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.

While this article is about cars, there is another Chinese company that offers 50 MWh sodium-ion batteries for stationary energy storage.

While for cars sodium-ion batteries will never reach the energy per kilogram of the best lithium-ion batteries, for stationary use it makes absolutely no sense to use lithium batteries, because sodium batteries will become much cheaper when their production will be more mature, so they should always be preferred to lithium batteries.

Even for cars, sodium-ion batteries have a second advantage besides price, they retain their capacity and their charging speed down to much lower temperatures than lithium-ion batteries, so they will be preferred in cold climates.

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.

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.

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.

The sodium-ion batteries are said to work satisfactorily down to -40 Celsius = -40 Fahrenheit.

-20 Celsius just happens to be a temperature for which a retention ratio was specified in the parent article, and not the limit of the operation range.

Actually a few other HN threads have just discussed the latest Chinese electric cars that refuel in 5 minutes for a 250 miles range and which have a 500 miles range when fully charged.

That makes fast, long-range travel quite practical in an electric vehicle.

While this model greatly improves the charging speed, other electric cars introduced this year use sodium-ion batteries, which are heavier than lithium-ion batteries, but they have the advantage that in cold climates they do not lose either capacity or charging speed down to temperatures as low as minus 40 Celsius degrees, removing other limitation of electric cars.

So hydrocarbon fuels are likely to remain non-replaceable only in aircraft and spacecraft, where weight really matters.

However, hydrocarbon fuels can be synthesized from water and carbon dioxide, passing through syngas, by using solar energy, just not at a price competitive with fossil fuel.

The RC-5 cipher was very nice for its day, but I am certain that it is much slower than AES on any modern CPU, with the exception of microcontrollers, where nonetheless other solutions, e.g. ChaCha20, may be faster.

AES also needs only a handful of lines of code for its implementation (using assembly). For such an application, you can even reduce the number of rounds of AES-128, e.g. from 10 to 4.

When you want truly uniform random numbers, then encrypting with AES-128, then truncating, is best. If you want invertible encryption, then you should encrypt a counter and either use a 32-bit addition or a 32-bit XOR for encrypting the 32-bit number. With a single AES-128 invocation for generating a random mask, you can encrypt four 32-bit numbers.

Of course, when speed does not matter, you can use pretty much any of the historical block ciphers, because the security requirements for encrypting 32-bit numbers are very low, since they are easier to find by brute force searching than by attempting to break any kind of encryption.