Edinburgh | May-16 | Ions that can Hop, Skip and Jump: Lithium Conduction in Disordered, Crystalline Solids
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Presenter : Eddie Cussen
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Edinburgh | May-16 | Ions that can Hop, Skip and Jump: Lithium Conduction in Disordered, Crystalline Solids
- 1. Ions that can Hop, Skip and Jump: Lithium Conduction in Disordered, Crystalline Solids Eddie Cussen Department of Pure and Applied Chemistry, The University of Strathclyde
- 2. Structure/Properties of Complex Oxides T / K Amplitudeofrelaxing componentofasymmetry Muon spin relaxation Magnetic Frustration 20 10 20 40 60 T / K Jahn Teller & Metal-Insulator Instabilities Ferromagnetism & magnetoresistance
- 3. Lithium ion conduction in Oxides • LixLa2/3-xTiO3-δ best crystalline oxide phase, σRT ≈ 10-3 S cm -1 • Perovskite is close packed structure; central interstice is filled • σ ≈ 10-6 S cm-1 for Pr and Nd analogues West et al, J. Mater. Chem., 1995, 5(11), 1807
- 4. LixLa2/3-xTiO3-δ Yashima et al, J. Am. Chem. Soc., 2005, 127, 3491 Li0.62La0.16TiO3 Structural Model (2005) Lithium metal causes reductive intercalation of Li+
- 5. Li+ Electrolytes • Fast Li+ conduction / no electronic conduction • (Electro)Chemical Stability • Ease of Preparation and Processing Li salt in liquid/amorphous polymer
- 6. High Performance Solid State Batteries • New solid electrolyte materials • Improved stability will allow new electrodes for higher voltages • Build these new materials into all solid state batteries • In situ characterisation during battery operation • Stabilise and characterise interface behaviour Lithium Conduction in New Crystalline Materials
- 7. Organic polymer electrolytes used in Li-ion batteries – safety issues Li-containing garnets combine high ionic conductivity (10-4 S cm-1) with desired electrochemical stability In conventional garnet, eight cations in two octahedral, three cubic and three tetrahedral sites, latter filled with Li Li-stuffed garnets as solid electrolytes Amores, Cussen, Corr et al.; J. Mater. Chem. A, 2016
- 8. Have reduced synthesis times and temps for Al-doped LLZO garnets from 36 h at 1230 °C to 1 h at 1000 °C Microwave synthesis of Li-stuffed garnets Rietveld analysis in conjunction with ICP and EDX reveals stoichiometry of Li6.5Al0.25La2.92Zr2O12 is obtained Amores, Cussen, Corr et al.; J. Mater. Chem. A, 2016
- 9. Li-stuffed garnets as solid electrolytes
- 10. Have reduced synthesis times and temps for Al-doped LLZO garnets from 36 h at 1230 °C to 1 h at 1000 °C Microwave synthesis of Li-stuffed garnets Rietveld analysis in conjunction with ICP and EDX reveals stoichiometry of Li6.5Al0.25La2.92Zr2O12 is obtained Amores, Cussen, Corr et al.; J. Mater. Chem. A, 2016
- 11. Spin-polarized positive muons stop at interstitial sites with large electronegativity, expected to be near the oxygens in the garnet lattice Li-diffusion in Li-stuffed garnets Thermally activated region Amores, Cussen, Corr et al.; J. Mater. Chem. A, 2016
- 12. Observe differences in Eact obtained from SR compared to EIS (0.55 eV) Li-diffusion in Li-stuffed garnets In EIS, resistance to Li-diffusion through grain-boundaries contributes to total resistance, increasing Eact for Li-conduction SR acts as local probe sensing mostly intra-grain diffusion, without extrinsic interference Z = R σ • Semicircles due to resistance to Li diffusion • Tail due to Pt blocking electrodes Amores, Cussen, Corr et al.; J. Mater. Chem. A, 2016
- 13. Filled Td Empty Td Disordered Structures Cussen, J. Mater. Chem, 2010 Lithium Mobility in Garnets
- 14. Lithium Mobility in Garnets 400 oC Li3Nd3Te2O12 Li4Nd3TeSbO12Li4.5Nd3Te0.5Sb1.5O12
