3 ms·

I don't know what chemistry exactly these cells are using, but in sodium-ion batteries, prussian blue analogs as they are called are common anode materials. Ove

I don't know what chemistry exactly these cells are using, but in sodium-ion batteries, prussian blue analogs as they are called are common anode materials. Overcharging these cells can lead to a release of hydrogen cyanide gas, notoriously known as Zyklon B. It has damped my enthusiasm for perusing it as a potential future home energy storage solution.

cyberax 7mo ago
Just wait until you find out about hydrogen sulfide from overcharged car batteries. Also, I think HCN can be scrubbed by adding a special absorptive cap onto the battery.
- devwastaken 7mo ago
  hydrogen sulfide is not anywhere in the same category. When you consider failure you have to consider what is the most catastrophic possibility and if that is “this battery silently kills people” then you dont make it.
  - cyberax 7mo ago
    > hydrogen sulfide is not anywhere in the same category. It has the same LD50 dose as HCN. It literally _is_ just as bad. It routinely kills people on oil rigs because in lethal concentrations it immediately shuts off your nose. How often do you hear about people getting poisoned by it from lead-acid batteries?
    - zdragnar 7mo ago
      The only people with any significant amount of lead acid batteries on their property are off grid types who typically store them away from their primary domicile as a fire safety precaution. Fast charging a car/chemical weapon in your garage isn't terribly appealing.
      - Dylan16807 7mo ago
        If that battery is a chemical weapon then so is a big half-plastic box with ten gallons of gasoline inside.
    - gilleain 7mo ago
      Not precisely the same: https://en.wikipedia.org/wiki/Hydrogen_cyanide https://en.wikipedia.org/wiki/Hydrogen_cyanide - 107 ppm (human, 10 min) https://en.wikipedia.org/wiki/Hydrogen_sulfide https://en.wikipedia.org/wiki/Hydrogen_sulfide - 600 ppm (human, 30 min) https://en.wikipedia.org/wiki/Carbon_monoxide https://en.wikipedia.org/wiki/Carbon_monoxide - 4000 ppm (human, 30 min) These are "LCLo" values from the databoxes on those pages. More easily comparable numbers may be around somewhere.
      - WarmWash 7mo ago
        Hydrogen cyanide has the bonus of being mostly odorless too. Whereas hydrogen sulfide is distinctly bad smelling.
        ted_dunning 7mo ago
        Apparently it only smells bad if you have non-lethal concentration.
  - wat10000 7mo ago
    We pipe methane into millions of homes. I don't think "this can silently kill people in the worst case" is enough to block something.
    - zdragnar 7mo ago
      We also have to adulterate that methane with bitter smelling agents too warn people of the danger when there's a leak. The line into the house is also limited by a regulator to ensure the pressure is very low. If gas builds up in a battery, it's either going to leak out slowly or build up and leak out all at once. Very much not an equal comparison.
      - adrian_b 7mo ago
        What the other poster said about the risk of releasing cyanide during overcharging is not true. Cyanide could be released only at high temperatures over 300 Celsius degrees. During a fire, there are many other things in a car that can release toxic fumes easier than a sealed battery.
      - wat10000 7mo ago
        The methane is almost always piped in to be burned, and that can easily create odorless carbon monoxide. And the smell is not foolproof either. This does routinely kill people and we keep doing it. The jurisdictions that are banning it are doing so because of environmental reasons, not safety.
  - adrian_b 7mo ago
    Batteries with Prussian blue cannot kill people silently. Cyanide could be released only at high temperatures, e.g. if the battery is opened and burned, not during normal operation, even if overcharging is not prevented, as it should. The sulfuric acid from the traditional lead-acid car batteries is more dangerous than this.
- UncleOxidant 7mo ago
  Or you could just have the batteries in a separate enclosure away from your house. I think I would be inclined to do this anyway, certainly for Lithium batteries given the possibility of fire.
deleted 7mo ago
[deleted]
hunterpayne 7mo ago
Its metallic sodium. Its about 30 times more volatile than Lithium. We don't use metallic sodium for almost anything industrial because of this volatility. I assumed there would be some mixed Li-Na-ion batteries. A pure Na-ion battery is an explosive waiting to go off. Putting these in a car...seems rather like a poor choice unless you are a personal injury lawyer.
- mlsu 7mo ago
  This is incredibly misleading. It's not like there's a bunch of metallic sodium sitting in the battery waiting to react. It's a lot closer to a solid solution. Do you have a personal injury lawyer on speed dial for your table salt?
  - chromacity 7mo ago
    Your response is even more misleading than the misconception you're trying to correct. The complexes formed in (charged) lithium batteries are unstable and reactive in ways quite similar to the base metal. The salt molecule, in contrast, is pretty unreactive. Salt shakers don't catch fire if dropped.
    - adrian_b 7mo ago
      Which complexes are reactive? The substances similar with Prussian blue are very stable. During charge and discharge, the ionic charge of iron ions varies between +2 and +3 and the structure of the electrode has spaces that are empty when the charge of the iron ions is +3 and they are filled with sodium ions when the charge of the iron ions is +2. Both states of the electrode are very stable, being neutral salts. The composition of the electrolyte does not vary depending on the state of charge of the battery and it is also stable. The only part of the battery that can be unstable is the other electrode, which stores neutral atoms of sodium intercalated in some porous material. If you take a fully charged battery, you cut it and you extract the electrode with sodium atoms, that electrode would react with water, but at a lower speed than pure sodium, so it is not clear how dangerous such an electrode would be in comparison with the similar lithium electrodes.
adrian_b 7mo ago
Do you have any link for the claim that overcharging can produce cyanide? I have never heard such a thing and all the articles that I have seen about overcharging concluded that such batteries are much safer during overcharging than other kinds of batteries, the worst case effect being battery swelling. In normal conditions, even during overcharging there are no obvious chemical reactions that could produce hydrogen cyanide. For instance, at https://pubs.acs.org/doi/10.1021/acsenergylett.4c02915 https://pubs.acs.org/doi/10.1021/acsenergylett.4c02915 it is said that cyanide release can happen only at temperatures above 300 Celsius degrees. Such temperatures cannot be reached in normal conditions.
- MengerSponge 7mo ago
  > Such temperatures cannot be reached in normal conditions Thank you for the reasonable chuckle I got from this understatement of the day.
  - adrian_b 7mo ago
    By normal conditions I mean charging and discharging and even overcharging if the controller is defective. Burning the battery is something that I define as not normal conditions. Many plastics produce toxic fumes when burnt and many such plastics may be used in a car. Burning the battery is not the greatest risk of toxic fumes during a fire. If the fire is intense enough, any released cyanide might also be burned.
    - WarmWash 7mo ago
      The battery heats itself in these failure modes.
      - adrian_b 7mo ago
        Not to 300 Celsius degrees. A battery of any kind can overheat with the output shorted or during excessive overcharging, but normally whenever a battery is used in a device there are protective devices that prevent such events. If there are no protections, the designer is guilty, not the battery. Moreover, such risks are greater for Li-ion batteries, which have flammable electrolyte. Na-ion batteries will replace Li-ion only in certain applications, like stationary energy storage, cars for cold climates and cheaper cars, while Li-ion will remain the choice for maximum energy per kilogram. But it is weird to be concerned about the safety of Na-ion when that is certainly not worse than for Li-ion and most likely it is better.
Toutouxc 7mo ago
Just adding to what others have already said — overcharging the cells is not something you're supposed to be doing. Overcharging even today's common Li-ion cells, i.e. those in your phone, vacuum, EV or home storage, will lead to comparably spectacular results.

