I did see a video many years ago explaining how physics only allows a battery to hit a certain storage level and no more. Blimey, if a battery could have been made to store the energy that's in diesel and/or petrol, we would be daft not to go down the battery route. But as for tractors, I didn't realise it was that bad.
Care to post your source for that statement? Here is one source;
"I don't know the actual answer to this question, but I know a least upper bound to the answer, and a means of figuring out the real answer.
Battery scientists have a metric called maximum theoretical specific energy; you can read about the definition in
Advanced Batteries by Robert Huggins. Right now, the most energy dense batteries you can buy are lithium ion, which are in the 100-200 Wh/kg range. I don't know what the best battery is, but
later in the book, Huggins shows calculations that indicate that Li/CuCl2 cells have an MTSE of 1166.4 Wh/kg. (5x the capacity of current batteries!)
We know that the highest MTSE is at least 1166.4 Wh/kg; you could use his method to calculate the same value for other chemistries, but the search space is pretty large.
I've also seen references on the internet to Li/O2 and Al/O2 batteries with MTSE of 2815 and 5200 Wh/kg, respectively. Not sure how credible those references are. Later references, like
this 2008 article in the Journal of the Electrochemical Society, suggest that the MTSE for a Li/O2 cell is around 1400 Wh/kg."
This is more a physics/chemistry/nanotech question, but what's the theoretical best energy density you could get out of a chemical battery (or fuel cell), if you could arrange atoms in any manner you
electronics.stackexchange.com