Comment by qayxc | Hacker News Reader

Comment by qayxc | Hacker News Reader

While the research itself sound promising, the article leaves a lot to be desired.

The use of units and their notation is horrendous, almost as if the author doesn't know even the first thing about SI units and their use:

> 197 mAh g−1

> 10 gigaWatt to 50gW plants

I'm sorry, but nonsense like that detracts from the trustworthiness of the content.

The title is also a bit click-baity - so far they're working with coin cells and statements like

> It charges an iPhone coin cell in less than 10 seconds.

are highly misleading. What does that even mean? An iPhone doesn't contain coin cells.

Another irritating statements follows immediately after:

> The new battery cells are claimed to deliver far more energy density than current lithium-ion batteries, without the cooling, heating or rare-earth problems they face.

According to them, their cells achieve 160 Wh/kg. That doesn't add up at all. A mainstream APN 616-0809 Li-Ion battery pack (iPhone 6) has a capacity of 1810 mAh @ 3.8V and weighs ~45.5 g, e.g. ~150 Wh/kg.

So their current cells are no better than current Li-Ion batteries, but only just match them. I mean, heck, a Tesla Powerwall - a fully integrated, plug-and-play unit - comes in at 114 Wh/kg (13.5 kWh @ 114 kg) [0].

If they have a product with unique selling points (no rare earths required, much faster to charge, safer), why make claims that are demonstrably false? Little things like that make the whole announcement sound fishy and I can't tell whether it's the author or the researchers who messed up there.

I mean, seriously, the COTS Panasonic NCR18650B cell has an energy density of 252 Wh/kg [1] so even with cooling/heating elements a battery pack would have a higher energy density (by mass) than their product.

Something just doesn't add up in this piece.

[0] https://www.tesla.com/sites/default/files/pdfs/powerwall/Pow...

[1] https://www.batteryjunction.com/panasonic-ncr18650b-3400.htm...

Also, this statement is very strange:

> Testing by peer-reviewed specialist publication Advanced Functional Materials publication concluded the cells had “outstanding high-rate performance (149 mAh g−1 at 5 A g−1), surpassing all previously reported AIB cathode materials”.

Advanced Functional Materials is just a journal. They do not do third-party testing (unless something really has changed in scientific publishing in that last few years). Just because your paper was accepted for publication doesn't mean you can go around claiming your device performance has been validated by outside investigators. The peer-reviewers for journals just look at the data/figures submitted and make a judgement call on if it looks legit/plausible or if it looks fake/wrong. They don't actually get devices from the authors and test them out in their own labs to verify things...

For third party verification you need to pay outside consultants (e.g. Exponent) to test your devices or need to get a national lab like NREL to test things.

The use of ampere-hours per gram and derived measurements is extremely common in battery research. For example:

https://www.nature.com/articles/nature14340 https://pubs.acs.org/doi/abs/10.1021/jacs.5b06809 https://www.nature.com/articles/s41560-017-0014-y

I'm not referring to using Amp-hours - note that I quoted capacities of competing products using the same unit.

What grinds my gears is copy-pasting without understanding the notation. mAh g-1 is not a unit. mA⋅h⋅g<sup>-1</sup> or mA⋅h/g is. I expect a technical article to at least use the correct notation for SI units. If your publishing system is so crappy that it doesn't support middle-dots and proper superscript, use division instead.

The mess seen in the article is the result of mindless copypasta.

Nonsense like "gigaWatts" shouldn't even be possible and causes red squiggly lines even while typing this in a browser; not to mention "gW" (grams times Watts?, Wattgrams?).

If you present technical information and include technical data, use the correct notation. Failing to do so demonstrates that there's no or a very poor editorial process and that the author has no clue what they're even writing about. This doesn't inspire confidence in the actual substance of the article, much like proper grammar and orthography are an essential part of a good essay.

Yeah, I think the article misleads that these are close to parity with Li batteries not exceeding, if not slightly trailing in density. Other articles on the same batteries with quotes directly from the researchers are more clear about it.

mAh g-1 is very simple to understand. It is common notation to put a -1 exponent to indicate division.

Work to calculate the energy density comparison when that isn't even the point of the article. Everyone can look up the energey density and theoretical of a li-ion battery: 100-265 Wh/kg. There is absolutely no need to calculate anything.

Focus on the substance of the article. 60x faster charging rate as compared to Lithium-ion and make a comment regarding that. Otherwise your comments are as pointless as my reply to it.

The problem with the article is that it lacks substance. As an example, it mentions that al-ion has intrinsic advantages and disadvantages compared to li-ion, but it only talks about advantages.

Aluminum-ion technology has intrinsic advantages and disadvantages over the preeminent lithium-ion battery technology being used in almost every EV today.

What do calendar and cycle life in different conditions look like? How do weight/volume per unit power/energy compare with existing li-ion cells? And so on...

It seems like they found a way to improve the energy density of the al-ion cells mentioned in this Stanford news story.

https://news.stanford.edu/2015/04/06/aluminum-ion-battery-03...

But without more detailed specs, it's impossible to compare their cells to existing li-ion cells outside of the specific examples they are using.

> It is common notation to put a -1 exponent to indicate division.

I have zero issues with using negative exponents, what I do take issue with is writing "g-1" in an online publication. You either use proper HTML to write an exponent as an exponent, or you use division.

"g-1" is not a a unit, it spells out "gram - 1", which makes no sense at all and there's zero excuse for not even using the commonly accepted crutch "g^-1".

My laptop battery charges under a minute, but that doesn't make it any good.

If you have no issues with the units / expressions used in the article, could you please explain what is the power and energy density from this quote:

> Stanford’s natural graphite aluminum-ion technology delivers 68.7 Watt-hours per kilogram and 41.2 Watts per kilogram, while its graphite-foam bumps up to 3000Wh/kg.

> The GMG-UQ battery heaves that forward to between 150 and 160Wh/kg and 7000Wh/kg.

It is a coin battery and the Apple AirTag uses a CR2032. It was probably a simple misquote.

And yet, CR2032 batteries are not rechargeable, so it doesn't make a good misquote either.

ML2032, VL2032 and LIR2032 are similarly sized variants that can be recharged, but they're not the same, and you shouldn't attempt to recharge a CR2032.

it seems the claim about greater energy density in a vehicle sized battery is to do with saving on the cooling circuitry (20% of the battery as per the article).

That would make sense only if Li-Ion batteries didn't have power densities north of 250 W⋅h/kg.

Commercial battery cells used in vehicle sized applications, however, often do exceed this value.

So even at a 20% loss due to temperature control, an aluminium battery of the quoted power density still struggles to even just match Li-Ion batteries (i.e. Li-Ion batteries including cooling still have at least 26% higher energy density by mass; using a Panasonic cell as reference point).

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