Paul, I believe that manganese is preferred over cobalt because it can assume more "valence" states, this allow use of a smaller volume of the lithium manganese spinel (presumptive, since I do not know for sure that is what they are doing, but that is what I would have done), as well as more (probablt) charging and discharging. However, it is indeed more difficult to get reproducible compositions of the Li-Mn mixed oxides. I have no doubt that the Mn versions have advantages over the Co, but the Co are pretty good.
As for environmental effects, since the cobalt is in the oxide form, I really do not know what is the fuss, unless we are going to ban the existence of cobalt based minerals which are also in the oxide form. I do not know if Mn is more acceptable. Cobalt based alloys have been used for many years, and the metallic form would be more hazardous then the oxide form. Co is also less "toxic" than chromium, and there is a lot of chromium going into stainless steels, which I do not foresee being an environmental problem soon.
Zeev |
