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Institut Charles Gerhardt – CNRS and Université Montpellier 2 (France)

The Origins of Voltage Hysteresis in Li-Ion Batteries :. Rémi KHATIB Marie-Liesse DOUBLET, Miran GABERŠČEK. Institut Charles Gerhardt – CNRS and Université Montpellier 2 (France) National Institute of Chemistry of Ljubljana (Slovenia) Remi.Khatib@univ-montp2.fr. www.energie-rs2e.com.

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Institut Charles Gerhardt – CNRS and Université Montpellier 2 (France)

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  1. The Origins of Voltage Hysteresis in Li-Ion Batteries : Rémi KHATIB Marie-Liesse DOUBLET, Miran GABERŠČEK. Institut Charles Gerhardt – CNRS and Université Montpellier 2 (France) National Institute of Chemistry of Ljubljana (Slovenia) Remi.Khatib@univ-montp2.fr • www.energie-rs2e.com

  2. OUTLINE • Introduction to Li-ion batteries • Electrochemistry of CoP • Bulk calculations, synthesis, characterization • New methodology surface and interface reactivity • Surface electrochemistry, Hysteresis • Conclusions / Perspectives

  3. Li-ION BATTERIES • Secondary (rechargeable) electrochemical devices Positive High-potential vs. Li+/Li0 4 ≤ V < 5 volts REDUCTION Negative Low-potential vs. Li+/Li0 0 < V ≤ 1 volt OXIDATION

  4. Li-ION BATTERIES • Secondary (rechargeable) electrochemical devices Positive High-potential vs. Li+/Li0 4 ≤ V < 5 volts OXIDATION Negative Low-potential vs. Li+/Li0 0 < V ≤ 1 volt REDUCTION

  5. Li-ION BATTERIES • Secondary (rechargeable) electrochemical devices Positive High-potential vs. Li+/Li0 4 ≤ V < 5 volts OXIDATION Negative Low-potential vs. Li+/Li0 0 < V ≤ 1 volt REDUCTION Energy stored depends on: - Working voltage G : Gibbs energy - Specific capacity: amount of Li exchanged per mass/volume unit.

  6. Li-ION BATTERIES How can we calculate a potential? A + nLi B

  7. Li-ION BATTERIES How can we calculate a potential? A + nLi B Multi-phases reaction Single phase reaction

  8. Li-ION BATTERIES How can we calculate a potential? A + nLi B Multi-phases reaction Single phase reaction

  9. Li-ION BATTERIES How can we calculate a potential? A + nLi B Multi-phases reaction Single phase reaction

  10. Li-ION BATTERIES How can we calculate a potential? A + nLi B V: independent of the state of charge or discharge

  11. Li-ION BATTERIES How can we calculate a potential? A + nLi B DFT (+U) 1 – 4 eV 10-5eV 3kBT V: independent of the state of charge or discharge

  12. Li-ION BATTERIES How can we calculate a potential? A + nLi B DFT (+U) 1 – 4 eV 10-5eV 3kBT V: independent of the state of charge or discharge

  13. Li-ION BATTERIES How can we calculate a potential? A + nLi B DFT (+U) 1 – 4 eV 10-5eV 3kBT V: independent of the state of charge or discharge VASP code Basis : Plane waves Functional : GGA-PBE 3D Translation

  14. Li-ION BATTERIES • Efficiency Energy provided by the battery Discharge

  15. Li-ION BATTERIES • Efficiency Energy to provide to the battery Charge

  16. Li-ION BATTERIES • Efficiency Energy lost DV

  17. Li-ION BATTERIES • Efficiency Energy lost DV Origins of DV: Kinetic → Polarization Thermodynamic → Hysteresis

  18. Li-ION BATTERIES Specific capacity 160 140 120 100 80 60 40 20 0 4.5 C 4.0 3.5 3.0 2.5 2.0 4.5 C/5 4.0 3.5 3.0 2.5 2.0 4.5 C/20 4.0 3.5 3.0 2.5 2.0 0.0 0.2 0.4 0.6 0.8 1.0 • Polarization = kinetic Masquelier C. et al., ECS Letters, 9, A352, 2006 Boyano I. et al., J. Power Sources, 195, 5351, 2010 Zhu Y. et al., J. Phys. Chem. C, 114, 2830, 2010

  19. Li-ION BATTERIES Specific capacity 160 140 120 100 80 60 40 20 0 4.5 C 4.0 3.5 3.0 2.5 2.0 4.5 C/5 4.0 3.5 3.0 2.5 2.0 4.5 C/20 4.0 3.5 3.0 2.5 2.0 0.0 0.2 0.4 0.6 0.8 1.0 • Polarization = kinetic Masquelier C. et al., ECS Letters, 9, A352, 2006 Boyano I. et al., J. Power Sources, 195, 5351, 2010 Zhu Y. et al., J. Phys. Chem. C, 114, 2830, 2010

