What sodium ion lacks in energy density, it actually partially gains back in the reduced need for cooling. The same properties that make it work across a larger temperature range also mean that you don't need a lot of (or any) cooling/heating to condition the battery. That means less weight is used for that and less energy is needed for running a heat pump.

Another thing here is that volumetric density matters more than weight density in cars. Space comes at a premium and while weight affects efficiency somewhat, it pales in comparison to aerodynamics and rolling resistance. The difference between the best and the worst cars on the road is at least 3x. You have some heavy, brick shaped, monstrosities that barely do 1.5 miles per kwh and then you have some cars with low drag coefficient that easily do 5-6 miles per kwh. Even swapping tires can add meaningful range. Weight reductions help a bit but the difference between the best and worst energy densities on a 60kwh battery is probably 1-2 big passengers in terms of weight.

Peak energy makes sodium ion batteries for energy storage. Their pilot batteries are deployed in a desert. High temperatures during the day, freezing temperatures at night. They use only passive cooling without any moving parts (fans, pumps, etc.). Aside from that being impressive, that also lowers maintenance cost because it reduces the amount of stuff that actually needs servicing.

Sodium ion gains back volume because it doesn't need cooling. At the cell level, they are worse but at the pack level, it starts looking pretty decent. Anyway, there are multiple sodium ion batteries on the road now in China. It's practical right now. The rest is just the widening technology gap the US and EU have with China. We'll just have to wait a few years for local manufacturers to catch up. Some models with these batteries will probably start making it to the EU in the next two years or so.

"Sodium-ion is exciting because..."

Well it is exciting, but not for the reasons you think. More like a Michael Bay movie exciting...there is nothing practical about this design. Most of the cost will be safety systems designed to prevent the battery from being exciting and even then a crash will likely set them off. Pure Na-ion probably isn't viable and certainly isn't viable in a car. Maybe mixing in some Na into the Li-ion to stretch the small amount of Lithium but even then you are significantly increasing the volatility of the battery.

This isn't a practical step, its an act of desperation from people who don't want to admit that large scale electrification is a dumb idea. We electrified everything that made sense to electrify a half century ago.

And the fire safety risks are significantly reduced (thermal runaway is much harder). They can also be transported and stored completely discharged, something not done with lithium ion batteries because of it degrades them much more than regular usage.

The sodium-ion batteries are said to work satisfactorily down to -40 Celsius = -40 Fahrenheit.

-20 Celsius just happens to be a temperature for which a retention ratio was specified in the parent article, and not the limit of the operation range.

> The only part of the battery tech that could affect range is the weight.

Weight is a pretty low factor for cars, sub-percent (aging wheels did a comparison using a pickup empty versus loaded with a pallet of shingles, though with a more efficient vehicle the influence of weight probably shows up more).

Energy density (amount of energy per unit of volume) is a much bigger factor than energy specificity (amount of energy per unit of mass), it means you can either cram more energy in the same volume for more range, or have a lower vehicle with better aero.

> The only part of the battery tech that could affect range is the weight.

Doesn't the charging speed affect how much regenerative braking can be done? If you have to stop fast enough or the battery is sufficiently hot/full/etc. then one that can't charge as fast requires more of the energy to be lost.

Sodium-ion batteries will always be heavier than the best lithium-ion batteries, but for now they have the same energy per kilogram with LFP batteries.

So they have 2 essential advantages over LFP, retention of capacity to much lower temperatures and their cost will become significantly lower when their production technology will be more mature, because they not only do not use lithium, but they also do not use other expensive substances, e.g. nickel or cobalt.

Ok, but the Rivian R1S is a particularly inefficient EV (2-2.5 mi/kWh = 31-25 kWh/100 km). 12.5 kWh/100 km is efficient but not outlandishly so considering these are likely CLTC ranges, which are higher than WLTP which are higher than EPA, and the car in question is not in fact a dumptruck.