Spectrum: "…its energy density will need to be improved, the researchers say.""Anyway, the article carefully avoids talking about energy density. Which is of course the key thing here."
I agree. And as you say, there's a bit of inaccuracy in the article. In fact, it's more than just a little—not to mention the omissions.
What's so annoying about this article is that it's from the IEEE's magazine Spectrum where one expects the best—the most authorative, factual and most current—technical information available at publication time but it's often not the case.
Unfortunately, in recent years, the IEEE has been unduely influenced by commercial interests which has affected or slanted the accuracy of its reporting of science and engineering news. As Spectrum is the main face of the organization and its principal news outlet this is where the policy shift has been most obvious.
I could give other instances of bad or overly enthusiastic reporting of new tech where known downsides were either not reported and or downplayed but I'll refrain here as I don't have the issues of Spectrum immediately to hand to give specific references. Suffice to say, I became so disillusioned with stuff I was reading in Spectrum† that I terminated my 20-year-plus IEEE membership some while back.
My main criticism of this story is—as you correctly point out—carefully avoids talking about energy density, which has to be a crucial aspect of any story about new battery tech that's posited as a potential competitor and or replacement for Li-ion. That's damn obvious. If the researchers did not provide numerical comparisons (experimental and or theoretical) of the energy densities between their Al-ion prototypes and Li-ion in their paper/press release then Spectrum's editor should have provided a side/footnote on the matter.
Most of us already know that Li has a larger electrode potential‡ than Al, so Al is already coming from behind Li in this regard, but of course that's far from the end of the story as there are many other factors involved in addition to those benefits as promulgated by the researchers, namely recharge cycles, safety and cost. For example, how does Al stack up against Li as far as electrode surface area (spongy metal surfaces, etc.)? We know from long experience with electrolytic capacitors that Al can be treated to have very large effective surface areas, in fact they can be enormous. If Al has the potential to be much better than Li in this regard then this new tech could certainly be a winner. As this is an obvious factor, Spectrum's editor should have mentioned it amongst others even if not mentioned in the original paper (in fact, Spectrum should have criticized its omission if the case).
In summary, one would hope this research leads to much better and safer batteries but the IEEE—as the premier representative for electrical and electronic engineering/engineers—has done precious little in providing us with information that actually matters.
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† Whilst I've strong criticisms of the IEEE not all are negative, many of its specialist publications are quite excellent including Proceedings of the IEEE.
‡ From Wiki: Standard electrode potentials:
Li: Li+ + e− ⇌ Li(s) -3.0401V
Al: Al3+ + 3e− ⇌ Al(s) -1.662V
Edit: It was only after I'd written this comment that I was able access the original ACS research paper (initially I'd difficulty downloading it). I've since skimmed it several times and I need to read it thoroughly to get a proper understanding but it's pretty short on the issues I've raised. Thus, my point that Spectrum should have mentioned these shortfalls still stands.