Comment by syntaxing
18 hours ago
I’m so desperate for home battery using sodium batteries. Safer and lower temperature it can operate at. Low energy density but I don’t care for home battery.
18 hours ago
I’m so desperate for home battery using sodium batteries. Safer and lower temperature it can operate at. Low energy density but I don’t care for home battery.
I want to have viable replacements for all the old school lithium ion battery packs so that I won't wonder when the day will come that one of the many we have will experience thermal runaway while nobody is around to deal with it. IMO a world where we no longer worry about spontaneous battery fires can't happen soon enough.
Battery voltages are dependent on chemistry, or, standard electrode potentials of metals used. It can't be configured like way past fractions of volts. And Li has about the highest potential among metals, which is kind of the point of using Li. Which means straight swapping NMC cells with any substitute will cause overcharging. Maybe there are cell configurations that could work in series packs, but it can't be simple swap-ins.
You can have an interposer charge controller. It isn't complicated. Many/most cells in consumer products already have one.
LFP batteries are quite a bit safer than the LMN or NMC batteries. The sodium batteries are more stable than LFP I think but I'm not sure how much longer and if that matters too much for home battery usage.
There will probably never be a battery that can power your home but can be used without any kind of worry.
The right thing is to place the battery in a way that you don't have to worry abut the fire, not to expect a high-density battery to be perfectly safe.
Battery safety has very little to do with energy density. High energy density can make the outcomes worse for an unsafe battery, but doesn’t tell you anything about the risk of the fire to begin with.
The reason current Li-ion batteries are unsafe is that they contain a flammable electrolyte. There are batteries with higher energy density that have solid or semi-solid electrolytes. They’re so safe you should probably worry a lot more about driving your car than charging your battery.
Worrying about LFP or So-ion is probably also a waste of time.
LFP batteries are pretty safe. Look up some videos of demonstrations. You can cut them in half with a metal knife and nothing happens besides the loss of capacity, and I suppose the knife heats up from the short-circuit current as well.
I don't know what kind of chemistry shenanigans are going on to make that happen, but it's impressive.
A tank of diesel and a generator are a kind of battery that you have to worry about very little.
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inherently self-limiting processes are nothing rare or special
Standard sodium batteries are much more explosive than LiFE
Can they experience a thermal runaway? Can it be triggered by minor deformations or dents?
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There is an aqueous variant of sodium ion batteries that are safer than lithium, but most sodium ion batteries are NOT that variant and are more dangerous than LiFePO4.
Wait what? All data I see about sodium ion is safer than LFP. I’m by no means an expert and would love to see why it’s the other way around
It's definitely not that cut and dry. Here's a paper with a good breakdown of safety comparisons: https://www.sciencedirect.com/science/article/pii/S2352152X2...
Tldr: while sodium thermal runaways are less dangerous than lithium, they are more likely to happen, and in particular charging a sodium battery to 100% SOC makes thermal runaway significantly more likely than in LFP batteries.
It's true that things like puncture or short circuit are much much less dangerous than with lithium. That is a big part of why the increased thermal runaway risk gets overlooked.
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Sodium batteries will only continue to get cheaper. Cost parity now, but probably closer to 1/2 the price in a few years as production ramps up.
I thought the main advantage in comparison with LFP is the lower price(long term) and better sub-zero performance?
Nope. Almost all batteries I see for LFP have heaters for them at too low temps (around freezing 0C/32F). Where as sodium ion can discharge at -25C
Discharging is not the issue with LiPo4 or other lithium tech. They can work up to negative temperatures without any issue. They can go down to -20°C (-4°F).
The problem is charging the battery at negative, as this damages the internal structure. So you need to heat up the battery (aka, you discharge by warming up heating elements), until you hit the right point. And then you can charge up, what will create heat and thus allow for non-damaging charging.
Some even have a fun trick, where if your going to a EV station with your car (end point route on your build in sat nav). They can start to pre-drain the battery if its really too cold, to warm up the batteries even more. So by the time your at the charger, the batteries are on temperature. I forgot what brand did it that way, seen that feature years ago.
What is different is that Sodium-Ion batteries can charge from negative (i think it was -10°C), as they do not suffer from the same damaging effect.
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There's a yttrium-containing variety of LFP that's supposed to work better at lower temperature (down to -45 C). But yttrium itself is quite expensive ($35/kg).
LFMP variant of LFP with added magnesium mostly solved this. Presently it is not as long-lasting as LFP so is not suitable for home batteries, but it covers typical lifespan of a car and solves the issues with cold climate.
lithium batteries can usually discharge below 0C, it's the charging at sub-zero temperatures that kills them.
Lithium can discharge just fine at -25C without heaters.
Charging it at or around 0C will destroy it extremely rapidly due to electroplating of lithium.
Aren't sodium higher density (at least in terms of energy per weight) than LiFe?
Maybe you're right in terms of energy per volume. Sodium are very light weight in my experience.
No.
The ratio of the stored charge per mass is 23/7 = about 3.3 times higher for lithium than for sodium (7 and 23 are the atomic masses of lithium and sodium), and the voltage can be higher by around 10% for lithium, leading to an even higher energy per mass ratio.
Nonetheless, both sodium and lithium are only a small fraction of the mass of lithium-ion batteries and sodium-ion batteries, so the difference in stored energy per mass is much smaller than for the pure metals.
In practice that means that today LFP batteries and sodium-ion batteries have about the same energy per mass ratio (and similar prices), with both having a lower specific energy than the more expensive NMC lithium-ion batteries.
For now, sodium-ion batteries are very new, so they are still a little more expensive than LFP, but eventually they will be significantly cheaper.
Already now, they have important advantages, so there are applications for which they are preferable even when still more expensive, e.g. where it must be possible to charge them at very low temperatures or where it must be possible to discharge them completely.
No, sodium batteries are less energy dense.
Honestly, yes, re energy density. I hadn’t seen home batteries in-person until a couple of years ago. I was surprised by how small they could actually be (still with a decent capacity). I’d totally trade some of that for chemistry with a less… catastrophic failure mode, and I don’t even have a big house, even for non-US standards.
Not speaking one way or the other on sodium ion’s properties specifically. I see from sibling comments that it’s not straightforward.
yeah, I am waiting to replace my home battery for the safer sodium option whenever it becomes possible. I keep hoping.
Are you in the US?
Yup
I’m hopeful that sodium batteries are going to come down in cost quickly, but if you can find a provider like Base Power or similar where it’s heavily subsidized, there’s a small upfront fee, and they can provide you the economic benefits until sodium batteries reach favorable economic success criteria, that’s a shim until you can replace that with sodium batteries you own outright at a favorable price. You’d have to model what you can get today with a sodium chemistry versus what you can get on offer from one of these battery service providers.
It’s fundamentally a modeling exercise in the forward economic returns curve in the context of your energy needs. Lithium battery lease today as a power purchase agreement (potentially), and then swapping out for a purchased and owned sodium battery pack when the cost hits the right price. It’s always harder to predict the future the further out you attempt to predict, and this technology state of the art is moving very rapidly.