Hello! I was wondering what you would call the opposite of a freewheel hub motor? I am interested in a motor which can not only accelerate an electrical vehicle, but also provide the breaking power.

Thank you.

It's called a generator, and the system is called regenerative braking. Some modern hybrid and all-electric vehicles do this - they connect a generator into the brake system to create electricity as it slows the car. Both Prius and Tesla do this - i'm sure there are others.