"Because the car would still rely on its regular rechargable lithium-ion battery most of the time and would switch to the aluminum-air battery as a backup only if the lithium-ion battery ran out, and because most car trips are 50 kilometres or less, Alcoa estimates the aluminum-air batteries would only need to be changed about once a year." This is a chemical battery with very limited lifespan. Additionally without a…
In a sense it's green if they are produced from green energy, like hydroelectric power in remote Canada. In that case it's not just green because it's hydroelectric, but also because it's inconveniently located hydroelectric it's not displacing more productive uses of the electricity. Maybe geothermal energy in Iceland would be another option.