Is BMW working on an electric car that could do 706 miles per gallon?

Is BMW working on an electric car that could do 706 miles per gallon? | Daily Mail Online: "It may be less than a year since BMW launched its i8 hybrid sports car, but rumours are already swirling about an even more efficient model. They claim the German automaker is developing a prototype car that can do a staggering 706 miles per imperial gallon (588 miles per US gallon)."