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#1 2018-01-12 14:36:41

Terraformer
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From: Lancashire
Registered: 2007-08-27
Posts: 2,541
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Sodium-Iron battery?

I've been thinking about potential battery chemistries that use the most abundant elements on Earth, since nickel, lead, and lithium are not abundant enough for us to replace all our power usage as a species with intermittent renewables. Sodium-ion is promising, and I've been thinking about potential replacements for nickel in nickel-iron batteries, which led to the idea for a sodium-ion battery that would use sodium hydroxide as an electrolyte. In particular, a simple design made from easily accessed materials that could be added to the open source ecology global village construction set.

I put the idea up on Halfbakery, and so far no-one has given an explanation of why it wouldn't work. I can't see a reason it wouldn't myself (hence why I'm sharing it), but perhaps someone here is more knowledgeable about electro-chemistry than I am.

I wrote:

The battery comprises an iron plate serving as an anode, a (probably tin coated) graphite [okay, should be cellulose] cathode, and sodium hydroxide as an electrolyte. During charging, sodium ions would migrate to the cathode and become intercalated into it, whilst hydroxyl ions would react with the iron to form iron hydroxide. When the battery is discharging, this would occur in reverse.

The advantage this battery has is that the materials needed to produce it are all incredibly cheap. The disadvantage is that it may not work. I really have no idea. Low capacity isn't an issue if the cost is low enough, since they would only be used for stationary applications anyway.


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#2 2018-01-12 16:29:30

Midoshi
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From: Colorado
Registered: 2007-07-14
Posts: 155

Re: Sodium-Iron battery?

Terraformer, maybe I am mistaken, but what you describe sounds similar to a nickel-iron battery, though they use a nickel cathode instead of carbon (obviously), and usually employ a potassium hydroxide solution (though it appears sodium hydroxide can also be used).

https://en.wikipedia.org/wiki/Nickel%E2 … on_battery

It seems some researchers have recently worked on updating this old technology by adding carbon to the mix:

https://news.stanford.edu/news/2012/jun … 62612.html

So it seems that you have hit upon a good idea, and the details are in the engineering.


"Everything should be made as simple as possible, but no simpler." - Albert Einstein

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#3 2018-01-13 04:27:53

Terraformer
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From: Lancashire
Registered: 2007-08-27
Posts: 2,541
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Re: Sodium-Iron battery?

It's similar to an NiFe battery at the iron end, with the same redox reaction. At the other end, it would remove sodium ions from the solution to provide the hydroxyl ions for the reaction, rather than have nickel ion give them up.


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#4 2018-01-13 12:30:48

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 10,843

Re: Sodium-Iron battery?

https://en.wikipedia.org/wiki/Nickel%E2 … on_battery

The nickel-iron battery (NiFe battery) or "edison cell" is a storage battery having a nickel oxide-hydroxide cathode and an iron anode, with an electrolyte of potassium hydroxide (lye can be used as a substitute). The nickel–iron battery (NiFe battery) is a rechargeable battery having nickel(III) oxide-hydroxide positive plates and iron negative plates, with an electrolyte of potassium hydroxide. The active materials are held in nickel-plated steel tubes or perforated pockets. The Nickel-Iron batteries, are idea for solar power and renewable energy products, Iron Edison is providing people with off-grid, clean energy solutions.

http://ironedison.com/

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#5 2018-01-17 13:59:33

JoshNH4H
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From: New York, NY, USA, Earth, Sol
Registered: 2007-07-15
Posts: 2,208
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Re: Sodium-Iron battery?

NiFe and NaFe batteries have the advantage of being quite similar.  They only differ by one letter!

I like the idea but I don't know enough about battery tech to confidently say if it will work or not.


-Josh

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#6 Yesterday 05:08:22

Terraformer
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From: Lancashire
Registered: 2007-08-27
Posts: 2,541
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Re: Sodium-Iron battery?

