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Computational search of anion redox Li-ion battery composition space

963f83cdd6c15fdba1fa247eaf448940?s=47 Dan Davies
February 28, 2021

Computational search of anion redox Li-ion battery composition space

MRS Fall Meeting 2019, EN02.

963f83cdd6c15fdba1fa247eaf448940?s=128

Dan Davies

February 28, 2021
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  1. Computational search of anion redox Li-ion battery composition space Dan

    Davies MRS Fall Meeting EN02 2nd December 2019 @danwdavies
  2. Redox processes in metal oxides M O M redox: Mn

    à Mn+1 Most battery cathodes O redox: O2- à O1- 2p6 à 2p5 Localised “oxygen hole”
  3. Oxygen redox Proc. Roy. Soc. A, 231, 404 (1955)

  4. Oxygen redox Proc. Roy. Soc. A, 231, 404 (1955) S

    = ½ hole on O R. Schnadt, J. Schneider, Phys. Kondens. Materie, 11, 19 (1970)
  5. Anion redox processes M redox: O redox: Mn à Mn+1

    O2- à O1- “Anion redox”
  6. High-throughput materials screening LOW COST HIGH COST Band gap Electron

    energies Likely crystal structure Sustainability … Thermodynamic stability Dynamic stability Electronic structure New energy materials Chemical heuristics Data-driven models Automated calculations (DFT, hybrid DFT and beyond)
  7. Anion redox cathodes 1. Electrostatic environment of O From Madelung

    potentials 2. Orbital overlap From electronic density of states analysis
  8. LiMO2 and Li2 MO3 systems Li O E.g: LiCoO2 LiNiO2

    E.g: Li2 RuO3 Li2 MnO3
  9. Electrostatic environment of O Madelung site potential: In practice calculated

    using Ewald method:
  10. O Madelung potentials Oxygen is very sensitive to its crystal

    environment: High variation in potential within the same crystal structure type 1st row 2nd row 3rd row
  11. Madelung potentials: local O environment In a disordered supercell: Madelung

    site potential decreases when changing the local O coordination environment from TM à Li
  12. Madelung potentials: local O environment In a disordered supercell: Madelung

    site potential decreases when changing the local O coordination environment from TM à Li
  13. Hole localization: the ionic picture Atomic contributions Structural contributions d0

    Strongly favour O holes Increasing d-electrons disfavours M holes (in line with M ionisation energy) J. B. Torrance, R. M. Metzger, Role of the Madelung energy in hole conductivity of copper oxides, Phys. Rev. Lett. 1989
  14. Orbital overlap from DFT calculations E M O U Δ

    Generate possible spin orderings Full relaxation DOS calculation for lowest energy structure 1M. K. Horton et al., High-throughput prediction of the ground-state collinear magnetic order of inorganic materials using Density Functional Theory, npj Comp. Mater. 2019 , , … Magnetic ordering1 Hybrid DFT • HSE06 (25% screened HF exact exchange) • 64 Å3 K-point density • 600 eV energy cut off
  15. Orbital overlap −4 −2 0 2 4 (nergy (eV) ArE.

    unitV TotDO D2S 0g (V) 2 (S) −4 −2 0 2 4 (nergy (eV) ArE. unitV TotDO D2S Cu (d) 2 (S) MgO VBM is ~100% O p-states Cu2 O VBM is ~90% Cu d-states At the two extremes for binary oxides, the VBM can be dominated by O p-states or M d-states
  16. At the two extremes for binary oxides, the VBM can

    be dominated by O p-states or M d-states −4 −2 0 2 4 (nergy (eV) ArE. unitV TotDO D2S 0g (V) 2 (S) −4 −2 0 2 4 (nergy (eV) ArE. unitV TotDO D2S Cu (d) 2 (S) LiCoO2 VBM is ~40% O p-states, ~60% Co d-states −4 −2 0 2 4 (nergy (eV) ArE. unitV TotDO D2S Co (d) 2 (S) Orbital overlap
  17. p-DOS analysis: LiMO2 vs Li2 MO3 LiWO2 Li2 WO3 −2

    −1 0 1 2 (nergy (eV) ArE. uniWV ToWDO D2S W (d) 2 (S) −2 −1 0 1 2 (nergy (eV) ArE. unitV LiRuO2 Li2 RuO3 −2 −1 0 1 2 (nergy (eV) ArE. unitV −2 −1 0 1 2 (nergy (eV) ArE. unitV
  18. p-DOS analysis: LiMO2 vs Li2 MO3 20%-90% range Increase in

    p-character across each TM row (Large JT effect for Fe and reorganisation to square planar for Pt) Fraction of O p-states in upper 1 eV of VBM 1st row 2nd row 3rd row
  19. Summary and ongoing work • Structural and electronic factors influence

    anion redox processes in metal oxides • Qualitative trends can be extracted from electrostatic considerations • The fraction of O p-character can vary from 20% – 90% • The materials design challenge is to tune the fraction deterministically
  20. Acknowledgements • Aron Walsh • David Scanlon (UCL) • Keith

    Butler (Sci-ML, STFC) • Benjamin Morgan (Bath) • Alex Squires (Bath)
  21. Extra: Hole localization: the ionic picture