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.

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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.

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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.

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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.