Iz, DDB - our approach is to use the best cell chemistry for the application, and we definitely shop around. We have people in the powertrain group dedicated to understanding and following all the cells that are on the market and that are coming down the pike. Cobalt cells like those in the Roadster are very high energy density which is appropriate for a pure EV. Iron Phosphate cells (such as A123) have good power and cycle qualities but have about half the energy density of the cells currently in the Roadster. Using A123 cells we would have a range of about 110 miles and moderately increased power. Lithium Titanate spinel cells (Altair) are very expensive and have less than half the energy density. A Roadster using Altair batteries today would cost about $170,000 and have a range of less than 100 miles.
Regarding EEstor, we'll believe it when we see it. If their claims are true, then we won't need batteries anymore at all. Sounds really great! They have been very opaque about their development, including when JB and others visited them in Texas. They have never produced a working prototype that I am aware of.