powered vehicles. (Though to be fair you can build a battery factory almost anywhere, whereas oil is something you either have in abundance or you don't.) Not sure what the inputs are to these sodium ion batteries, but most lithium ion batteries require cobalt, nickel, and lithium. Lithium iron phosphate has an advantage that it doesn't require cobalt or nickel.
pfdietz 5y ago
In a Li-ion battery, the oxidation state of Li never changes, so its electronegativity is not terribly important. What's being oxidized/reduced are elements in the electrodes, like iron.
sunstone 5y ago
To some extent EV batteries can trade off recharge rate for power density. That is, if you can recharge your battery in five minutes you might not care as much that it's range is only 200km. The sodium batteries do have high recharge rates and lower cost. Not to mention being better in the cold. These attributes make it a good complement for lithium ion and it looks like CATL already has such a battery already to at least the prototype stage.

They don't sell it very well on this page, do they? The weird diagram at the bottom seems to highlight faster charging and better low-temperature performance. I don't know if the world is clamoring for those. Perhaps also the ready availability of sodium compared to lithium?

ehnto 5y ago
Cars are somewhat taken for granted in their ability to work in a wide temperature gamut, so I think improving extreme cold performance is something needed to make sure they stay on par or outperform internal combustion engines. As well, heavy industries around the world are looking at ways to electrify their fleets of vehicles working in remote sometimes extreme weather sites. This includes mining sites and marine operations, even consider that airplanes are an eventual target for EV. Also, charge speed is would surely be the number one gripe for EV ownership, range and performance is pretty much comparable to modern ICE but charge speed, not even close.
- kwhitefoot 5y ago
  > charge speed is would surely be the number one gripe for EV ownership As far as I can tell this mostly only a concern among those who do not own an EV.
  - steveBK123 5y ago
    Yes, exactly. It's the big bugbear of non-EV owners, but generally irrelevant to actual EV owners. Charger network size, reliability, locations, and pricing matters more. I am also not amongst the superhumans on the internet who can drive 300mi without my bladder/stomach/legs crying out for a break first. Being in NYC, the first hour of every trip is at 20mph, the second hour is average about 50mph, and then only if I am going beyond 70mi do I start to hit average speed about 60mph. Supercharging for ~100mi on the highway is a parallel operation to your bathroom/food break, so its 10 minutes you were already going to use. Gas fill ups are 5 minute serial operations that you either do before or after using the rest area. I suppose if you were on a cannonball run, you could pee in a bottle while pumping gas but I think we can exclude that edge case.
    - mrfusion 5y ago
      I hadn’t thought of that point before. You really can’t leave while pumping gas. So electric charging time is more productive.
- ajross 5y ago
  Cars are also active devices with comparatively rapid cycle times that can spend a little energy to heat the batteries. EV batteries don't need to stay cold for very long, basically. Note that, contra the way it's often explained, cold batteries lose capacity, not energy. If you take a full battery and put it in the freezer, you'll be unable to drain the full charge but it'll come back when it warms up. Think about it: the back of an envelope will show you that if that energy were actually being "lost" from a cold battery, then the battery must actually be very, very hot, because the energy would have had to go somewhere.
- steveBK123 5y ago
  Everyone has different use cases, but moving to a marketplace with a variety of cell types & corresponding tradeoffs (high range/moderate charge rate vs moderate range/high charge rate, etc) would be great. Less temperature sensitivity to the range & charge rate would be a huge win. Otherwise, personally charge rate hasn't been much of a problem because I'm not a big road tripper & have a charger at home. 300mi+ battery means I can drive 2 hours to see my parents & back 2 hours without charging, or drive down 4 hours to see my sister.. which means I'm going to be stopping along the way anyway, and charge 100mi+ while in the rest stop using the restroom, or more if I get a coffee or lunch. In everyday driving, charge at home off-peak starting 11pm, then its basically irrelevant whether I can unplug at 11:30pm vs 3am. Charging an EV takes longer, but generally its either at home or at a place you are already doing something else - shopping at Target, getting a coffee at Starbucks, making a pit stop on the highway, etc. Few regular EV drivers just sit in their car for 20min staring into space while they charge.

detaro 5y ago

Cost plays a role, yes. Sodium is extremely common, which is helpful when Lithium is in high demand, the batteries apparently also don't need cobalt (which is also rare, and fraught with ethics concerns around the mining of the main sources in the Democratic Republic of the Congo).

MaKey 5y ago

Mainly costs, but also: Better thermal stability, better performance at low temperatures, better cycle performance.

Retric 5y ago
Nothing was said about cycle performance beyond an improvement relative to other sodium batteries. Which suggests it’s at best similar to lithium ion, and possibly still falling behind.

jsjohnst 5y ago

From the key data post someone made above, 90% capacity at -20ºC is a huge win over lithium. Lithium batteries have a severely hard time in cold weather and must be heated to retain capacity.

mrfusion 5y ago
So you could include a couple lb sodium battery to power heating your main battery.

elihu 5y ago

Cost is a pretty big reason. Tesla has made somewhere around one and a half million cars. If you want to make a billion cars, that's a whole different situation. the resources needed to make the batteries could become pretty severe bottlenecks. I think that's something that's often missed in EV discussions that focus on range and who has the best 0-60 time and so on: luxury car features are nice, but in the end what matters more is who can actually make the cheapest good-enough battery at the highest volume, because that's what's going to be in most of the world's cars. Wherever those batteries are made could basically be what Saudi Arabia was to the era of gas-powered vehicles. (Though to be fair you can build a battery factory almost anywhere, whereas oil is something you either have in abundance or you don't.) Not sure what the inputs are to these sodium ion batteries, but most lithium ion batteries require cobalt, nickel, and lithium. Lithium iron phosphate has an advantage that it doesn't require cobalt or nickel.

pfdietz 5y ago

In a Li-ion battery, the oxidation state of Li never changes, so its electronegativity is not terribly important. What's being oxidized/reduced are elements in the electrodes, like iron.

sunstone 5y ago

To some extent EV batteries can trade off recharge rate for power density. That is, if you can recharge your battery in five minutes you might not care as much that it's range is only 200km. The sodium batteries do have high recharge rates and lower cost. Not to mention being better in the cold. These attributes make it a good complement for lithium ion and it looks like CATL already has such a battery already to at least the prototype stage.