Battery - theoretical specific energy

  • #1
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Summary:
How to calculate theoretical specific energy
I want to learn how to calculate maximum theoretical specific energy of various battery combinations consisting of a single metal and single oxidant, like for example Sodium - Sulfur, Potassium - Sulfur or even crazy stuff like Rubiddium - Iodine.

I asked this question on stackexchange but I had bad luck as the people there didnt understand what theoretical specific energy is. Its impossible to obtain in real world value based solely on the chemical potential energy between two pure elements, it ignores weight of everything else like electrolyte, separator, electrodes or copper or the metal oxide/carbon where the ions are absorbed inside in real world batteries.

The theoretical specific energy uses watt hour - kilogram units. If you never seen this I highly suggest looking at "metal air battery" Wiki page, there you can see the values for various metal - air ( oxygen ) combinations.

So far I tried calculating it by using molar entalphy of formation energy but I dont know how to do it exactly, especially for combinations that dont have 1 to 1 molar ratio, like for example lithium oxygen where you need twice as many moles of lithium as oxygen.

Here is how I tried doing Lithium - Fluorine, do you see any error?
Lithium molar mass = 6.941g
Fluorine molar mass = 18.99g
Lithium Fluoride molar mass = 25.939g
Lithium Fluoride entalphy of formation = -598.65KJ per mol

1000g : 25.939g = 38.55 LiF moles in 1kg
38.55mol × 598.65KJ/mol = 23077KJ/kg = 6410 Watt hour/kg
 
Last edited:

Answers and Replies

  • #3
mjc123
Science Advisor
Homework Helper
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Strictly, you should use Gibbs energy rather than enthalpy.
 

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