Tin coated cellulose has been used as an anode in sodium-ion batteries - Kurzweilai. Since lye soaked cellulose should conduct electricity (it works with salt water, at least), I wonder if we could dispense with the tin coating, allowing us to build a battery out of iron, paper, and lye?

I really ought to dig out my chemistry kit in that case. It shouldn't be difficult to test.


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#7 Yesterday 16:44:56

JoshNH4H
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Re: Sodium-Iron battery?

I think it's problematic to build a sodium battery that uses water for any part of it as metallic sodium and water tend to react rather violently.

I suspect you'll end up with something more like an electrolysis cell, where reduction of the Iron anode reduces the required voltage for electrolysis somewhat.

In that case NaCl might actually be an even better electrolyte as FeCl2 and FeCl3 are soluble in water while Fe(OH)2 and Fe(OH)3 are less so.  But I digress.

This would work as a molten salt battery, presumably, but that's a bit harder than Iron, paper, and lye.  It looks like Lithium Ion Batteries use LiXFy compounds (For example LiPF4) in various organics (Wikipedia suggests ethylene carbonate, dimethyl carbonate, and diethyl carbonate).

Also, I learned today that in a lithium ion battery Lithium is being reduced, and Cobalt is being oxidized from the +4 to +3 state.  Interesting stuff!

It looks like you might be able to get away with Methanol, actually.  NaCl is somewhat soluble and FeCl3 is very soluble.  Wiki doesn't say anything about FeCl2, though, so you may want to check.  I don't remember offhand how to check that it won't produce chlorine gas, but you'll definitely want to look into that as well.

I take it back--Sodium reacts violently with alcohols.  My bad!

The trick I suppose is finding a solvent that won't react with Sodium but will dissolve a compound of Sodium and Iron.  Formamide might do the trick but information is hard to find and that's not a nice chemical to deal with because it has the unfortunate habit of sometimes decomposing to HCN gas.


-Josh

If you try to talk to me about cold fusion or propellantless drives I will ignore you.
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#8 Today 06:44:29

Terraformer
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From: Lancashire
Registered: 2007-08-27
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Re: Sodium-Iron battery?

I'm not sure the batteries operation would actually involve metallic sodium. It depends on how the sodium is trapped in the anode. Is it kept in metallic form, or as positive ions in a negatively charged structure? If the latter, there shouldn't be a problem.

The impression I get from the KurzweilAI article is that the cellulose anodes store them as ions, so it should be okay.

Last edited by Terraformer (Today 06:45:47)


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#9 Today 07:07:24

JoshNH4H
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Re: Sodium-Iron battery?

The thing is that batteries work based on a Redox reaction.  So before charging you have Na+ and Fe0.  Then you charge it by taking electrons from Fe and giving them to Na to make it neutral.  When you're discharging you do the opposite.  When the battery is 100% discharged there's no metallic sodium but by necessity there is when it's got energy to give up.

The battery reaction (assuming we use chlorides) is as follows:

Fe+3 NaCl+energy <-> FeCl3 + 3 Na

The flow of electrons from Fe to Na is the current flowing through the wires attached to the battery.


-Josh

If you try to talk to me about cold fusion or propellantless drives I will ignore you.
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#10 Today 08:26:55

Terraformer
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From: Lancashire
Registered: 2007-08-27
Posts: 2,541
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Re: Sodium-Iron battery?

Again, that doesn't seem to be how it works in the cellulose anode. It seems to be instead storing electrons as a negatively charged structure, with the charge balanced by the inclusion of sodium ions.

As I understand it, in lithium-ion batteries, the lithium starts in a neutral state when it's discharged. and is stored as lithium ions when the battery is charged. But either way, it gets stored as ions at some point.

How I'm thinking the battery would work is, electrons are put into the cellulose anode, which exchanges hydroxyl ions for sodium ions to balance the charge, resulting in a negatively charge cellulose mesh incorporating positive sodium ions to keep the charge neutral. The hydroxyl ions are then stored by reacting with the iron cathode to form iron hydroxide, releasing electrons which completes the circuit. This is reversed when the battery is discharged.


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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