1 / 18

Shyue Ping Ong, Anubhav Jain, Geoffroy Hautier , Byoungwoo Kang, Gerbrand Ceder

Predicted Thermal ( In)stability of Olivine LiMPO 4 Cathodes from First Principles Phase Diagrams. Shyue Ping Ong, Anubhav Jain, Geoffroy Hautier , Byoungwoo Kang, Gerbrand Ceder. Importance of Thermal Stability. Thermal runaway is a major safety issue in rechargeable batteries

swain
Download Presentation

Shyue Ping Ong, Anubhav Jain, Geoffroy Hautier , Byoungwoo Kang, Gerbrand Ceder

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Predicted Thermal (In)stability of Olivine LiMPO4 Cathodes from First Principles Phase Diagrams Shyue Ping Ong, Anubhav Jain, GeoffroyHautier, Byoungwoo Kang, GerbrandCeder

  2. Importance of Thermal Stability • Thermal runaway is a major safety issue in rechargeable batteries • Starts with an overheating event (e.g. caused by an internal or external short) which causes the charged cathode to release oxygen. • Oxygen combusts electrolyte with evolution of heat and ultimately leads to fire. What if the Starship Enterprise ran on current Li batteries? • Current Li battery technology based on LiCoO2 has significant safety issues • Improving thermal stability is a key criteria for next-generation Li battery materials, especially for large scale applications such as HEV S. P. Ong, A. Jain, G. Hautier, B.W. Kang, G. Ceder

  3. Olivine Cathodic Thermal (In)stability Recent expt. evidence1,2 showed that charged/delithiated LiMnPO4 is much less thermally stable (decomposition temperature ~ 150-200ΟC) than LiFePO4 (~500ΟC). 2G. Chen, T.J. Richardson, J. Power Sources 195 (2010) 1221-1224. 1S. Kim, J. Kim, H. Gwon, K. Kang, J. Electrochem. Soc. 156 (2009) A635. • Other evidence suggests that other higher voltage olivines (e.g. LiCoPO4) have even worse thermal stability than LiMnPO4. N.N. Bramnik, K. Nikolowski, D.M. Trots, H. Ehrenberg, Electrochemical And Solid-State Letters 11 (2008) A89. S. P. Ong, A. Jain, G. Hautier, B.W. Kang, G. Ceder

  4. First Principles Oxygen Grand Potential Phase Diagrams • Thermodynamic methodology developed in our earlier work (S. P. Ong, L. Wang, B. Kang, G. Ceder, Chem. Mater., 20 (2008) 1798-1807). • Equilibrating open systems wrt O2 • Normalized oxygen grand potential S << NO2sO2 Negligible for solid phases where μO2T @ fixed pO2 S. P. Ong, A. Jain, G. Hautier, B.W. Kang, G. Ceder

  5. Phase Diagram Construction From spin-polarized GGA+U calculations with PAW pseudopotentials(fitted Ueffective= 3.9 and 4.0eV forMn and Fe respectively 1) Free parameter 1 L. Wang, T. Maxisch, G. Ceder, Phys. Rev. B 73 (2006) 1–6. S. P. Ong, A. Jain, G. Hautier, B.W. Kang, G. Ceder

  6. Phase Diagrams at T=25OC S. P. Ong, A. Jain, G. Hautier, B.W. Kang, G. Ceder

  7. Phase Diagrams at T=370OC MnPO40.5 Mn2P2O7 + 0.25 O2 S. P. Ong, A. Jain, G. Hautier, B.W. Kang, G. Ceder

  8. Phase Diagrams at T=1230OC FePO40.167 Fe3(P2O7)2 + 0.167 Fe3(PO4)2 + 0.167 O2 S. P. Ong, A. Jain, G. Hautier, B.W. Kang, G. Ceder

  9. Phase Diagrams at T=1390OC FePO40.5 Fe2P2O7 + 0.25 O2 S. P. Ong, A. Jain, G. Hautier, B.W. Kang, G. Ceder

  10. Oxygen Evolution vs Temperature for delithiated LiFePO4 • Non-equilibrium path.Delithiated FePO4 begins to decompose at 700OC evolving 0.1 mol of O2per mol of charged cathode (c.c.) • Equilibrium path.Delithiated FePO4 decomposes at 1230OC, evolving 0.167 mol of O2per mol of c.c. • Expt. evidence points to some degree of non-equilibrium decomposition • Fe7(PO4)6 observed1 during LixFePO4 (x << 1) decomposition at 500–600 OC • Stability investigations2,3 showed that orthorhombic->trigonal transformation temperature ~ 600–700 OC 1 C. Delacourt, P. Poizot, J. Tarascon, C. Masquelier, Nature Materials 4 (2005) 254-260. 2 S. Yang, Y. Song, P.Y. Zavalij, M.S. Whittingham, Electrochem. Comm. 4 (2002) 239-244. 3 G. Rousse, J. Rodriguez-Carvajal, S. Patoux, C. Masquelier, Chem. Mater. 131 (2003) 4082-4090. S. P. Ong, A. Jain, G. Hautier, B.W. Kang, G. Ceder