cyberax 7mo ago

Just wait until you find out about hydrogen sulfide from overcharged car batteries. Also, I think HCN can be scrubbed by adding a special absorptive cap onto the battery.

devwastaken 7mo ago
hydrogen sulfide is not anywhere in the same category. When you consider failure you have to consider what is the most catastrophic possibility and if that is “this battery silently kills people” then you dont make it.
- cyberax 7mo ago
  > hydrogen sulfide is not anywhere in the same category. It has the same LD50 dose as HCN. It literally _is_ just as bad. It routinely kills people on oil rigs because in lethal concentrations it immediately shuts off your nose. How often do you hear about people getting poisoned by it from lead-acid batteries?
  - zdragnar 7mo ago
    The only people with any significant amount of lead acid batteries on their property are off grid types who typically store them away from their primary domicile as a fire safety precaution. Fast charging a car/chemical weapon in your garage isn't terribly appealing.
    - Dylan16807 7mo ago
      If that battery is a chemical weapon then so is a big half-plastic box with ten gallons of gasoline inside.
  - gilleain 7mo ago
    Not precisely the same: https://en.wikipedia.org/wiki/Hydrogen_cyanide https://en.wikipedia.org/wiki/Hydrogen_cyanide - 107 ppm (human, 10 min) https://en.wikipedia.org/wiki/Hydrogen_sulfide https://en.wikipedia.org/wiki/Hydrogen_sulfide - 600 ppm (human, 30 min) https://en.wikipedia.org/wiki/Carbon_monoxide https://en.wikipedia.org/wiki/Carbon_monoxide - 4000 ppm (human, 30 min) These are "LCLo" values from the databoxes on those pages. More easily comparable numbers may be around somewhere.
    - WarmWash 7mo ago
      Hydrogen cyanide has the bonus of being mostly odorless too. Whereas hydrogen sulfide is distinctly bad smelling.
      - ted_dunning 7mo ago
        Apparently it only smells bad if you have non-lethal concentration.
- wat10000 7mo ago
  We pipe methane into millions of homes. I don't think "this can silently kill people in the worst case" is enough to block something.
  - zdragnar 7mo ago
    We also have to adulterate that methane with bitter smelling agents too warn people of the danger when there's a leak. The line into the house is also limited by a regulator to ensure the pressure is very low. If gas builds up in a battery, it's either going to leak out slowly or build up and leak out all at once. Very much not an equal comparison.
    - adrian_b 7mo ago
      What the other poster said about the risk of releasing cyanide during overcharging is not true. Cyanide could be released only at high temperatures over 300 Celsius degrees. During a fire, there are many other things in a car that can release toxic fumes easier than a sealed battery.
    - wat10000 7mo ago
      The methane is almost always piped in to be burned, and that can easily create odorless carbon monoxide. And the smell is not foolproof either. This does routinely kill people and we keep doing it. The jurisdictions that are banning it are doing so because of environmental reasons, not safety.
- adrian_b 7mo ago
  Batteries with Prussian blue cannot kill people silently. Cyanide could be released only at high temperatures, e.g. if the battery is opened and burned, not during normal operation, even if overcharging is not prevented, as it should. The sulfuric acid from the traditional lead-acid car batteries is more dangerous than this.
UncleOxidant 7mo ago
Or you could just have the batteries in a separate enclosure away from your house. I think I would be inclined to do this anyway, certainly for Lithium batteries given the possibility of fire.

