[telchar]

Your source seems to be low by about 2 orders of magnitude on the energy density of lithium. They assume ~100% of a battery is made of lithium. There are only 200-300g of lithium metal per kwh in a lithium ion battery[0,1], or 12-18MJ per kg.

[0] http://www.meridian-int-res.com/Projects/How_Much_Lithium_Pe... [1] https://www.researchgate.net/deref/http%3A%2F%2Fgreet.es.anl... page 10