- 15. Lithium Mobility in Garnets
- 16. • Li+ is the only mobile ion • Multiple sites with 4 – 6 coordination • Multiple hop distances 0.4 to 2.2 Å • Inter-Cation repulsion from short Li...Li distances 2.4 Å • A detailed, disordered & dynamic energy landscape Ion Movement is a Complex, Cooperative and Evolving Process Lithium Mobility in Garnets
- 17. • Li salt dissolved in e.g. polyethylene oxide • Structural studies of crystalline vs amorphous materials • Li+ motion faster in amorphous phase • Rotational motion of PEO portion facilitates Li+ migration Ion Conduction in polymer electrolytes
- 18. Ion Conductivity in PEO : NH4SCN 1000 / T ln(σT) crystalline amorphous Solid State Electrochemistry, Bruce, West, Shriver et al, 1995
- 19. Lithium Sulfate T < 575 oC T > 575 oC Tofield et al., J. Phys. C: Solid St. Phys., 13 (1980) 6441
- 20. T < 575 oC T > 575 oC Tofield et al., J. Phys. C: Solid St. Phys., 13 (1980) 6441 Lithium Sulfate
- 21. High T Li2SO4
- 23. • Inorganic, non framework, crystalline conductors • High degree of motion in majority of atoms • LiBH4 shows fast ion conduction > 109oC Target: RT conduction by chemical doping Alkali Metal Borohydrides
- 24. LiBH4 structure at room temperature Pnma distorted Wurtzite
- 25. LiBH4 structure at room temperature Pnma distorted Wurtzite
- 26. • Phase transition at 109oC gives a hexagonal structure • Li+ conduction increases from 10-5 up to 10-2 S cm-1 • Structure of the high temperature phase doubtful • Halide substitution can reduce the Tc Li+ conduction in LiBH4 M. Matsuo and S. Orimo. Adv. Energy Mater. 2011, 1, 161
- 27. LiBH4 – LiBr Phase Diagram
- 28. Li(BH4)1-xBrx Lithium Conductivity Ea = 0.52(2) to 0.64(1) eV
- 29. Li(BD4)0.67Br0.33 Structure • X-rays dominated by bromide scatter • Single P63mc phase • Isotopically enrich 7Li, 11B and D • Neutron diffraction using GEM • Multiple data banks • Require detailed data at low d-space Cascallana, Keen, Cussen & Gregory; Chem. Mater., 2015
- 30. Li(BD4)0.67Br0.33 Structure Cascallana, Keen, Cussen & Gregory; Chem. Mater., 2015
- 31. Li(BD4)0.67Br0.33 Structure Cascallana, Keen, Cussen & Gregory; Chem. Mater., 2015
- 32. Li(BD4)0.67Br0.33 Structure Cascallana, Keen, Cussen & Gregory; Chem. Mater., 2015
- 33. Li(BD4)0.67Br0.33 Structure Cascallana, Keen, Cussen & Gregory; Chem. Mater., 2015
- 34. Li(BD4)0.67Br0.33 Structure Cascallana, Keen, Cussen & Gregory; Chem. Mater., 2015
- 35. Li(BD4)0.684(4)Br0.316(4) • Disorder in: lithium position, BH4 orientation and BH4 vs Br position • Raman suggests regular, flexible BH4 with Td symmetry
- 36. Variable temperature neutron scattering 300 400 500 T / K
- 37. Li(BH4)1-xBrx Lithium Conductivity • Stabilise fast conducting phase to room temperature • Li+ mobility and BH4 - rotational disorder • Strong coupling between anion orientation and Li+ conduction Use ion mobility to access new, metastable Li+ conductors
- 38. Irene Cascallana Marco Amores Dr Hany El-Shinawi Dr Mike O’Callaghan Dr Thomas Yip Acknowledgements Prof. Duncan Gregory Dr Serena Corr Dr Jeremy Titman Prof. George Chen Dr David Keen ISIS Dr Ron Smith ISIS Dr Winfried Kockelmann ISIS Dr Peter Baker ISIS muons I15 beamline Diamond EPSRC
- 40. Preparation of Bromide doped LiBH4 • Ball milling : (1-x) LiBH4 + x LiBr Li(BH4)1-xBrx Followed by heating at 300OC for 5 hrs in N2
- 41. Preparation of Br-doped LiBH4 LiBH4 LiBr Li(BH4)1/2Br1/2 Li(BH4)2/3Br1/3 2θ / o Cu Kα Intensity/arbitrraryunits
- 42. Li0.56(2)H0.45(2)LaTiO4HLaTiO4 + 1/2LiOH.H2O RT Ion Exchange Yip & Cussen, Chem. Commun., 2010: Inorg. Chem., 2013
Hinweis der Redaktion
