Better batteries are on the way. Materials scientist Shirley Meng of the University of California, San Diego is part of the Battery 500 Consortium working on new battery designs.

Commercial lithium-ion batteries can store about 250 watt-hours of electricity per kilogram, she said, but new designs could double that in a few years – although it depends on how quickly factories can be equipped to make them.

"We don't have mass production capabilities, but on the research front, right now we are hitting 400 [watt-hours]. We're not at 500 yet," Meng said.

https://energystorage.pnnl.gov/battery500.asp