deleted 7mo ago

[deleted]

hunterpayne 7mo ago

Its metallic sodium. Its about 30 times more volatile than Lithium. We don't use metallic sodium for almost anything industrial because of this volatility. I assumed there would be some mixed Li-Na-ion batteries. A pure Na-ion battery is an explosive waiting to go off. Putting these in a car...seems rather like a poor choice unless you are a personal injury lawyer.

mlsu 7mo ago
This is incredibly misleading. It's not like there's a bunch of metallic sodium sitting in the battery waiting to react. It's a lot closer to a solid solution. Do you have a personal injury lawyer on speed dial for your table salt?
- chromacity 7mo ago
  Your response is even more misleading than the misconception you're trying to correct. The complexes formed in (charged) lithium batteries are unstable and reactive in ways quite similar to the base metal. The salt molecule, in contrast, is pretty unreactive. Salt shakers don't catch fire if dropped.
  - adrian_b 7mo ago
    Which complexes are reactive? The substances similar with Prussian blue are very stable. During charge and discharge, the ionic charge of iron ions varies between +2 and +3 and the structure of the electrode has spaces that are empty when the charge of the iron ions is +3 and they are filled with sodium ions when the charge of the iron ions is +2. Both states of the electrode are very stable, being neutral salts. The composition of the electrolyte does not vary depending on the state of charge of the battery and it is also stable. The only part of the battery that can be unstable is the other electrode, which stores neutral atoms of sodium intercalated in some porous material. If you take a fully charged battery, you cut it and you extract the electrode with sodium atoms, that electrode would react with water, but at a lower speed than pure sodium, so it is not clear how dangerous such an electrode would be in comparison with the similar lithium electrodes.

adrian_b 7mo ago

Do you have any link for the claim that overcharging can produce cyanide? I have never heard such a thing and all the articles that I have seen about overcharging concluded that such batteries are much safer during overcharging than other kinds of batteries, the worst case effect being battery swelling. In normal conditions, even during overcharging there are no obvious chemical reactions that could produce hydrogen cyanide. For instance, at https://pubs.acs.org/doi/10.1021/acsenergylett.4c02915 https://pubs.acs.org/doi/10.1021/acsenergylett.4c02915 it is said that cyanide release can happen only at temperatures above 300 Celsius degrees. Such temperatures cannot be reached in normal conditions.

MengerSponge 7mo ago
> Such temperatures cannot be reached in normal conditions Thank you for the reasonable chuckle I got from this understatement of the day.
- adrian_b 7mo ago
  By normal conditions I mean charging and discharging and even overcharging if the controller is defective. Burning the battery is something that I define as not normal conditions. Many plastics produce toxic fumes when burnt and many such plastics may be used in a car. Burning the battery is not the greatest risk of toxic fumes during a fire. If the fire is intense enough, any released cyanide might also be burned.
  - WarmWash 7mo ago
    The battery heats itself in these failure modes.
    - adrian_b 7mo ago
      Not to 300 Celsius degrees. A battery of any kind can overheat with the output shorted or during excessive overcharging, but normally whenever a battery is used in a device there are protective devices that prevent such events. If there are no protections, the designer is guilty, not the battery. Moreover, such risks are greater for Li-ion batteries, which have flammable electrolyte. Na-ion batteries will replace Li-ion only in certain applications, like stationary energy storage, cars for cold climates and cheaper cars, while Li-ion will remain the choice for maximum energy per kilogram. But it is weird to be concerned about the safety of Na-ion when that is certainly not worse than for Li-ion and most likely it is better.

Toutouxc 7mo ago

Just adding to what others have already said — overcharging the cells is not something you're supposed to be doing. Overcharging even today's common Li-ion cells, i.e. those in your phone, vacuum, EV or home storage, will lead to comparably spectacular results.