[lukevp]

Is there a similar volumetric equivalent measurement or is it all about energy density by weight? Like, if the batteries are lightweight but massive, that would also be a bit of a problem since the structure to safely transport a large volume could be expensive and heavy.

[sn0wf1re]

Looks like the created cell is 614 Wh/L from the above comment. Gasoline is ~2.2kWh/L [0]. So my take is that even with the created cell the density is not going to be an issue with car or grid batteries -- only <4 times the size even at this non-theoretical cell. Who knows how the packs will be configured though as I am sure airflow will be a design consideration when making larger packs.

[0] This uses the 3kWh/kg that was provided above and a density of gasoline of .75g/mL

    units
    You have: 0.7429 g/mL * 3 kWh/kg
    You want: kWh/L
 * 2.2287

[adrian_b]

That 3 kWh/kg estimated by the poster above corresponds to an abysmal efficiency of an internal-combustion engine, of less than 25%.

Modern cars with good high-compression engines have efficiencies over 40%.

A fuel cell with hydrocarbons could reach efficiencies of 60% or more.

So no lithium battery can reach volumic energies or specific energies comparable to what can be achieved with hydrocarbons.

The reason to use lithium rechargeable batteries is to obtain a better total efficiency of using energy, not the hope that it is possible to match the densities achievable with energy stored in hydrocarbons.

Among lithium rechargeable batteries, the lithium-air batteries should achieve the best energy per mass, perhaps also per volume.

Usually the weak point of metal-air batteries is the power per mass or the power per volume, because the reaction with air is slow, therefore the electrical current density in the electrodes is low, so to obtain a given amount of power requires great areas for the electrodes.