Battery - theoretical specific energy

AI Thread Summary
The discussion focuses on calculating the maximum theoretical specific energy of various battery combinations using single metals and oxidants, such as Sodium-Sulfur and Lithium-Fluorine. The theoretical specific energy, measured in watt hours per kilogram, is derived from the chemical potential energy of pure elements but does not account for practical factors like electrolytes and electrodes. The user seeks clarification on their calculation method, particularly for combinations with non-1:1 molar ratios, and shares their approach using Lithium-Fluorine as an example. They express uncertainty about the accuracy of their calculations and mention that using Gibbs energy is more appropriate than enthalpy for these calculations. The conversation emphasizes the importance of understanding theoretical versus practical energy values in battery chemistry.
Solitron
Messages
1
Reaction score
1
TL;DR 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 don't know how to do it exactly, especially for combinations that don't 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:
Engineering news on Phys.org
Strictly, you should use Gibbs energy rather than enthalpy.
 
Hello! I've been brainstorming on how to prevent a lot of ferrofluid droplets that are in the same container. This is for an art idea that I have (I absolutely love it when science and art come together) where I want it to look like a murmuration of starlings. Here's a link of what they look like: How could I make this happen? The only way I can think of to achieve the desired effect is to have varying droplet sizes of ferrofluid suspended in a clear viscous liquid. Im hoping for the...
Hello everyone! I am curious to learn how laboratories handle in-house chip manufacturing using soft lithography for microfluidics research. In the lab where I worked, only the mask for lithography was made by an external company, whereas the mold and chip fabrication were carried out by us. The process of making PDMS chips required around 30 min–1 h of manual work between prepolymer casting, punching/cutting, and plasma bonding. However, the total time required to make them was around 4...
Back
Top