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Comment by samatman | Hacker News Reader

I'd bet a decent amount of money that most electric cars in the developed world will still use the Goodenough chemistry in ten years.

The theoretical energy density of sodium is too low for the weight, this isn't a matter of developing the technology.

What we can look forward to is sodium batteries becoming cheap and reliable, replacing every application of lead-acid, and most, perhaps all, stationary lithium. Great choice for house or grid-level storage, where the lower density is basically harmless.

Batteries are such a major component of an electric car that there's a sort of Rocket Equation which applies: a sodium car with the same range as a lithium one would have to carry so much more battery that one would have to add substantially more just to move the extra weight around.

This will never pencil out.

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That all makes sense about the weight, and it will likely matter for airplanes. But it doesn't matter enough for cars.

LFP (lithium iron phosphate) batteries are already used by Tesla and have a gravimetric energy density of 125 Wh/kg, much lower than Lithium-ion.

CATL currently produces a sodium-ion battery at 160 Wh/kg, and they expect the next generation to reach 200 Wh/kg. Even if that doesn't come to fruition, it's already higher density than what's being used in electric cars!

Now consider that sodium-ion is less flammable and doesn't have the risk of thermal runaway. You might be able to drop weight in hazard protection systems. Battery cycle times are competitive with Lithium chemistry. Contrary to your prediction that it doesn't pencil out, I expect sodium-ion to completely displace Lithium batteries for use in electric vehicles because it pencils out so much better. It will just be so much cheaper and doesn't bottleneck on any materials as you scale up.

As someone who occasionally walks and often cycles, I really hope batteries that are even heavier than lithium don't become commonplace.

Why? compare the weight of SUVs or trucks. It's more than the battery weight, so better hope for smaller vehicles.

I hope for smaller vehicles as well. It's hard to separate "big" and "heavy" statistically because they are highly correlated, but in general, heavier vehicles means higher likelihood of fatality in a crash 1. I suppose we will be doing a natural experiment to tease out the difference over the years as heavy EVs become more commonplace and pedestrian fatalities continue to increase.

> It’s also about weight. Trucks today averaging around 5200 pounds -- that’s a jump of more than a half ton since 2000. And things get heavier as electric vehicles look to become our new normal.

> On average electric vehicles are 10 percent heavier than gas powered cars. For instance, the new electric Hummer weighs in at a staggering 9,100 pounds or more than 4 and a half tons. All that weight can have deadly consequences. Researchers have found that for every 1,000 pounds a car puts on, a pedestrian is nearly 50 percent more likely to die if they’re hit and the more a truck weighs the longer it will take to stop.

1. https://www.clickondetroit.com/news/2022/08/08/size-does-mat...

I dunno that "lighter cars" is a realistic thing to hope for at this point. I do hope to see better bumper crush zone designs, more protected bike lanes, blinking crosswalks, better in-vehicle collision detection systems, etc.

Even if a "lighter" car hits you, it's gonna be a bad day. Better to avoid the collision altogether, no? :)

I "hope" for lighter cars in the same way I "hope" we start taking necessary drastic measures to combat climate change, which is by knowing that it won't happen and advocating for change anyway.

On the other hand, I think maybe hoping that vehicles become no heavier than modern EVs is at least somewhat realistic.

>LFP (lithium iron phosphate) batteries are already used by Tesla and have a gravimetric energy density of 125 Wh/kg, much lower than Lithium-ion.

Tesla uses iron phosphate in its cheaper models, but the high end is still reliant on NMC. I'd be interested to know the maximum range available on LFP.

BYD sells a lithium-iron-phosphate battery with an energy density of 150 Wh/kg. CATL's LFP is 125.

Also, a lithium-iron-phosphate battery is a lithium-ion battery, in that the electrolyte works by lithium ionic conduction. The appropriate contrast would be "lithium-nickel".

>CATL currently produces a sodium-ion battery at 160 Wh/kg, and they expect the next generation to reach 200 Wh/kg.

This is reported as the "single-cell" energy density, and is not directly comparable to the battery pack density.

>Now consider that sodium-ion is less flammable and doesn't have the risk of thermal runaway.

