The biggest drawback of batteries today is high costs, not physical parameters. A BEV with Model S range could be as popular as the Toyota Camry if it could be

The biggest drawback of batteries today is high costs, not physical parameters. A BEV with Model S range could be as popular as the Toyota Camry if it could be profitably sold for the same pre-rebate MSRP as a Camry. Tesla doesn't need to find a metal lighter than lithium; they just need to bring lithium ion costs down. For stationary energy storage energy density is even less important and costs are even more important. IMO the best way to make stationary energy storage affordable would be to increase battery cycle life, via chemistry tweaks and/or charge controller tweaks. You don't have to compete so fiercely on lowering up-front costs if you're selling to institutional customers and can demonstrate lowered lifetime costs. I'm not going to proclaim that lithium ion batteries will certainly win the storage wars. But I think there's an interesting historical example from photovoltaics. In 1976 terrestrial PV cells were mostly made out of crystalline silicon and a lot of researchers were searching for materials that could lower PV costs either by increasing conversion efficiency or by being cheaper than high purity silicon. The search never stopped, and maybe some day silicon will be overthrown. But in 2016 crystalline silicon is still the most common, most efficient, and least expensive option for making terrestrial PV cells. Iterative improvements on the incumbent technology kept it ahead of all the many disruptive alternatives proposed over the decades. Maybe the same will happen with battery chemistry (either lithium ion or another one that's already been commercialized, like sodium ion) -- iterative improvements that keep disruptors forever playing catch-up.