Lithium-air batteries (an immature technology, certainly) have an energy per gram 3.5 times less than gasoline's. But electric motors are about 3.5 times more efficient than internal combustion engines. And the technology to produce synthetic fuels from CO2 is pretty much as far from mass scale as lithium-air batteries.

I agree that we will need carbon-based fuels for jet engines, but as for cars, the physics and economics are by no means as favorable as you represent.