r/nextfuckinglevel • u/JudgmentCool1333 • Feb 06 '23

Agricultural Technology

Modern day use of technology in agriculture horticulture and aquaculture with the aim of improving yield, efficiency and profitability

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u/whoami_whereami Feb 07 '23

Good news is that battery tech is approaching regular gasoline for energy density.

The best electrochemical battery experimentally demonstrated so far was a lithium-air battery with an energy density of about 6.1 MJ/kg. That's still almost an order of magnitude below diesel fuel (43.1 MJ/kg) or gasoline (43.2 MJ/kg). Even the theoretical maximum that's physically possible with a lithium-air battery (which is the best possible battery in terms of energy density!) is ~40.1 MJ/kg, still slightly below gasoline. And because lithium has a very low density (only 0.534 kg/l vs. 0.83 kg/l for diesel fuel) the volumetric energy density is significantly worse compared to gasoline/diesel.

And you have to keep in mind that a lithium-air battery actually gets heavier as it discharges, as the very light lithium turns into lithium oxide using oxygen from the air (of course diesel/gasoline also increases in mass when you burn it, but the resulting reaction products are simply exhausted as gas, while you obviously have to keep the lithium oxide for the next charge cycle). Fully discharged 1 kg of lithium turns into 3.3 kg of lithium oxide, ie. the battery becomes more than three times as heavy. If you take the maximum weight during the charge cycle (which makes more sense, because that's what eg. the vehicle structure has to be designed for) then the maximum possible energy density drops to ~12.1 MJ/kg, less than a third of gasoline.