this post was submitted on 09 Jan 2024
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Ok, I am interested in anyone with specific knowledge on this topic indicating whether the first order mental image I have of battery tech is correct?
The way I understand it is that the highest energy density batteries are your non-rechargeable lithium cells like watch batteries. Rechargeable lithium-ion cells have perhaps half the capacity due to the fact that they need to add measures that prevent these dendrites, as mentioned in the article, from forming. So the Holy Grail here is to develop a rechargeable technology that prevents the dendrite problem without sacrificing capacity so that you can get the best of both worlds? And that is what they are working on here with the solid state design. Am I close to the mark?
I'd say the "holy grail" is to move away from lithium entirely and instead move towards capacitors or hydrogen fuel cells. Both are far more promising, however right now they're quite expensive and heavy.
In the case of capacitors, essentially you have two pieces of metal very close together. The closer they are together without touching the more energy you can store (the size of the metal pieces also matters - larger being better). Capacitors are old well understood technology, and in a laboratory setting you can make ones that are far better than a lithium battery. Getting that out of a lab and into mass production is more difficult and the best we have right now are quite heavy for the amount of power they store. Still, they do exist, and they work very well. A lot of electric trains, for example, will charge a capacitor when the train slows down for a station, take on a bit more charge while stopped at the station, then use most of the energy to accelerate up to speed. They might also get a bit more charge from overhead wires while travelling down the tracks.
In theory, a capacitor can charge or discharge instantly. In practice providing that much charge isn't really practical, so it's easier to charge them a little more slowly... but still way way faster than a lithium ion battery which wouldn't even be able to do regenerative braking on something as heavy as a train - that's just far too much power coming in.
Hydrogen is actually technically very light. Just 1kg (about 2lbs) is about the equivalent of the battery in a lot of EVs. However the equipment to convert that energy into motion at the wheels tends to be quite heavy and expensive. Costs are coming down however, and the Japanese manufacturers (Toyota/etc) seem to think it's the right way to go. Time will tell if they're right... but it seems like right now the biggest problem with those is just that there's nowhere to buy hydrogen - compared to an EV which you can charge pretty much anywhere. Even in your own home. There are also prototype hydrogen aircraft. Something lithium will never be able to do.
My prediction is capacitors and hydrogen will both eventually displace lithium batteries. It's more a question of when than if... I wouldn't hold your breath though.
Ok, so we're onto capacitors and fuel cells now. Here we go with my mental image of those.
On the pros side, capacitors can charge/discharge in an instant, have nearly perfect energy recovery (almost everything you put in comes back out), and have almost limitless charging cycles with no memory effects or any of that nonsense. On the cons side, even a supercapacitor can't match battery tech for energy storage density and they tend to be not so great for long-term electrical storage.
Fuel cells are sort of the opposite. Once you've sorted out the challenges in producing/storing/transporting hydrogen (these are all non-trivial but not necessarily deal-breakers either?), you're looking at essentially limitless storage duration since it's, well, a fuel. Like you can stockpile it for next year. The energy density is enviably high, though with pure hydrogen, you're doing better by weight than by volume. In any case though, it's looking pretty good compared to batteries.
But pulling the energy out of them in a timely manner is a major pain. You need either a chemical or thermal catalyst to speed it along for most applications. And the chemical of choice is platinum, which is not exactly abundant. If you wanted a fuel cell in every car, is there even enough on Earth for that? I'm not so sure.
Also, I have read impurities in the fuel can really mess up this type of fuel cell. The thermal type is purportedly more forgiving in this respect, though I picture thermal fuel cells as these hulking things that would work best as stationary power plants? Well, maybe they would be a good fit for large ships? It's hard to picture some giant container vessel plying the oceans on battery power, at any rate.