Battery power duration and energy levels are one dimension of limits on portable devices. There appears to be a lot of upside in this area.

“Despite their high energy density, lithium batter-ies are not used in cars

and other transportation applications because they cannot deliver power at

a sufficiently high rate. Kang et al. (p. 977) report a combined

theoretical and experimental exploration of a class of battery electrodes

with a layered transition-metal structure that permits much faster lithium

ion transport. The results suggest a general strategy for improving

lithium-battery power delivery.”

http://www.sciencemag.org/content/vol311/issue5763/twis.dtl#311/5763/913d