Hello,
I am new to the Materials Project’s molecule module and I am interested in using the computed electron affinity and ionization energies to predict redox potentials.
The Electrolyte Genome Project paper states the following: “The IP and EA are two of most important properties of an electrolyte component [29]. For a salt or solvent, these properties can determine the electrochemical window, which limits the potential within which the battery can operate.”
I am getting hung up on converting these energy values (in eV) to voltages vs. Li/Li+. Is there somewhere in the documentation where this is explained?
Many thanks for your time.
Hi - just bumping this submission. Thanks.
Hi Austin,
Apologies for the slow response!
Since IP and EA are both one-electron processes, you just divide the value in eV by 1 to get to volts. Thus, for these specific properties, the eV and V values are the same. To convert that to voltage vs. Li/Li+, you subtract 1.4, aka the difference between the H/H+ reference electrode and the Li/Li+ electrode. In other words IE-1.4 = oxidation potential (volts vs. Li/Li+) and EA-1.4 = reduction potential (volts vs. Li/Li+).
However, this conversion is already done for you on the molecules explorer. Click on Show / hide columns and select “Oxidation Lithium” and “Reduction Lithium” and the redox potential voltages you’re looking for will be displayed.
I strongly encourage you to use the values displayed once you show the relevant columns because we’re in the process of cleaning up some of our old molecule data which incorrectly has IP / EA and redox potentials set to the same values. Those values are actually the redox potentials, not the IP / EA, thus if you just always use the values displayed by the “Oxidation Lithium” and “Reduction Lithium” then you’ll be safe.
Please let me know if any of this is unclear or if you have any other questions!
Thanks,
Sam
Thanks so much for your explanation, Sam! I did run across a few cases where 1.4V was subtracted and some cases where it was not.
Given the discrepancies in the data, what is the safest way to proceed if I am seeking to query redox potentials vs. Li/Li+ from the REST API rather than from the GUI? Can I query the potentials instead of the IP/EA?
Thanks again for your help.
Hi Austin,
Happy to help 
Have you been able to query molecule data with the REST API? I was under the impression that it could only find materials data, but if you can find molecule entries then yes, you should query the potentials instead of the IP/EA values.
Sincerely,
Sam
Hi Sam!
Yes, you can query molecule information from the API but it doesn’t look like you can query the potentials vs. Li/Li+, as far as I can tell. Would gladly be proven wrong, though.
This issue with unreliable IP/EA data seems like a pretty serious problem affecting the utility of this data set. If I can’t query reliable potentials and/or IP/EA values, is there any way to know which subset of IP/EA data is unreliable so I can avoid it? If not, I would be too afraid to use any of the data at all.
Thanks again!
Hi Austin,
Can you please post the code that you’re using to query molecule information from the API? If you’d prefer, you can also e-mail it to me at [email protected]. I’ll see if I can figure out a way to get the redox potentials directly. I certainly agree that the IP/EA data unreliability is a serious issue and we plan to address it in the near future. But hopefully we can get a solution for you right away so that you don’t have to wait on that larger scale fix.
Sam