Solid sulphur battery

1200 mah per gram - no electrolyte.

http://phys.org/news/2013-06-all-solid-sulfur-based-battery-outperforms-lithium-ion.html#ajTabs

Sorry, that would be too efficient and cost effective to allow on the open market, if it's as good as it sounds. Energy providers are companies that are "too big to fail," so their monopoly must be protected at all costs.

Seriously, though, we need technologies that are effective AND can be replicated at home in our basements and garages. That's the only way I see around suppression of potentially disruptive technologies. The ability to safely and cheaply store electricity for later use is definitely a disruptive technology.