Jerzy E.Garbarczyk, Wojciech Wróbel Zakład Joniki Ciała Stałego Wydział Fizyki PW

1. Transport ładunku elektrycznego w amorficznych, nanokrystalicznych i kompozytowych przewodnikach elektronowych i jonowych Jerzy E.Garbarczyk, Wojciech Wróbel Zakład Joniki Ciała Stałego Wydział Fizyki PW

2. Motywacja Cel poznawczy Badanie transportu ładunku elektrycznego w mało poznanych formach fazy skondensowanej Cel aplikacyjny Zastosowania w urządzeniach do konwersji i magazynowania energii (baterie litowo-jonowe, ogniwa paliwowe, sensory gazowe, superkondensatory) Sympozjum Wydziału Fizyki 17 kwietnia 2008

3. Prezentacje Jerzy E.Garbarczyk „Nowe nanomateriały i kompozyty oparte na szklistych przewodnikach elektronowych i jonowych” Wojciech Wróbel „Korelacja między elektrycznymi i mechanicznymi właściwościami cieczy szkłotwórczych” Sympozjum Wydziału Fizyki 17 kwietnia 2008

4. Novel nanomaterials and composites based on electronic and ionic conductive glasses

5. Outline • Advantages and disadvantages of ionic and electronic conductive glasses • Novel nanomaterials based on lithium-vanadate-phosphate (LVP)glasses • Novel nanomaterials based on lithium-iron-phosphate (LFP) glasses • Novel composites based on ionically conductive glasses • Summary

6. Advantages and disadvantages of conductive glasses Advantages • simple processing • possibility of forming various shapes • isotropy and homogeneity • absence of grain boundaries • high ionic conductivity at room temperature (up to 10-2 S/cm for AgI – based conducting glasses) • high electronic conductivity at above 300ºC (up to 10-3 S/cm for vanadia – rich glasses) • inherent ability to nanocrystallization (this study) • possibility of considerable modification of the composition and electrical properties

7. Example: vanadia-based glasses Mixed ionic-electronic conductivity in systems: Li2O - V2O5 - P2O5(Li+/e-) AgI - Ag2O - V2O5 - P2O5(Ag+/e-) V2O5 – main glass former, source of electronic conductionvia V4+ → V5+ hopping of small polarons P2O5 – supporting glass former Li2O – glass modifier, source of mobile Li+ ions Ag2O – glass modifier,source of mobile Ag+ ions AgI – dopant, main source of mobile Ag+ ions

8. or Model of the electrical charge transport in Li2O-V2O5-P2O5 glasses

9. or Model of the electrical charge transport in Li2O-V2O5-P2O5 glasses

10. or Model of the electrical charge transport in Li2O-V2O5-P2O5 glasses

11. or Model of the electrical charge transport in Li2O-V2O5-P2O5 glasses

12. or Model of the electrical charge transport in Li2O-V2O5-P2O5 glasses

13. or Model of the electrical charge transport in Li2O-V2O5-P2O5 glasses

14. or Model of the electrical charge transport in Li2O-V2O5-P2O5 glasses

15. or Model of the electrical charge transport in Li2O-V2O5-P2O5 glasses

16. or Model of the electrical charge transport in Li2O-V2O5-P2O5 glasses

17. electronic ionic mixed V2O5-rich glasses Isotherms of the total electrical conductivity in Li2O-V2O5-P2O5 glasses P.Jozwiak, J.Garbarczyk, Solid State Ionics 176 (2005) 2163 H.Takahashi, T.Karasawa, T.Sakuma, J.E.Garbarczyk, ICPSSI-2, Yokohama, 2007

18. Total electrical conductivity at 100°C vs. composition in AgI-Ag2O-V2O5-P2O5 glasses ionic electronic J.E.Garbarczyk, P.Machowski et al. Mol.Phys.Rep. 35 (2003) 139.

19. Total electrical conductivity at 100°C vs. composition in AgI-Ag2O-V2O5-P2O5 glasses ionic ionic electronic electronic J.E.Garbarczyk, P.Machowski et al. Mol.Phys.Rep. 35 (2003) 139.

20. Advantages and disadvantages of conductive glasses (cont.) Disadvantages • metastability • composition and structure less known than those of the crystalline materials • low glass transition temperature of the best ion conductive glasses (for AgI-doped glasses 60°C <Tg < 100°C) • low fracture toughness • moderate electronic conductivity at 20°C of glassy cathode materials

21. Aims of our studies • preparation of new nanomaterials derived from conductive glasses exhibiting better electrical properties and thermalstability than the initial glasses • preparation of new glassy-crystalline composites exhibiting improved mechanical properties compared to the glasses

22. Novel nanomaterials based on lithium-vanadate-phosphate (LVP) glasses It is known that nanostructured materials exhibit attractive properties, often dramatically different than those of the crystalline or amorphous counterparts. • Effect of nanocrystallization on ionic conductivity St. Adams, K.Hariharan, J.Maier, Solid State Ionics 86-88 (1996) 503. AgI-rich glasses of the system AgI-Ag2O-MxOy • Effect of nanocrystallization on electronic and mixed conductivity J.E.Garbarczyk, P.Jozwiak et al. Solid State Ionics 175 (2004) 691. V2O5-rich glasses of the system Li2O-V2O5-P2O5 a) 15Li2O·70V2O5·15P2O5 b) 90V2O5·10P2O5

23. DSC Nanocrystallization of the90V2O5∙10P2O5 glass

24. SEM picture of a 90V2O5∙10P2O5sample after nanocrystallization at Tc ≈ 340°C

25. visible nanocrystallites of V2O5 covered by a glassy phase 20 nm SEM picture of a 90V2O5∙10P2O5sample after nanocrystallization at Tc ≈ 340°C

