LMO (LiMn2O4) electrode entry

Materials Project
1

Hi!
I am looking for a battery entry for the well-known, spinel-like LiMn2O4 (LMO), but am facing some problems.
I found a material entry (mp-25015) that seems to correspond to the above mentioned phase (it’s observed, right symmetry etc), but cannot find any electrode entry having this material as lithiated state. I’d conclude from this that MP hasn’t carried out an electrode calculation involving this material yet, but the webpage I open the mp-25015 entry on displays a different ID in the bookmark on top, that is mp-22584.
Now, an electrode entry named mp-22584_Li exists, and seems to contain another spinel-like LiMn2O4, just different from the one I’m looking for.

Do you think there might be an error, and that the well-known mp-25015 should indeed appear within the mp-22584_Li electrode entry? Or is the mp-25015 lithiation not done yet?

Thank you!

2

Hi @acarnevali, so it looks like mp-25015 is a task_id (id given to a specific calculation) that is associated with mp-22584 which is the official designated mp-id for that structure. So mp-25015 is not a valid material id since it was structurally matched to mp-22584 but has a higher numerical value (the material id is determined by the task id with the lowest value)

You can see this from the new API:

from pymatgen.ext.matproj import MPRester
mpr = MPRester(<NEWAPIKEY>)
matdoc, = mpr.materials.search(task_ids=["mp-25015"])
print(matdoc.material_id)
print(matdoc.task_ids)

mp-22584
[MPID(mp-601385), MPID(mp-905589), MPID(mp-1104912), 
MPID(mp-1103719), MPID(mp-1440945), MPID(mp-1786538), 
MPID(mp-919667), MPID(mp-1103495), MPID(*mp-22584*), 
MPID(mp-918667), MPID(mp-1922093), MPID(*mp-25015*), 
MPID(mp-1687590), MPID(mp-1103468), MPID(mp-1104391)]
3

Hi @jshen! Thank you, it’s very clear now. Indeed I can only find mp-25015 on the old website.
Was wondering though: given that mp-22584 exists as a material entry, why does it not appear among the phases of the mp-22584_Li electrode?

4

So the electrode is defined on a 1-D topotactic subspace of the phase diagram and the voltages steps correspond to the facets of this 1-D subspace (lines between two stable phases).
I’m going to guess that mp-22584 is just higher in energy compared to the linear interpolations between the two most stable states at adjacent lithiation levels.

This is all kind of under-the-hood detail that causes so much confusion I really need to write this up …

5

I see, it makes sense. In this specific case, the “real” spinel LMO (mp-22584) seems to be outclassed in stability by a theoretical phase ( mp-1272804) that is spinel-like and 0 eV above the hull. One could argue that it’s kind of wrong to consider the spinel LMO mp-22584 as the “right”, legitimate LiMn2O4 phase of the electrode: mp-22584_Li simply describes a theoretical electrode that thermodynamically passes for mp-1272804 as its LiMn2O4 phase.

Anyway, it’s a pity that real-world, known electrode materials like LMO in this case, but also NCM materials seem not to have dedicated electrode entries. Hope the blanks will be filled in soon (unless it’s just me who might have not found them)!

Thank you for your help!