China is already selling two EVs using sodium ion batteries.
Sodium ion batteries won’t be a general drop-in substitute in vehicles for lithium.
It might be possible to use sodium-ion batteries in place of some not-energy-density critical lithium-ion applications (the way lead-acid is currently used for some lithium-ion applications), and that’d free up some materials for EV use.
However, sodium and lithium atoms have differences, two of which are relevant for battery performance. The first difference is in the so-called redox potential, which characterizes the tendency for an atom or molecule to gain or lose electrons in a chemical reaction. The redox potential of sodium is 2.71 V, about 10% lower than that of lithium, which means sodium-ion batteries supply less energy—for each ion that arrives in the cathode—than lithium-ion batteries. The second difference is that the mass of sodium is 3 times that of lithium.
Together these differences result in an energy density for sodium-ion batteries that is at least 30% lower than that of lithium-ion batteries [1]. When considering electric vehicle applications, this lower energy density means that a person can’t drive as far with a sodium-ion battery as with a similarly sized lithium-ion battery. In terms of this driving range, “sodium can’t beat lithium,” Tarascon says.
In time, sodium-ion batteries will improve, but their driving range will never surpass the top-of-the-line lithium-ion batteries, Tarascon says. He imagines instead that sodium-ion technology will fill specific niches, such as batteries for smaller, single-person electric vehicles or for vehicles that have a range of only 30–50 miles (50–80 km). Weil agrees, but he says that society may have to change the way it views automobiles. “We cannot only point to the technology developers and say, ‘We need more efficiency.’ It’s even more important to stress that we need more ‘sufficiency,’ which is people being satisfied with a small car,” he says.