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Batteries don't need to hit theoretical maximums, they only need to get within the ballpark of liquid fuels (maybe .25-.5x)? This will basically require the use of air in the reaction, since one of the reasons liquid fuel can store so much energy in such a compact and lightweight form is that it doesn't require storage of one of the primary reactants (oxygen).

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last time i check liquid fuel has 50x the energy density of battery.

so to get to /4, you would need a 12x increase.

>since one of the reasons liquid fuel can store so much energy in such a compact and lightweight form is that it doesn't require storage of one of the primary reactants (oxygen).

the main reason is the covalent bond is stronger. using air will only double the energy density for fuel( 1x fuel instead of /2 fuel /2 oxygen.)

Hydrogen is a lot lighter than Oxygen, so you can increase the density a lot more than by a factor of 2.

Also important in some applications, such as aerospace, is that liquid fuel depletes in weight as you use it. Batteries are enough of a closed system that you still have to carry all of the weight around even when you're out of power.

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