  20. Li-ION BATTERIES Specific capacity 160 140 120 100 80 60 40 20 0 4.5 C 4.0 3.5 3.0 2.5 2.0 4.5 C/5 4.0 3.5 3.0 2.5 2.0 4.5 C/20 4.0 3.5 3.0 2.5 2.0 0.0 0.2 0.4 0.6 0.8 1.0 • Polarization = kinetic TROUVER UNE AUTRE IMAGE ET METTRE LA GITT AVANT. GITT Masquelier C. et al., ECS Letters, 9, A352, 2006 Boyano I. et al., J. Power Sources, 195, 5351, 2010 Zhu Y. et al., J. Phys. Chem. C, 114, 2830, 2010

  21. Li-ION BATTERIES MX (X = H, P, N, S, O, F) DV (Volt) H P N S O F • Hysteresis = thermodynamic MX+ nLi LinX + M0 Covalent M-X Ionic M-X Conversion materials: CoO, FeP, FeP2, FeP4, MgH2, CuF2… Bruce et al.,Angew. Chem. Int. Ed., 47, 2930, 2008

  22. CoP CHARACTERISTICS Li3P + Co0 CoP + 3Li Li3P Co0

  23. CoP CHARACTERISTICS Li3P + Co0 CoP + 3Li Ceramic route Stoichiometric amount of Co0 and red P Inert atmosphere (Ar) Temperature slope: 20 oC.h-1 5 days at 700 oC Liquid N2 quenched 1 mm SEM S. Boyanovet al., Chem. Mater. 2006, 18, 3531-3538.

  24. CoP CHARACTERISTICS Li3P + Co0 CoP + 3Li Ceramic route Stoichiometric amount of Co0 and red P Inert atmosphere (Ar) Temperature slope: 20 oC.h-1 5 days at 700 oC Liquid N2 quenched 1 mm SEM S. Boyanovet al., Chem. Mater. 2006, 18, 3531-3538.

  25. CoP CHARACTERISTICS Li3P + Co0 CoP + 3Li Ceramic route Stoichiometric amount of Co0 and red P Inert atmosphere (Ar) Temperature slope: 20 oC.h-1 5 days at 700 oC Liquid N2 quenched 1 mm SEM S. Rundqvist, Acta Chem. Scand., 14(9), 1961, 1960

  26. CoP CHARACTERISTICS Li3P + Co0 CoP + 3Li Ceramic route Stoichiometric amount of Co0 and red P Inert atmosphere (Ar) Temperature slope: 20 oC.h-1 5 days at 700 oC Liquid N2 quenched 1 mm SEM S. Rundqvist, Acta Chem. Scand., 14(9), 1961, 1960

  27. CoP CHARACTERISTICS Li3P + Co0 CoP + 3Li Ceramic route Stoichiometric amount of Co0 and red P Inert atmosphere (Ar) Temperature slope: 20 oC.h-1 5 days at 700 oC Liquid N2 quenched 1 mm New peaks after ball-milling SEM S. Rundqvist, Acta Chem. Scand., 14(9), 1961, 1960

  28. CoP CHARACTERISTICS Li3P + Co0 CoP + 3Li DFT CoP6octahedra edge-connected Paramagnetic at room temperature Ferromagnetic at very low temperature DFT+U E. Bekaertet al., J. Phys. Chem. C, 112(51):20481, 2008.

  29. CoP CHARACTERISTICS Li3P + Co0 CoP + 3Li Knight shift Pauli paramagnetism 31P NMR CoP6octahedra edge-connected Paramagnetic at room temperature Ferromagnetic at very low temperature DFT+U NMR: Zeeman effect used to characterize magnetic properties of a nucleus. E. Bekaertet al., J. Phys. Chem. C, 112(51):20481, 2008.

  30. CoP ELECTROCHEMISTRY How can we calculate a potential? A + nLi B DFT (+U) 1 – 4 eV Li3P Co0 CoP 10-5eV 3kBT V: independent of the state of charge or discharge

  31. CoP ELECTROCHEMISTRY How can we calculate a potential? A + nLi B DFT (+U) 1 – 4 eV Li3P Co0 CoP 10-5eV 3kBT V: independent of the state of charge or discharge

  32. T=0K BULK PHASE STABILITY DIAGRAM Li3P + Co0 CoP + 3Li ? Li3P Co0 CoP Boyanovet al., Chem. Mater., 18, 15, 2006 Boyanovet al., Chem. Mater., 21, 298, 2009

  33. T=0K BULK PHASE STABILITY DIAGRAM Li3P + Co0 CoP + 3Li ? Li3P Co0 CoP Boyanovet al., Chem. Mater., 18, 15, 2006 Boyanovet al., Chem. Mater., 21, 298, 2009

