Unfortunately not, with current technology the efficiency of dynamos and motors is only in the 80-90% range, such a system could only convert 80% of the energy you put into pedaling into motion.
On the other hand, if you simply used this energy to propel the bike, you can put almost 100% of that energy into motion. Put simply, the bike is simpler and will go further without this system. With that in mind just using a lower pedal assist mode will use less of the motor's energy and thus allow you to go further on your own steam!