NiZn may offer high power / low cost option:

http://www.powermanagementdesignline.com/news/206905768

Interesting read, one thing I didn't notice was a comparison of weight to voltage output, one thing the LiON has for it is it is considerably lighter than a NiMH for the same voltage output. Also a LiON battery has a better voltage output curve.

And based ont he cart, though LiON may seem more costly to run, the advantage is the higher output.

this battery technology will be good for smaller devices and may make some differances.