Surely this isn't because of the stability of sodium, which anyone who watched that chemistry demonstration in high school knows, is significantly more reactive than lithium. I expect the risks to be similar; furthermore, the concept of a dense energy storage that has no risk of sudden release is physically unlikely.

> Tesla uses iron phosphate in its cheaper models, but the high end is still reliant on NMC. I'd be interested to know the maximum range available on LFP.

In theory 490 km, in practice, 380 km. Because they don't degrade as much, after a few years they are closer to what you call the high end models.

> Also, a lithium-iron-phosphate battery is a lithium-ion battery, in that the electrolyte works by lithium ionic conduction. The appropriate contrast would be "lithium-nickel".

Correct, I want to point out that John Goodenough was responsible for the basic research which lead to all lithium-ion batteries.

I explicitly intended LiFePO to be included, and I hope for a variety of reasons that it's much more popular than cobalt-heavy formulas in ten years.

Only now do I realise that "Goodenough" is a real person's name, and neither a placeholder name nor a case of Emphasis Via Capital Letters:

https://en.wikipedia.org/wiki/John_B._Goodenough

I have been interested in the technology from TexPower:

https://texpowerev.com/

They offer a lithium-nickel chemistry without cobalt. If it can be proven in practice, it would allow comparable density to the best car batteries in a scalable chemistry. The founder is a researcher at the University of Texas who wrote several papers on the chemistry:

https://onlinelibrary.wiley.com/doi/pdf/10.1002/adma.2020027...

https://www.sciencedirect.com/science/article/pii/S240582972...

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/aenm.2...

> Batteries are such a major component of an electric car that there's a sort of Rocket Equation which applies: a sodium car with the same range as a lithium one would have to carry so much more battery that one would have to add substantially more just to move the extra weight around.

This is absolutely not clear. Active lithium is just ~60g per kWh in a battery, or ~1% of the mass of a state of the art LFP battery. Even though sodium weighs 3.5 times more for the same charge, if it's use would allow just a few percent reduction in total weigh, either by reduction of inactive cathode material or some other source, it could easily beat lithium batteries.

Type of material decides on battery's energy density. It's just impossible for battery of "inferior" chemistry to get to same level of capacity.

There is a reason lead ones are not "just" heavy but also physically much bigger than same capacity lithium one.

What will (probably) happen if we get competitive sodium batteries is that they will phase out lithium from the stationary storage so there won't be that huge demand for lithium for everything. Or possibly they will become "cheap EV's battery"

Stationary storage will more like be taken over by iron batteries which are much cheaper. Sodium batteries will happen in cars because not everyone needs really long range.

Sodium is both heavier and less energetic, enough so that the equation points to a worse car: heavier than a car which goes substantially further.

Sodium cannot improve lithium by replacing it in batteries, for physical chemistry reasons which can't be negotiated.

I don't consider it likely that lithium will become so much more expensive that people will want their second-largest purchase, a car, to be inferior in the way that it must be with sodium batteries.

Rather more likely that cheap and good sodium batteries relieve pressure on lithium supply for the enormous amount of battery storage we need to handle intermittent renewables.

If a significant proportion of a lithium battery was lithium, this would absolutely be true.

By weight, something around 1% of a lithium battery is lithium.

Sodium is seen as an interesting alternative, because there are some indications that it can make that 99% that makes up the rest of the battery lighter. Even though sodium is ~3.5 times worse as a charge carrier, if it's use allows cutting enough weight from that rest, it can be a winner overall.

For example, aluminium is, for complex reasons, not compatible with every part of a li-ion battery, and so they use copper connectors internally, typically containing by weight at least 10 times as much copper as they contain lithium. Sodium batteries can use aluminum everywhere, which saves on not just cost, but also more in weight than the weight difference between equal molar amounts of sodium and lithium.

150Wh/kg is completely fine. A small vehicle with a 100kg battery can do 95% of what is needed for the average person (or as a second family car), it's just a matter of whether the trend of legislating sane vehicles out of existence continues.

Sulfur has entered the room.

I did say ten years, rather than more.

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