Hey.
What are the biggest limitations on improving today’s battery technologies?
In: Technology
Batteries are very energy-dense compare to other stuff that does not use the oxygen from the air like the fuel you burn.
A rechargeable Lithium-ion battery is in the 0.4-0.9 MJ/kg range.
If you go up to 10x that you are in the energy range of explosives like TNT that is at 4.18MJ/kg The strongest stable explosives is around 1.7x the energy of TNT
A battery needs to be a device that releases energy in a relative slow and controlled way not releasing all at once like explosives that will limit the maximum energy you can have in a safe battery.
Energy is stored in chemical bonds in the battery and there is a limit of the amount you can have that is stable and safe
If you ever have seen a video of the result of a short in a lithium-ion battery you can see that they contain a lot of energy. You do not like a battery that might explode and kill you.
So do not expect an increase of batteries of the same size that last for months or weeks. That would require more energy than explosives and they only need to be made to be stable and release energy, not being rechargeable and release energy slowly.
This is as mention if you do not use atmospheric oxygen because if you do you only need to carry part of what is used with you and the will get lighter. This is why stuff your burn is so energy-dense because the majority of the mass of what you use to get out energy is atmospheric oxygen.
There are batteries that use the oxygen in the air like [Zinc–air batteries](https://en.wikipedia.org/wiki/Zinc%E2%80%93air_battery) that is common in hearing aids. The result in in a way slow-burning of zinc and the can be safe because oxygen is only slowly let into the. The energy density is around 1.6MJ/kg the drawback is they are not rechargeable. They can be stored for a very long time but when you remove the air seal and start to use them they will be used up in a fixed time. So good for hearing aids but not phones.
There us the development of a rechargeable [Lithium–air battery](https://en.wikipedia.org/wiki/Lithium%E2%80%93air_battery) you will get an energy density in in theory of 9MJ/kg in practice it will be less. So we talked about less than 10x energy density of Lithium-ion batteries perhaps 5x is a reasonable expectation. The problem is that they are experimental and the number of recharge cycles is quite low.
There is another option like fuel cells that use for example alcohol and oxidize with air. The problem is that you need the fuel as they are not rechargeable. Fuel cells are expensive and will be larger. So there are power banks that use this technology but in general, the disadvantages so the practical use case compare to batteries in the phone and an external power bank with batties is quite low
[https://en.wikipedia.org/wiki/Energy_density](https://en.wikipedia.org/wiki/Energy_density)
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