  34. T=0K BULK PHASE STABILITY DIAGRAM Li3P + Co0 CoP + 3Li ? Li3P Co0 CoP V3 V1 V2 3-steps Insertion / Conversion mechanism V1 (0.98 V): CoP + ½ Li  Li½CoP V2 (0.70 V): Li½CoP + ½ Li LiCoP V3 (0.41 V): LiCoP + 2Li  Li3P + Co0 Li0.5CoP LiCoP Boyanovet al., Chem. Mater., 18, 15, 2006 Boyanovet al., Chem. Mater., 21, 298, 2009

  35. CoP ELECTROCHEMISTRY CoP + 3Li Li3P + Co0 ?

  36. CoP ELECTROCHEMISTRY CoP + 3Li Li3P + Co0 ? C/n: 1Li exchanged per formula unit in n hours

  37. CoP ELECTROCHEMISTRY CoP + 3Li Li3P + Co0 ?

  38. CoP ELECTROCHEMISTRY CoP + 3Li Li3P + Co0 ?

  39. CoP ELECTROCHEMISTRY CoP + 3Li Li3P + Co0 ? Charge Discharge

  40. CoP ELECTROCHEMISTRY mm-sizedelectrode CoP + 3Li Li3P + Co0 ? 1 mm Electrode at the end of discharge: micro- or nano-scaled?

  41. CoP ELECTROCHEMISTRY mm-sizedelectrode CoP + 3Li Li3P + Co0 ? Partially charged electrode: what is the composition of “LixCoP”? 1 mm Electrode at the end of discharge: micro- or nano-scaled?

  42. CoP ELECTROCHEMISTRY mm-sizedelectrode CoP + 3Li Li3P + Co0 ? Partially charged electrode: what is the composition of “LixCoP”? 1 mm Electrode at the end of discharge: micro- or nano-scaled? • Techniques • SEM • XRD (in situ, semi in situ, ex situ) • Magnetometry (SQUID) • NMR (7Li, 31P) • EPR

  43. ”LixCoP” CHARACTERIZATION SEM Full discharged x=1 CoP 5 mm 5 mm 5 mm

  44. ”LixCoP” CHARACTERIZATION SEM In situ XRD Full discharged x=1 CoP • Similar results for others XRD • More material • No carbon • Longer acquisition time • CoP microsized reacts 5 mm 5 mm 5 mm

  45. ”LixCoP” CHARACTERIZATION mm-sizedelectrode CoP + 3Li Li3P + Co0 ? Partially charged electrode: what is the composition of “LixCoP”? 1 mm Electrode at the end of discharge: micro- or nano-scaled? • Techniques • SEM • XRD (in situ, semi in situ, ex situ) • Magnetometry (SQUID) • NMR (7Li, 31P) • EPR

  46. ”LixCoP” CHARACTERIZATION What do we expect for the end of the discharge? Co0 nanoparticles embedded into Li3P F Ferromagnetism NMR 2 Wickoff positions for Li d(7Li) = +0.4, +4.7 ppm 1 Wickoff positions for P d(31P) = -278 ppm SQUID magnetometer B. León et al., J. Electrochem. Soc., 153(10):A1829–A1834, 2006. S. Boyanovet al., Chem. Mat., 21(2):298–308, 2009.

  47. ”LixCoP” CHARACTERIZATION What do we expect for the end of the discharge? Co0 nanoparticles embedded into Li3P What do we expect for the end of the discharge? Co0 nanoparticles embedded into Li3P No coercitivity High MS F F Magnetization curve Evolution of the magnetization according to the field with a constant temperature Ferromagnetism SQUID magnetometer

  48. ”LixCoP” CHARACTERIZATION What do we expect for the end of the discharge? Co0 nanoparticles embedded into Li3P What do we expect for the end of the discharge? Co0 nanoparticles embedded into Li3P F F ZFC/FC curve Evolution of the magnetization according to the temperature with a constant field Magnetic order Ferromagnetism SQUID magnetometer

  49. ”LixCoP” CHARACTERIZATION What do we expect for the end of the discharge? Co0 nanoparticles embedded into Li3P What do we expect for the end of the discharge? Co0 nanoparticles embedded into Li3P No coercitivity High MS F F Magnetic order Ferromagnetism SQUID magnetometer Superparamagnetism: associated with nanoparticles of ferromagnetic compounds

  50. ”LixCoP” CHARACTERIZATION What do we expect for the end of the discharge? Co0 nanoparticles embedded into Li3P What do we expect for the end of the discharge? Co0 nanoparticles embedded into Li3P 7Li MAS-NMR NMR 2 Wickoff positions for Li d(7Li) = +0.4, +4.7 ppm 1 Wickoff positions for P d(31P) = -278 ppm 31P NMR B. León et al., J. Electrochem. Soc., 153(10):A1829–A1834, 2006. S. Boyanovet al., Chem. Mat., 21(2):298–308, 2009.

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