It's an issue that goes beyond cars and mobile devices. To reduce carbon emissions, utilities are likely to shift more generating capacity from coal and natural gas to renewable sources like wind and solar. Solar cells and wind turbines require batteries because they provide power intermittently.

Optimists are confident that those challenges can be overcome. They envision a day when your electric car helps store the power generated by your rooftop solar panels, with many homeowners selling homegrown electricity back to the utility companies over the grid. This vision of energy nirvana sounds great to Molinaroli, who runs Johnson Controls' batte