I’ve ranted about this one before. From a New York Times article on battery capacity:
Methanol-based microcells, for instance, have roughly 10 times the energy density, creating the prospect of wireless laptops that could run all day without recharging, according to Rick Cooper, vice president for business development of PolyFuel Inc. The company, based in Mountain View, Calif., supplies components to several Asian manufacturers that have been working on such devices.
“The energy capacity of batteries is increasing 5 percent to 8 percent annually, but demand is increasing exponentially,” Mr. Cooper said.
5 percent growth per year is exponential growth.