Lithium Air One materials scientist told me that lithium air is the "grand slam home run" of energy density. Lithium-air batteries differ from lithium-ion batteries in that they use carbon for their positive electrode instead of metal oxides. Carbon is lighter and reacts with oxygen in the surrounding air to produce electrical current. Although it promises a 1,000-mile range instead of just 125 miles for electric vehicles, lithium air batteries have also proven to be unstable. The big problem is that lithium ignites when it contacts moist air. But IBM researchers in California and Switzerland reported this month that they have solved a key problem in the battery’s electrochemistry by finding a different kind of electrolyte solution. IBM hopes to have a prototype lithium-air battery by 2013. Startups like Berkeley-based PolyPlus are also hunting for this "holy grail" of battery tech. Critics say that lithium-air research has been underway for two decades without complete success.