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Intrinsic differences between LiMnPO4 and LiFePO4

Intrinsic differences between LiMnPO4 and LiFePO4. Insights from First Principles Calculations. Shyue Ping Ong, Vincent L. Chevrier , Anubhav Jain, Geoffroy Hautier , Gerbrand Ceder. Outline. LiMnPO 4 vs LiFePO 4 : Experimental observations Polaron migration barriers

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Intrinsic differences between LiMnPO4 and LiFePO4

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  1. Intrinsic differences between LiMnPO4 and LiFePO4 Insights from First Principles Calculations Shyue Ping Ong, Vincent L. Chevrier, Anubhav Jain, GeoffroyHautier, GerbrandCeder Shyue Ping Ong, Vincent L. Chevrier, Anubhav Jain, Geoffroy Hautier, Gerbrand Ceder

  2. Outline • LiMnPO4vs LiFePO4 : Experimental observations • Polaron migration barriers • Are the polaron migration barriers in LiMnPO4 significantly different from LiFePO4? • Implications for electronic conductivity • Thermal stability of charged cathode • At what temperature does delithiated LiMPO4 begin to evolve oxygen? • Conclusions Shyue Ping Ong, Vincent L. Chevrier, Anubhav Jain, Geoffroy Hautier, Gerbrand Ceder

  3. LiMnPO4 vs LiFePO4 LiMnPO4 LiFePO4 3.5V 170 mAh/g σ~10-8 S/cm Charged state evolves O2 at ~500ΟC M. Yonemura, A. Yamada, Y. Takei, N. Sonoyama, and R. Kanno, J. Electrochem. Soc. 151, A1352 (2004). • 4.1 V • 170 mAh/g • σ<10-10 S/cm • Charged state evolves O2 at 150-200ΟC G. Chen, T.J. Richardson, J. Power Sources 195 (2010) 1221-1224. Shyue Ping Ong, Vincent L. Chevrier, Anubhav Jain, Geoffroy Hautier, Gerbrand Ceder

  4. Electronic Conduction by Polaron Migration • Small polaronconduction has been predicted by Maxisch et al.1 and verified experimentally by Zaghib et al.2 and Ellis et al.3in LiFePO4. • A polaron is a quasiparticle composed of a charge and its accompanying polarization field. Is the polaron migration barrier in LiMnPO4 significantly different from in LiFePO4? e- e- e- e- e- e- e- 1 T. Maxisch, F. Zhou, and G. Ceder, Physical Review B 73, 1-6 (2006). 2K. Zaghib, a. Mauger, J. B. Goodenough, F. Gendron, and C. M. Julien, Chemistry Of Materials 19, 3740-3747 (2007). 3 B. Ellis, L. K Perry, D H Ryan, and L F Nazar, Journal Of The American Chemical Society 128, 11416-22 (2006). Shyue Ping Ong, Vincent L. Chevrier, Anubhav Jain, Geoffroy Hautier, Gerbrand Ceder

  5. Computational Setup • 1 x 2 x 2 supercell • A-Type AFM configuration, i.e., alternating layers having opposite magnetic moments • Polaron hops occur within layer • -1 electron to LiMPO4supercell and perturb lattice to induce hole polaron formation (M3+) • +1 electron to MPO4 cell and perturb lattice to induce electron polaronformation (M2+) Shyue Ping Ong, Vincent L. Chevrier, Anubhav Jain, Geoffroy Hautier, Gerbrand Ceder

  6. GGA+U fails to localize polaron in LiMnPO4! No polaron localization in GGA+U! Mn2+ eg t2g Shyue Ping Ong, Vincent L. Chevrier, Anubhav Jain, Geoffroy Hautier, Gerbrand Ceder

  7. Hybrid functionals needed to achieve localization! Clear hole polaron state above Fermi level in HSE06! Mn2+ More universal treatment of self-interaction offered by HSE06 needed to treat the more strongly hybridized polaron in the Mn olivine! eg t2g LiFePO4 Hole Polaron Shyue Ping Ong, Vincent L. Chevrier, Anubhav Jain, Geoffroy Hautier, Gerbrand Ceder

  8. Polaronic Distortion • Polaron in Mn olivine • More strongly hybridized • Jahn-Teller active nature of Mn3+ • => larger polaronic distortion • => Deeper potential well to self-trap polaron LiFePO4 Hole Polaron LiMnPO4 Hole Polaron Shyue Ping Ong, Vincent L. Chevrier, Anubhav Jain, Geoffroy Hautier, Gerbrand Ceder

  9. Free Polaron Migration Barriers Shyue Ping Ong, Vincent L. Chevrier, Anubhav Jain, Geoffroy Hautier, Gerbrand Ceder

  10. Computational Setup • 1 x 2 x 2 supercell • A-Type AFM configuration, i.e., alternating layers having opposite magnetic moments • Polaron hops occur within layer • -1 electron to LiMPO4supercell and perturb lattice to induce hole polaron formation (M3+) • +1 electron to MPO4 cell and perturb lattice to induce electron polaronformation (M2+) Shyue Ping Ong, Vincent L. Chevrier, Anubhav Jain, Geoffroy Hautier, Gerbrand Ceder

