Green Energy

it would (as far as i understand with high school chemistry) be strictly more efficient to electrolyse rust directly

I'm not a chemist either, but I do know a bit of chemistry.

Typically, you need a solution of NaOH (sodium hydroxide) to directly reduce iron oxide in an electrolysis cell. If your iron oxide contains impurities, those may react with NaOH and ruin the fun. Also, if you have exposure to CO2, your NaOH will gradually degrade, producing NaHCO3 and losing potency.

My impression: wet electrolysis is great for making high purity iron, but it would be hard to make it work for energy storage.