  11. Oxygen Evolution vs Temperature for delithiated LiMnPO4 • Delithiated MnPO4 decomposes at 370OC evolving 0.25 mol of O2per mol of c.c. • Predicted decomposition products and temp. compare well with the exp. results of Kim et al.1 and Chen and Richardson2 (MnPO4 decomposes to Mn2P2O7 at 150–200 OC) • Temp. typically overestimated by ~100-200OC, possibly due to presence of reducing carbon or electrolyte in exp. and inherent errors in our approximations 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. S. P. Ong, A. Jain, G. Hautier, B.W. Kang, G. Ceder

  12. Why is delithiated MnPO4 less stable than delithiated FePO4? Oxidation State 2+ 3+ eg Stability range of LiMnPO4 Fe t2g Stability range of LiFePO4 eg Mn t2g • LiMnPO4 stable over wider range (-0.56eV<μO2<-7.02eV) than LiFePO4 (-2.36eV<μO2<-6.24eV) • Lower temperatures necessary for synthesis of LiMnPO4 • Reduction of LiMnPO4 more difficult Fe3+ and Mn2+ have exchange-stabilized d5 configuration S. P. Ong, A. Jain, G. Hautier, B.W. Kang, G. Ceder

  13. Thermal Stability of Other Olivine Cathodes • Charged states of higher voltage olivines, LiCoPO4 (4.8V) and LiNiPO4 (> 5V), have even worse predicted thermal stability than LiMnPO4! • Delithiated CoPO4 and NiPO4 are both predicted to be unstable at room temperature and evolves 0.25 mol of O2per mol of charged cathode (c.c.) S. P. Ong, A. Jain, G. Hautier, B.W. Kang, G. Ceder

  14. Relationship between Voltage and Thermal Stability • Huggins1 presented in 2009 on a possible relationship between voltage of cathode and the equilibrium partial pressure of oxygen (measure of thermodynamic stability) • But analysis was limited to conversion voltages, and a few simple oxide systems With the developed methodology + large computing resources + our in-house analysis software, we can do the same analysis on a much grander scale for intercalation compounds! 1R.A. Huggins, ECS Transactions 16 (2009) 37-47. S. P. Ong, A. Jain, G. Hautier, B.W. Kang, G. Ceder

  15. High-throughput Li Battery Material Search • Generally, higher voltage  Worse thermal stability • BUT new polyanion structures potentially achieve a better tradeoff between voltage and thermal stability. • Borates and silicates seem to offer the best voltage to thermal stability performance. Reproduced with permission from high-throughput project set up by A. Jain, G. Hautier, S. P. Ong, et al. S. P. Ong, A. Jain, G. Hautier, B.W. Kang, G. Ceder

  16. Conclusions • Grand potential phase diagram construction allows us to predict the thermal stability of cathodes • Predicted decomposition temperatures and products agree fairly well with experimental results • Relative instability of MnPO4 as compared to FePO4 may be explained by the relative stabilities of the M3+ and M2+ states as predicted by ligand field theory • Thermodynamic methodology + high-throughput screening environment provides a basis for multi-faceted material design • Published in S.P. Ong, A. Jain, G. Hautier, B. Kang, G. Ceder, Electrochem. Comm. 12 (2010) 427-430. S. P. Ong, A. Jain, G. Hautier, B.W. Kang, G. Ceder

  17. Acknowledgements • Collaborators • Anubhav Jain • GeoffroyHautier • Byoungwoo Kang • Advisor • GerbrandCeder • Funding from • BATT Program under Contract DE-AC02-05CH11231, • US Department of Energy under Contract No. DE-FG02-05ER46253 and DE-FG02-97ER25308 • NSF under Grant No. DMR-0606276. • Others • Robert Bosch Company and Umicore for their support, and Chris Fischer, Tim Mueller, and Charles Moore for their assistance in the development of the high-throughput battery screening environment. S. P. Ong, A. Jain, G. Hautier, B.W. Kang, G. Ceder

  18. Thank you.

More Related