| ▲ | WarmWash 12 hours ago |
| 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. |
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| ▲ | adrian_b 10 hours ago | parent | next [-] |
| 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 it is said that cyanide release can happen only at temperatures above 300 Celsius degrees. Such temperatures cannot be reached in normal conditions. |
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| ▲ | WarmWash 8 hours ago | parent | next [-] | | Sure https://chemistry-europe.onlinelibrary.wiley.com/doi/full/10... https://www.sciencedirect.com/science/article/pii/S2352152X2... https://pubs.acs.org/doi/10.1021/acsenergylett.5c02345 Also understand, nothing bad happens under normal conditions. It's when the cell goes awry that bad things happen. 300C is easily obtainable by a runaway cell. I mean, short two ends of the battery together with a thin foil and see how quickly it hits 300C... Also I'm not trying to fear monger, battery failures are very rare. But SIBs aren't totally free of scary failure modes. | | |
| ▲ | adrian_b 6 hours ago | parent | next [-] | | Your links do not describe any problem that is inherent in the principle of such batteries. They only warn against the danger of not taking care during fabrication to eliminate the moisture from the electrode. If such low quality electrodes are made, they are prone to decomposition at lower temperatures than the well made electrodes, which have been dried sufficiently. Similar risks of bad fabrication exist for any kind of batteries, like there were a few notorious cases of lithium-ion battery models that were prone to catch fire. Moreover, in most applications of such batteries one must use short-circuit protections, so it should be impossible to overheat a battery by shorting its outputs. If that happens, not the battery is guilty, but whoever has designed a device without protections. The point is that absolutely any kind of battery presents risks. Without short-circuit protections, any battery could cause a fire when shorted. There is no reason to believe that sodium-ion batteries are less safe than lithium-ion batteries. On the contrary, it is very likely that sodium-ion batteries are safer, e.g. for not having a flammable electrolyte. | | |
| ▲ | WarmWash 5 hours ago | parent [-] | | I'm sorry, do you actually know about batteries, or do you just casually read about them and now feel obligated to defend a point you tried to make? The shorting which causes failure is internal, from manufacturing defects. Yes, it's rare. No, it's not something the end user can detect or short protection can stop. This is pretty basic knowledge...hence my questioning (and you totally wooshing on the foil shorting demonstration I pointed out...batteries internally use foil, the foil is what gets hot). So you have to decide if you want your possible but very rare event to be a small fire or a hydrogen cyanide gas leak. Also SIBs are a new tech, so who knows what the failure rate will actually look like. Or if CN will even be a concern, the chemistry for mainstream cells might be different. |
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| ▲ | SirHumphrey an hour ago | parent | prev [-] | | I think it’s more that when you have 300C thermal runaway in a cell in your battery storage bank the release of toxic compounds is the least of your problems. I work quite a bit with batteries and the fear of battery fires hunts me in my sleep, especially with lipos. |
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| ▲ | MengerSponge 10 hours ago | parent | prev [-] | | > Such temperatures cannot be reached in normal conditions Thank you for the reasonable chuckle I got from this understatement of the day. | | |
| ▲ | adrian_b 9 hours ago | parent [-] | | 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 8 hours ago | parent [-] | | The battery heats itself in these failure modes. | | |
| ▲ | adrian_b 6 hours ago | parent [-] | | 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. |
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| ▲ | Toutouxc 37 minutes ago | parent | prev | next [-] |
| 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. |
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| ▲ | 11 hours ago | parent | prev | next [-] |
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| ▲ | cyberax 12 hours ago | parent | prev | next [-] |
| 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. |
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| ▲ | UncleOxidant 11 hours ago | parent | next [-] | | 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. | |
| ▲ | devwastaken 11 hours ago | parent | prev [-] | | 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. | | |
| ▲ | adrian_b 10 hours ago | parent | next [-] | | 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. | |
| ▲ | wat10000 11 hours ago | parent | prev | next [-] | | 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 11 hours ago | parent [-] | | 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 10 hours ago | parent | next [-] | | 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 9 hours ago | parent | prev [-] | | 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. |
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| ▲ | cyberax 11 hours ago | parent | prev [-] | | > 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? | | |
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| ▲ | hunterpayne 11 hours ago | parent | prev [-] |
| 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. |
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| ▲ | adrian_b 10 hours ago | parent | next [-] | | I doubt that it is metallic sodium, for the same reason why the rechargeable lithium batteries do not use metallic lithium electrodes like the non-rechargeable batteries. During charge-recharge cycles, a metallic electrode is likely to be degraded quickly. So it is more likely that the reduced sodium atoms are intercalated in some porous electrode, e.g. of carbon, while at the other electrode the sodium ions are intercalated in some substance similar to Prussian blue. The volatility of sodium does not matter, because it is not in contact with air or another gas, but only with electrolyte. | |
| ▲ | mlsu 10 hours ago | parent | prev [-] | | 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 10 hours ago | parent [-] | | 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 9 hours ago | parent [-] | | 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. | | |
| ▲ | hunterpayne 9 hours ago | parent [-] | | Fine, now show a video of what happens if you pierce the Na-ion cell with something metallic. Because explosion doesn't even begin to cover what happens next in that situation. And you are suggesting that everyone should be 2 ft from such a cell, traveling at 60 mph, in all weather conditions. These things should be restricted to grid stabilization batteries and nothing else and you know it. Don't mislead people on such things. | | |
| ▲ | adrian_b 9 hours ago | parent [-] | | Piercing a Na-ion cell is not good, but the effect is pretty much the same like piercing a Li-ion cell. In both cells the electrode that stores alkaline metal atoms has high reactivity, but in both cases the reactivity is much smaller than for a compact piece of metal, so the reaction with substances like water would proceed much more slowly than in the movies when someone throws an alkaline metal in water. If you pierce the cell, but the electrode does not come in contact with something like water or like your hand, nothing much happens, the air would oxidize the metal, but that cannot lead to explosions or other violent reactions. The electrolyte of lithium-ion batteries is an organic solvent that is very easily flammable if you pierce the battery. The electrolyte of sodium-ion batteries is likely to be water-based, which is safer, because such an electrolyte is not flammable. It would be caustic, but the same is true for any alkaline or acid battery, which have already been used for a couple of centuries without problems. Overall, sodium-ion batteries should be safer than lithium-ion batteries, so safety is certainly something that cannot be hold against them. |
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