High energy Aluminum-Sodium battery

[Moreno]

I've met such statements that energy which a battery can deliver roughly depends on Fermi energy differences between anode and cathode materials. If we look in the table with Fermi energy values for pure metals, there exist large difference between Aluminum (12 eV) and Sodium (3 eV). http://hyperphysics.phy-astr.gsu.edu/hbase/Tables/fermi.html#c1 Both materials are inexpensive. Can we create an Aluminum-Sodium battery and if yes, how much energy will it offer?

Edited August 20, 2017 by Moreno

[John Cuthber]

3 hours ago, Moreno said:

've met such statements that energy which a battery can deliver roughly depends on Fermi energy differences between anode and cathode materials.

Where, and did they say why?

[Moreno]

4 minutes ago, John Cuthber said:

Where, and did they say why?

Quote

Confusingly, the term "Fermi energy" is often being used for referring to a different yet closely related concept, the Fermi level (also called electrochemical potential).

Quote

In electrochemistry, the electrochemical potential, μ, sometimes abbreviated to ECP, is a thermodynamic measure of chemical potential that does not omit the energy contribution of electrostatics. Electrochemical potential is expressed in the unit of J/mol.

Quote

Electrochemical potential is important in biological processes that involve molecular diffusion across membranes, in electroanalytical chemistry, and industrial applications such as batteries and fuel cells. It represents one of the many interchangeable forms of potential energy through which energy may be conserved.

https://en.wikipedia.org/wiki/Electrochemical_potential

Quote

If the emphasis is on the underlying electrochemistry, the cell notation is stripped of ... caused by the different positions of the Fermi energies in the two metals.

 

[John Cuthber]

Does any of those say "energy which a battery can deliver roughly depends on Fermi energy differences"?

I am certain that no electrochemical cell will produce anything like 12 volts.

 

[Moreno]

1 hour ago, John Cuthber said:

Does any of those say "energy which a battery can deliver roughly depends on Fermi energy differences"?

I am certain that no electrochemical cell will produce anything like 12 volts.

 

This is what some person (who seem to be profi in batteries) claimed.

And for example:

Quote

During discharge, a cell plates the metal of an anode of high-energy Fermi level such as lithium or sodium onto a cathode current collector with a low-energy Fermi level; the voltage of the cell may be determined by a cathode redox center having an energy between the Fermi levels of the anode and that of the cathode current collector.

https://docs.wind-watch.org/braga2017.pdf

If I no make mistake Fermi energy depends primarily (if not completely) on electron concentration inside of metal.

Therefore electrons are prone to flow from high Fermi energy (higher concentration) to low Fermi level.

Edited August 20, 2017 by Moreno

[Sensei]

High energy (...) battery

For what purpose?

If you want to have 12 V, connect 8 1.5 V batteries in serial.

If you want to have 9 V, connect 6 1.5 V batteries in serial.

If you want to have 4.5 V, connect 3 1.5 V batteries in serial.

If you want to have 3 V, connect 2 1.5 V batteries in serial.

 

[Moreno]

1 hour ago, Sensei said:

 

 

For what purpose?

If you want to have 12 V, connect 8 1.5 V batteries in serial.

If you want to have 9 V, connect 6 1.5 V batteries in serial.

If you want to have 4.5 V, connect 3 1.5 V batteries in serial.

If you want to have 3 V, connect 2 1.5 V batteries in serial.

 

For example, for automotive applications. Energy is measured not in volts, but in MJ/Kg or W-h/Kg. It is not only voltage is important, but also electrochemical equivalent (how many electrons you can obtain per atom). Aluminum can offer 3 electrons per atom, what is good.

[Sensei]

On 8/21/2017 at 2:29 AM, Moreno said:

For example, for automotive applications. Energy is measured not in volts, but in MJ/Kg or W-h/Kg.

It's energy density/specific energy, rather than energy.

Energy density/specific energy is measured in J/m^3 (E/V) or J/kg (E/m).

https://en.wikipedia.org/wiki/Energy_density

https://en.wikipedia.org/wiki/Specific_energy

On 8/21/2017 at 2:29 AM, Moreno said:

It is not only voltage is important,

Yes, it's important. If you will try to use 12 V battery to lighten up LED diode (which needs <3.5 V) you will lose a lot of energy (or there will be needed voltage dividers etc.)...

On 8/21/2017 at 2:29 AM, Moreno said:

but also electrochemical equivalent (how many electrons you can obtain per atom). Aluminum can offer 3 electrons per atom, what is good.

You're not taking into account two things:

- density of medium (Al = 2.7 g/cm^3)

- whether battery will be possible to be made rechargeable.

Battery which is impossible to be recharged, is useless for automobile industry..

 

[Moreno]

To Sensei:

Why do you think I don't take into account density of Aluminum and why high density is bad?

I expected it should be rather good. High density + 3 free electrons per atom = high Fermi energy.

I don't know if it can be rechargeable, I want hope yes.

I want to know if it's possible to create a battery which would exploit difference in Fermi energies between metal crystal structures rather than chemical properties of individual atoms.

Aluminum and Sodium don't regularly suppose to react anyhow, but possibly their Fermi energies can come to equilibrium even if we will obtain mechanical atomic mixture of both elements? Will Aluminum form a uniform atomic mixture with Sodium or will rather form a macroscopic crystals inside of it? If it will work than there should be even lesser problem to make such battery rechargeable since there will be no strong chemical bonds between the heterogeneous atoms.