Yes that is a very good point, it would be especially significant when thinking about electric cars where power to weight ratio is vital.
Thanks for the information, your point about weight and energy is especially crucial when talking about electric cars where power-weight ratio is so important. I think the recovery of lithium from spent cells has to be near 100% for electric cars to be a permanent alternative, do you know of any sources that go into detail on lithium extraction from used batteries?