With billions of dollars flowing to electric cars, investors are eagerly waiting for the next breakthrough in battery technology - one that will underpin the future adoption of green vehicles.

They may be waiting a while: The technical challenges of making better batteries (and therefore, electric vehicles) are enormous and the expectations associated with them are even more fantastical.

Such disproportionate enthusiasm is misplaced. Battery costs, which make up almost half the expense of an electric car, have come down, while their energy density has gone up, meaning vehicles can go further. Government subsidies are helping too.