That overhyped Na-Cl₂ battery

News: new battery could mean six times the range in an electric car! 🙌

Press release: six times the electrode capacity compared to lithium-ion batteries 👍

Paper (in Nature): …normalised to the mass of a carbon coating on a Ni foam electrode 🤔

Don’t get me wrong, I find the chemistry interesting, but this is a good example of misleading scicomm starting with questionable reporting in the paper itself. The <5 mg/cm² carbon isn’t the active material, the ~150 mg/cm² SOCl₂/AlCl₃ electrolyte is…

If we want to compare this fairly, it should be done on the basis of actual redox active materials. However, even assuming Cl₂ as the active material, theoretically this is ~760 mAh/g(Cl₂)

Excerpt from the news article

And it’s not that this not-very-appropriate comparison is just in the press release, it’s heavily implied in the SI too. I’m surprised to find this Nature of all places (or perhaps I shouldn’t be) - we have known this is not a fair practice since at least the Li-air heyday.

Table from the Nature paper

Maybe it can be argued that because the active material is actually liquid/dissolved it is hard to compare on the same basis. In which case maybe a comparison of mAh/cm³ would be better… but if only I could find the thickness of the Ni foam…

I could get a little cynical about the practical prospects or whether it can be fairly called a Na/Cl₂ battery at all but I won’t. I’ll rather just encourage researchers, reviewers, editors to be a bit more careful about reporting numbers like these…