87
Lithium metal battery with over 500 Wh/kg developed
(www.notebookcheck.net)
This is a most excellent place for technology news and articles.
In general efficiency, modern cars are a lot closer to 40% than 20. E.g. a Prius engine is at 38,5%.
It was interesting to see F1 engines go past the 50% mark, a few years back.