Sciencemadness Discussion Board - Electrolysis of lithium oxide?

Electrolysis of lithium oxide?

SupFanat - 7-5-2015 at 19:27

Is it possible to get lithium metal and oxygen gas from lithium oxide by electrolysis? Unlike lithium chloride there isn't poisonous chlorine gas as byproduct.

Molecular Manipulations - 7-5-2015 at 19:29

Sure, as long as the 1,438 °C melting point isn't a holdup.

Hawkguy - 7-5-2015 at 19:43

It might be easier just to bite the bullet and go for the LiCl/ KCl mix option. Its not like TONNES of Cl2 are going to be produced anyhow.

SupFanat - 7-5-2015 at 20:16

If the chlorine can be used to produce LiCl from Li₂O then it's fine. If LiClO and LiClO₃ can be broken to LiCl and O₂ then this option must work.

blogfast25 - 8-5-2015 at 01:02

I don't think you have even the foggiest idea what the electrolysis of an LiCl/KCl eutectic entails, but best of luck!

woelen - 8-5-2015 at 10:50

I agree with blogfast25. From the first post in this thread I get the impression that you have no or only little experience with practical chemistry. Doing the kind of things you ask requires access to advanced equipment, which even many well-equipped labs do not have. You talk about it as if you do a 5 minute experiment with material you find in and around the house. The production of toxic chlorine gas is the least of the problems you will encounter when electrolysing LiCl.

Imagine the electrolysis of Li2O or LiCl/KCl mix at several hundreds of degrees Centigrade. If any lithium forms, then it will ignite at once when in contact with air. So, you need protection with an inert gas. The highly reactive lithium requires a noble gas as protection.

Furthermore, you need electrodes capable of withstanding the extremely demanding environment in which they have to operate (strongly oxidizing at anode, strongly reducing at cathode, and very high temperature in a molten salt). Only few materials withstand such conditions.

gdflp - 8-5-2015 at 11:07

Quote: Originally posted by woelen

Imagine the electrolysis of Li2O or LiCl/KCl mix at several hundreds of degrees Centigrade. If any lithium forms, then it will ignite at once when in contact with air. So, you need protection with an inert gas.

Interestingly enough, you don't actually need an inert gas cover during the electrolysis. As len1 described in his book, the molten electrolyte forms a thin film over the molten lithium which protects it from the atmosphere. Once the lithium is collected from the cell however, this surface layer is broken and thus the lithium must be transferred to paraffin oil as quickly as possible.

blogfast25 - 8-5-2015 at 11:44

Quote: Originally posted by gdflp

Density of Li at MP = 0.512.

DANG!!!

Specific cathode design can of course contain the metal under electrode/electrolyte. Without such a design it will float on just about ANYTHING!

I think you may referring to len1's sodium cell. NOT the same!

[Edited on 8-5-2015 by blogfast25]

WGTR - 8-5-2015 at 12:15

I remember reading something similar in len's book. He said something to the effect that the molten salt forms a transparent skin over the molten lithium metal, protecting it from ignition unless it is disturbed.

Unfortunately, I can't access the relevant pages anymore. I suppose I could just buy the book, right?

blogfast25 - 8-5-2015 at 12:47

Quote: Originally posted by WGTR

I remember reading something similar in len's book. He said something to the effect that the molten salt forms a transparent skin over the molten lithium metal, protecting it from ignition unless it is disturbed.

Well, if you trust a thin skin of salt over a super reactive metal at 500 C or so, go right ahead!

gdflp - 8-5-2015 at 13:20

Quote: Originally posted by blogfast25

Quote: Originally posted by gdflp

Nope, I'm not. The following is a quote from len1's book, it's a caption under a photograph.

Quote:

A lithium globule on the surface
of a molten KCl–LiCl eutectic at 420°C after electrolysis. At this temperature, lithium
ordinarily burns in air; however, a thin film of electrolyte protects it. The film is made visible
by traces of carbon from the anode adhering to the surface.

blogfast25 - 8-5-2015 at 13:22

gdflp:

Fair enough.

Litmus test: would you trust that to make small amounts of Li? Looks more like an interesting gimmick to me than a viable and safe preparation of Li metal.

[Edited on 8-5-2015 by blogfast25]

WGTR - 8-5-2015 at 14:31

Personally, I prefer to avoid molten lithium whenever possible, protective salt layer or not. For very small amounts I electrolyze a molten nitrate bath (instead of the chloride melt). This has a lower melting point than the halide melts, and allows the lithium to be produced as a solid. Lithium reacts with the nitrate anion, but the produced lithia is stable and non-soluble in the melt. It is also a fast ion conductor for lithium ions. I posted some results earlier here:

https://www.sciencemadness.org/whisper/viewthread.php?tid=19...

Something that would be useful would be to try modifying the plating parameters. Perhaps pulse or pulse-reverse plating would keep the deposit from becoming dendritic.

DraconicAcid - 8-5-2015 at 14:37

Molten lithium salts can make a mess out of glass, too.

blogfast25 - 8-5-2015 at 16:12

Kudos to gdflp for providing me a free *.pdf of len1's book, which I've long wanted to peruse.

His electrolysis of LiCl/KCl in a graphite crucible requires no inert gas due to formation of a protective LiCl layer on the liquid Li meta. Quite amazing. But I'd still feel more comfortable with an argon blanket.

blogfast25 - 8-5-2015 at 16:34

No worries, 'Dude'. 'Cool'.

420MLGnOhEADsCOPEpro - 9-5-2015 at 16:53

supposing that you can achieve the required temperature the design of the apparatus will be a challenge at the least
as far as i am aware the best electrodes are -iron and +carbon as the iron will not react with the lithium and the carbon will react with the oxygen but in the process will leave as CO and CO2 (lithium carbonate won't form as it decomposes at ~1310C)
but what isn't easy is the insulation as it must be
an insulator (duh) thus solid and ionicly or covalently bonded
temperature resistant to ~1440C
non soluble in Li2O
i am aware of no suitable materials as ionic oxides like CaO should dissolve with ease and covalent oxides like Al2O3 react to form oxyanions
i only know that Al2O3 and SiO2 react as such though so there may be exceptions
i think FeO may be an exception though i've found no sources

SupFanat - 15-5-2015 at 15:30

This thread is a part of overall idea that renewable energy can be stored by using it for electrolysis.

Reaction of LiOH with Cl₂, decomposition of LiClO or LiClO₃ so that only LiCl remains and electrolysis of LiCl would give the same result.

I understand that such experiments shouldn't be done at home. I never said that I'm going to do it at home.

420MLGnOhEADsCOPEpro - 15-5-2015 at 21:06

Quote: Originally posted by SupFanat

This thread is a part of overall idea that renewable energy can be stored by using it for electrolysis.

Reaction of LiOH with Cl₂, decomposition of LiClO or LiClO₃ so that only LiCl remains and electrolysis of LiCl would give the same result.

in that case why not just bottle the chlorine produced by electrolysis
chlorine liquefies at 0.74 MPa and thus can be stored in as a liquid in a tank rated to 1.5 MPa
liquid chlorine has a density of ~1.5 g/c^3
assuming a spherical tank made of 1 mm thick steel with a tensile strength of 1 GPa i get a radius of 1.3333 m, a volume of 9.93 m^3, and thus a mass of 14.9 tonnes, and assuming 90% efficient energy collecting when burned back to LiCl 42,958 KWH which is ~$4,000 in electricity

it can then later be burned with the lithium to release more energy than oxygen would
if pressurized chlorine is a concern either a cryogenic tank or bromine could be used instead
both options see a small loss in efficiency