26. SEM picture and XRD pattern of a 90V2O5∙10P2O5 sampleafter massive crystallization at 540°C ● - orthorhombic V2O5

27. SEM picture of a 90V2O5∙10P2O5sampleafter massive crystallization at 540oC (another fragment) orthorhombic V2O5 crystallites

28. Discussion of the results on vanadia-based nanomaterials Mott theory of electron hopping in disordered systems for T > q/ 2 q – Debye temperature • R – average distance between hopping centers • C – fraction of hopping sites occupied by electrons • N – concentration of hopping centres • – inverse localization length of the electron wave function rp – radius of a small polaron

29. 20 nm Discussion of the results on vanadia-based nanomaterials Samples after nanocrystallization V2O5

30. higher concentration of V4+ -V+5pairs 20 nm Discussion of the results on vanadia-based nanomaterials Samples after nanocrystallization V2O5

31. high concentration of V4+ -V+5pairs 20 nm Discussion of the results on vanadia-based nanomaterials Samples after nanocrystallization + easy conduction path V2O5 – „Easy conduction paths” – interface regions between nanocrystallites and glassy phase. Higher concentration of V4+-V5+ pairs in these regions than inside grains.

32. Discussion of the results (cont.)Sample after massive crystallization There is no intermediate glassy phase. The electrical transport between grains is partly blocked by the presence of grain boundaries.

33. Novel nanomaterials based on lithium-iron-phosphate (LFP) glasses • Crystalline lithium-iron-phosphates (olivines) • Nanocrystallization of glassy samples - SEM Cooperation with Prof. Christian Julien, Univ. P.et M.Curie, Paris, France (local structure) A.Ait Salah, P.Jozwiak, J.Garbarczyk, Ch.Julien et al. Journal of Power Sources140 (2005) 370.

34. Związki interkalowane - przykłady Oliwiny i związki pokrewne

35. Crystalline lithium-iron-phosphates Crystalline olivine-type phases - LiFePO4 and FePO4 as well as LixFePO4 solid solutions - are under intensive studies worldwide as the most competitive cathode materials for Li-ion rechargeable batteries. These cathode materials are: • highly stable (thermally and electrochemically), • inexpensive, • environment –friendly. Furthermore they exhibit: • high specific capacity (170 mAh/g), • high discharge voltage (3.5 V vs. Li).

36. Crystalline lithium-iron-phosphates Crystalline olivine-type phases - LiFePO4 and FePO4 as well as LixFePO4 solid solutions - are under intensive studies worldwide as the most competitive cathode materials for Li-ion rechargeable batteries. These cathode materials are: • highly stable (thermally and electrochemically), • inexpensive, • environment –friendly. Furthermore they exhibit: • high specific capacity (170 mAh/g), • high discharge voltage (3.5 V vs. Li). Unfortunately they have one serious deficiency – very low electrical conductivity - ca. 10-10 S·cm‑1 at 25°C.

37. Crystalline olivines (cont.) Many efforts have been undertaken to improve their electrical properties by: • introduction of carbon additives, • doping with supervalent cations, • various synthesis routes. Our alternative approach – nanocrystallization of glassy analogs of olivines: • step 1: preparation of vitreous analogs of these materials, • step 2: turning these glasses into nanomaterials by an appropriate thermal treatment.

38. Electrical properties after partial nanocrystallization (sample of x = 0)

39. SEM picture after partial nanocrystallization for sample of x = 0

40. Electrical properties after partial nanocrystallization (sample of x = 0.4) σt(50°C)=7.6∙10-8S/cm ≈4 times σt(50°C)= 1.8∙10-8S/cm σt(530°C)=1.1∙10-2S/cm

41. SEM micrograph after crystallizationfor sample of x = 0.4

42. SEM micrograph after crystallizationfor sample of x = 0.4

43. Novel composites based on ionically conductive glasses Motivation Ag+ - ion conductive glasses exhibit high electrical conductivity (up to 10-2 S·cm-1 at 25°C), but some of their mechanical properties may cause problems with samples machining (e.g. cutting and polishing) and limit eventual prospective applications. In order to minimize this drawback we propose new composites based on silver-ion conductive glasses.

44. Novel composites based on ionically conductive glasses (cont.) Glassy components: AgI-Ag2O-B2O3 AgI-Ag2O-P2O5 AgI-Ag2O-V2O5 Ceramic powder components: Diamond (1-2 µm) a-Al2O3 (2 µm) ZrO2(1 and/or 10 µm) Composites prepared in 50 - 50 % vol fractions B2O3, P2O5, V2O5 – glass formers Ag2O – glass modifier AgI – dopant

45. High-pressure route of preparation of the composites Facility at the Institute of High Pressure Physics,Polish Academy of Sciences, Warsaw

46. 100-250°C 100-200°C 3-8 GPa High-pressure route of preparation of the composites (cont.)

47. SEM and XRD studies after annealing at 200°C as-prepared Obrazek SEM (fosforanowe z diamentem, boranowe z alumina) Glass: 40AgI·30Ag2O·30P2O5 Diamond powder (1-2 mm) Synthesis: p = 3 GPa, T = 250°C M.Zgirski, J.Garbarczyk et al., Solid State Ionics, 176 (2005) 2141

48. Glass Al2O3 Al2O3 SEM studies (cont.) 50AgI·33Ag2O·17B2O3 : a-Al2O3 (2 mm)-a phase view

49. SEM studies (cont.) ZrO2 55AgI·30Ag2O·15B2O3 : ZrO2 (1 mm)-a phase view

50. E=0.34 eV Tg glass s200=1.6·10-2 S·cm-1 E=0.54 eV 40AgI·30Ag2O·30P2O5 : diamond s27=1·10-4 S·cm-1 Electrical properties of compositesabove room temperature