Abstract
Constrained density functional theory at the GGA+U level, within
the Blue Moon ensemble, as implemented in the VASP code, is applied to
simulate aqueous dissolution of lithium manganate spinel, a candidate
cathode material for lithium ion batteries. Ions are dissolved from
stoichiometric slabs of composition LiMn2O4, with
orientations (001) and (110), embedded in a cell with 20 Å water
channels between periodically repeated slabs. Analysis of the Blue Moon
ensemble forces for dissolution of Li, Mn, and O ions from lithium
manganate indicate that bond breaking occurs sequentially, ordered from
weak to strong bonds, where bond breaking occurs when a bond length is
stretched about 50% relative to its equilibrium value. Substrate ions
are displaced to maintain bond lengths close to equilibrium for bonds
other than that the one being broken. The predicted free energies
required to break the chemical bonds with the LiMn2O4 substrate are Mn3+, 1.4; O2–, 1.0; Mn2+, 0.8; and Li+, 0.35, in eV; an existing experimental measurement (Lu, C. H.; Lin, S. W. J. Mater. Res.2002, 17,
1476) had yielded an effective dissolution activation energy of 0.7 eV.
A mechanism for the role of acid in promoting lithium manganate
dissolution is discussed.
Original language | English |
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Pages (from-to) | 4050-4059 |
Number of pages | 10 |
Journal | The Journal of Physical Chemistry Part C (Nanomaterials and Interfaces) |
Volume | 116 |
Issue number | 6 |
DOIs | |
Publication status | Published - 2012 |
Austrian Fields of Science 2012
- 103018 Materials physics