  11. Bounded Polaron Migration Barriers • Bounded hole and electron polaron migration barriers in LiMPO4 and MPO4 are similar in both Mn and Fe cases. • Bounded polaron migration barriers are ≈75 x lower in Mn olivine than Fe olivine Shyue Ping Ong, Vincent L. Chevrier, Anubhav Jain, Geoffroy Hautier, Gerbrand Ceder

  12. Intrinsic Kinetic Limitations of LiMnPO4 See talk by Byoungwoo Kang tomorrow! • Our work supports experimental evidence of intrinsic kinetic limitations in LiMnPO4 compared to LiFePO4. • Lower conductivity in LiMnPO4 would imply much smaller particle sizes are necessary to achieve short diffusion lengths. • Heavy dependence of rate capability on particle size seen by Drezen. • Good performance achieved by Martha et al.* using 30-nm C-LiMnPO4 *S. K. Martha, B. Markovsky, J. Grinblat, Y. Gofer, O. Haik, E. Zinigrad, D. Aurbach, T. Drezen, D. Wang, G. Deghenghi, and I. Exnar, J. Electrochem. Soc. 156, A541 (2009). T. Drezen, N-H Kwon, P. Bowen, I. Teerlinck, M. Isono, and I. Exnar, J. Power Sources 174, 949-953 (2007). B. Kang and G. Ceder, J. Electrochem. Soc. 157, A808 (2010). Shyue Ping Ong, Vincent L. Chevrier, Anubhav Jain, Geoffroy Hautier, Gerbrand Ceder

  13. Predicting Thermal Stability from First Principles • Thermodynamic methodology developed in our earlier work (S. P. Ong, L. Wang, B. Kang, G. Ceder, Chemistry Of Materials 20 (2008) 1798-1807). • Equilibrating open systems wrt O2 • Normalized oxygen grand potential Negligible for solid phases S << NO2sO2 where Shyue Ping Ong, Vincent L. Chevrier, Anubhav Jain, Geoffroy Hautier, Gerbrand Ceder

  14. Oxygen Evolution vs Temperature for delithiated LiMnPO4 Exp: MnPO4decomposes to Mn2P2O7 at 150–200 OC1,2 S. P. Ong, A. Jain, G. Hautier, B. Kang, and G. Ceder, Electrochemistry Communications 12, 427-430 (2010). Exp : Fe7(PO4)6observed3 during LixFePO4 (x << 1) decomposition at 500–600 OC, and orthorhombic -> trigonaltransformation temperature ~ 600–700 OC.4,5 1S. Kim, J. Kim, H. Gwon, K. Kang, J. Electrochem. Soc. 156 (2009) A635. 2G. Chen, T.J. Richardson, J. Power Sources 195 (2010) 1221-1224. 3C. Delacourt, P. Poizot, J. Tarascon, C. Masquelier, Nature Materials 4 (2005) 254-260. 4S. Yang, Y. Song, P.Y. Zavalij, M.S. Whittingham, Electrochem. Comm. 4 (2002) 239-244. 5G. Rousse, J. Rodriguez-Carvajal, S. Patoux, C. Masquelier, Chem. Mater. 131 (2003) 4082-4090 Shyue Ping Ong, Vincent L. Chevrier, Anubhav Jain, Geoffroy Hautier, Gerbrand Ceder

  15. Why is delithiated MnPO4 less stable than delithiated FePO4? Oxidation State 2+ 3+ eg Mn t2g eg Fe t2g Fe3+ and Mn2+ have exchange-stabilized d5 configuration Shyue Ping Ong, Vincent L. Chevrier, Anubhav Jain, Geoffroy Hautier, Gerbrand Ceder

  16. Conclusions Shyue Ping Ong, Vincent L. Chevrier, Anubhav Jain, Geoffroy Hautier, Gerbrand Ceder

  17. Acknowledgements • Prof. GerbrandCeder • Collaborators • Vincent Chevrier, Anubhav Jain, GeoffroyHautier • Funding • BATT Program • US Department of Energy • National Science Foundation • Robert Bosch Company and Umicore Shyue Ping Ong, Vincent L. Chevrier, Anubhav Jain, Geoffroy Hautier, Gerbrand Ceder

  18. Thank you! • Publications • Polaron migration barriers: Shyue Ping Ong, Vincent L. Chevrier, and GerbrandCeder, Small Polaron Migration and Phase Separation in Olivine LiMnPO4and LiFePO4investigated using Hybrid Density Functional Theory– to be submitted shortly to Physical Review B • Thermal stability: Shyue Ping Ong, AnubhavJain, GeoffroyHautier, ByoungwooKang, and GerbrandCeder, Thermal stabilities of delithiated olivine MPO4 (M = Fe, Mn) cathodesinvestigated using first principles calculations, Electrochemistry Communications 12, 427-430 (2010). Shyue Ping Ong, Vincent L. Chevrier, Anubhav Jain, Geoffroy Hautier, Gerbrand Ceder

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