So do you think a Sodium-based battery is safe enough, at present?
It is hard to say if sodium will be safer - it will likely just be cheaper to make. The primary fire problem is the stored energy (heat) is inside a pool of XXX carbonate which is an ignitable liquid.
I think the same (insert your trade secret brand of carbonate solvent here) will be used for the sodium ions vs lithium ions.
The chemistry is not stable for either in my opinion, but we don’t yet know because its so new we have not had a chance to test them for thermal risks.
The current flavor of the month chemistry is LFP or lithium iron phosphate. They are touted as having lower fire risks and that might be true because they withstand heat a bit better but the downside is that they can put off more ignitable vapor prior to ignition (500-6000L per kWh) so they pose a much higher risk of violent vapor cloud explosion (citing Professor Paul Christensen from the UK).
Generally once thermal runaway starts it is extremely difficult to “stop” and stopping it actually means you just break the chain reaction in the battery cells so they don’t all burn.
The sodium ion batteries will be just as toxic in my opinion as lithium ion. The upside is cost to manufacture as lithium (aka white gold) is getting more expensive. The downside for sodium from what I have heard/read is that they are lower energy density and don’t last as long but CATL in China claims they have solved this.
We will see.
link to Dr. Christensen presentation above if you want to watch him.
There is some good stuff on youtube from academics and engineers on these things.