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Comment by TSiege | Hacker News Reader

Does anyone know if there is a theoretical limit for how energy dense a battery could be?

I wonder if there is a possible future where some sort of commercial long haul flights could be done by a fully electric plane. I've never gotten a great answer on this, and maybe we don't have an answer for certain since battery chemistry is some sense is still early days

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Lithium air batteries theoretically can reach 10000-12000w/kg though they have only reached 1200w in labs so far. Gasoline is 13000w/kg. We don't need to match gasoline as it is inefficient. CATL just got it's 500w/kg batteries for commercial aviation approved I am betting China is going to do the same with electric planes that it did with cars. They can't build a efficient enough jet engine to be competitive yet but they already can build the narrow body planes replace the jet engine with electric take over the market for short haul aviation once the battery densities cross 1000w/hr.

Where does 12kw/kg come from? A specific type of battery? That sounds like the energy density for lithium alone. There may be architectures like flow batteries which could get close for some chemistries, but a standard battery (intercalation of ions) cannot get remotely close, even in theory.

This was claimed by CATL chief battery scientist recently or at least that's what the press claimed could be mistranslation from Chinese to English.

As far as I could glean from the internet, it's a theoretical limit for lithium, rather than for a lithium-air battery. Any future device that gets close to that limit won't be a battery as we know it.

okay but anyway for electric commercial aviation 1000-1200w/kg would be enough to replace 70-80% of all flights.

From what I remember on the topic, batteries are not yet remotely close to dense enough to enable long haul flights. Even hydrogen electric doesn't cut it, and hydrogen fuel is much denser energy wise than conventional batteries.

Perhaps if solid state batteries become cost effective to produce at scale that would change the feasibility, but someone else would have to chime in there.

The answer to this question depends heavily on your definition of "battery".

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