"Lithium-ion" and "Lion" are just generic terms for all battery chemistries where the mobile ion moving between anode and cathode is lithium. There are at least 18 different battery chemistries of this type, only a small number of which are in production. I think the Leaf uses LiFePO4 and the Volt uses a different chemistry with Mg which has a bit higher energy density but which is also more temperature sensitive, hence the requirement for better temperature control of the battery pack on the Volt. Toyota has been the laggard on ev development, despite being the first to market with a hybrid. They have stuck with nickel metal hydrid batteries on the hybrid, but I think the PHEV models will use a lithium based chemistry. It seems to me that NiCad is used mostly on trucks where weight isn't quite as much a concern (but is being displaced by lithium), and older ev's. The infamous laptop pc batteries which can catch fire under certain circumstances are a lithium cobalt chemistry. There are also lithium polymer cells made for example by Kokam, which have higher specific energy than the other lithium cells, but shorter cycle life and much higher cost. Most on this forum use the LiFePO4 chemistry since they are available at relatively low cost from China as so-called large format or prismatic cells. A U.S. company, A123, makes smaller cells with this chemistry, but they are higher power than the prismatic cells due to different fabrication technology, and more expensive. So you can see that referring to all lithium chemistry cells by some generic term as if they were all the same is misleading.