Development of Novel Lithium Salts for Battery Applications

1. Development of Novel Lithium Salts for Battery Applications

2. Outline of the presentation • Introduction – searching for new salts for lithium batteries • Synthesis and characterization of novel family of organic covalent lithium salts • Properties of polymer and liquid electrolytes containing newly developed salts: • conductivity • lithium transference number • formation of ionic aggregates • electrochemical stability • performance in lithium batteries • Conclusions

3. Anions: • Control dissociation and conductivity • Control transport numbers t+ /t- • are an important part of SEI build-up at +/- electrodes • Control aluminium corrosion

4. ClO4- BF4- Explosive ! Toxic ! PF6- AsF6- SbF6- Classics… Tendency to décompose according to equilibrium: LiBF4  BF3+ <LiF> LiPF6  PF5 + <LiF> Fast reaction above 80°C  Destruction of electrolyte and interfaces

5. Conceptual approach to anion design • “O” is not a favorable building block: Strong Li—O interactions  ion pairing, ≠ ClO4-, BOB- • “N, C” are favorable: Weak interactions Li—N but easy oxidation If O present, F or CnF2n+1 is required

6. Stability Domains Li metal Fluorinated anions Non fluorinated anions

7. Hückel anions… Aromaticity 4n + 2 «  » electrons pKA = 10-60 pKA = 10-20 X = N, C-CN, CRF, S(O)RF Gain of > 1 eV by resonance See P. Johansson et alPhysical Chemistry Chemical Physics, volume 6, issue 5, (2004).

8. LiDCTA DCTA Stable to 3.8 V (La Sapienza, KZ)inexpensive Gives quite fluid ILs

9. Most Stable Lithium Imidazole Configurations 1.93 Å 1.87 Å 1.88 Å 1.92 Å LiTDI LiPDI B3LYP/6-311+G(d) Scheers et al. 2009

10. Gas Phase Ion Pair Dissociation Energies Ion pair (g) Li+ (g) + Anion- (g) LiTDI < LiPDI < LiDCTA < LiTFSI < LiPF6 MP2/6-31G(d) LiTDI LiPDI LiDCTA LiTFSI LiPF6 Scheers et al. 2009

11. LiTDI (2-trifluoromethyl-4,5-dicyanoimidazole lithium salt) - Easy, low‑demanding, inexpensive, one‑step, high yield syntheses; - Salts are pure, stable in air atmosphere, non‑hygroscopic, stable up to 250°C, easy to handle;

12. New salts

13. Conductivity in PEO SS / PEO20LiX / SS cooling scan LiDCTA LiPDI LiTDI

14. LiHDI-PEO Conductivity 1:25 Ea=76.4 kJ∙mol-1 1:50 Ea=121.8 kJ∙mol-1

15. PEO20LiTDI PEO20LiPDI Hot-Pressing PEO20LiTDI PEO20LiPDI PEO20LiBOB/ LiBF4 Hot-Pressing PEO20LiDCTA Hot-Pressing PEO20LiCF3SO3+ ZrO2SA Casting

16. Anodic stability Li / PEO20LiX / Super P LiDCTA LiPDI LiTDI

17. Interphase resistance - PEO Li / PEO20LiX / Li LiTDI LiDCTA LiPDI

18. Interphase resistance - PEO Li / PEO20LiX / Li LiPDIa LiPDIb LiTDIa LiTDIb LiDCTAa LiDCTAb

19. Cycling behaviour

20. Rate capability (PEO) % of capacity at C/20

21. Rate capability (PEO) % of capacity at C/20

22. LiTDI-PEGDME500 Conductivity

23. Transference numbers in PEGDME 500

24. Cation transference number vs. Ionic conductivity (PEGDME 500)

25. LiTDI-PEGDME500Stability vs. Lithium against time

26. LiTDI-PC Conductivity

27. LiHDI-PC Conductivity

28. LiTDI-PC Molar Conductivity

29. LiHDI-PC Molar Conductivity

30. LiTDI-PC Fuoss-Kraus formalism association estimation

31. LiHDI-PC Fuoss-Kraus formalism association estimation

32. Transference Numbers in PC

33. Salts-PC Stability vs. Lithium

34. LiTDI Conductivity in EC:DMC

35. Conductivities (20°C)

36. Ragone Signature

37. Anodic limit (Pt, EC-DMC)

38. Anodic limit (Al, EC-DMC)

39. Charge profile 4.3 V cut-off, Al collector

40. Cycling LiMn2O4 4.3 V (EC-DMC) Swagelok cell , Al plunger

41. New imidazole-derived salts • Easy, low‑demanding, inexpensive, one‑step, high yield syntheses; • Salts are pure, stable in air atmosphere, non‑hygroscopic, stable up to 250°C, easy to handle; • 20°C ionic conductivity exceeds: 10‑3 S∙cm-1 in PC, 10‑4 S∙cm‑1 in PEGDME500 10‑6 S∙cm‑1 in PEO (10‑4 S∙cm‑1 at 40°C) 6 mS∙cm‑1 in EC:DMC • T+ at ionic conductivity maximum reaches: 0.45 in PC, 0.40 in EC-DMC, 0.25 in PEGDME500 (but overall max 0.62); • Stable over time against Li; • Stable up to 4.4 V vs. Li against metallic lithium anode; • Stable up to 5.0 V vs. Li against aluminum; • Much smaller association rate than commercially available salts;

42. Research team working on new salts Presentation of research team working on new lithium salts: Warsaw University of Technology: - L. Niedzickiand W. Wieczorek – characterization of salts and low molecular weight polyether electrolytes - J. Prejzner, P. Szczeciński, M. Bukowska - synthesis of new salts - Z. Żukowska – spectroscopic studies Universite de Picardie Jules Verne, Laboratoire de Reactivite et de Chimie des Solides - S. Grugeon, S. Laruelle - characterization of solid polymeric electrolytes, studies of electrochemical stability and battery performance - and M. Armand – development of new salt systems Faculty of Chemistry, University of Rome, “ La Sapienza - S. Panero, P. Reale and B. Scrosati, - characterization of solid polymeric electrolytes; conductivity, transference numbers and electrochemical stability Department of Applied Physics, Chalmers University of Technology, - J. Scheers, P. Johansson, P. Jacobsson – modeling and spectroscopic studies

43. For inquiries about buying LiTDI(lithium 4,5-dicyano-2-(trifluoromethyl)imidazolate)please contact:Leszek Niedzickiasalm@ch.pw.edu.pl