Liquid nitrogen does an even better job. Being considerably denser than liquid air, it can store more energy per unit volume, allowing cars to travel further on a tankful of the stuff. Weight for weight, liquid nitrogen packs much the same energy as the lithium-ion batteries used in laptops, mobile phones and electric cars. The big difference is that a liquid-nitrogen car is likely to be considerably cheaper to build than an electric vehicle.

It's not a terrible idea -- but it's not a new idea.

From 15 years ago: http://www.washington.edu/alumni/columns/dec97/car3.html