- Ions that can Hop, Skip and Jump: Lithium Conduction in Disordered, Crystalline Solids The conventional model of a solid crystal portrays atoms as immobilised on well defined positions in space. This regular structure is evident in the highly defined order and symmetries of the diffraction patterns obtained from crystalline materials. However, there are a number of crystalline solids where a subset of the atoms show a high degree of mobility. In some of these phases, ions are able to move at speeds approaching those in molten salts or solutions. This ion mobility may be associated with very substantial disorder in the lattice and dramatic changes in the diffraction properties of the crystal. We will present work on fast lithium conducting solids where the mobility of Li+ makes these potential solid state electrolytes for improved lithium batteries. In addition to synthesising new materials, we use a combination of neutron diffraction, impedance analysis and solid state NMR to build a full picture of the origins and properties of lithium transport through these structures. Biography Eddie Cussen studied for a first degree in Materials Chemistry at the University of Nottingham before obtaining his doctorate in the Electronic Properties of Mixed Metal Oxides from Oxford University. He then worked on the sorption properties of porous coordination polymers with Prof. Matt Rosseinsky at Liverpool University before being awarded a Royal Society University Research Fellowship. He initially held this at Nottingham before being appointed as Lecturer and then Senior Lecturer at Strathclyde University. His research is focussed on preparing new crystalline inorganic solids, usually oxides, in order to better understand important physical properties such as ion conduction, magnetic ordering behaviour, metal insulator transitions and magnetotransport effects. Particular focus is on the fast lithium conduction seen in the garnets and the emergence of new states of matter on frustrated magnetic lattices.
- Best conduction in oxides is LiLaTiO3 Problem of electronic conduction (all candidates have stability, electronic cond, etc.) Work in Aberdeen! Still lively debate in literature
- Would like to use inert, fully oxidised mechanically strong material i.e. not act as fuel, protect electrodes from shock OXIDES!
- Electrolytes – not just oxides, not ceramics, not just polymers. Need to use lots of technique, expertise.
- We have moved a long way from the simple “isolated hopping event” for ion transport....
- We might expect crystalline behaviour to give the best defined path for mobility. Actually DISORDER can be a useful tool to increase conductivity.
- Classic work on polyethylene oxide doped with salt.
- An extreme example of mobility through disorder..... Almost have a liquid state (entropy, enthalpy for phase change) – diffraction pattern is liquid-like. Simulated pattern shows Bragg scattering (and genuinely amorphous background...)
- Actual high tempreature data show lots of short range order is present giving non-Bragg scattering...
- Make by ball milling and need to keep low temperature. Air sensitive so not battery materials – but prototype and usefukl lessons.
- X-rays determine Br position BD4 not centred at same site BD4 is present in two orientations Refine anion ratio to value of Li splits over two positions
- fllow using x-ray diffraction Needs heating to complete the reaction (or longer miling) Note the Raman signatture. The tetrahedral unit goes from point group with 3 disticnt H positions to hexagonal with 3 identical and one different. Phonon density of states in the high temperature structure is exceptionally high at low energy in LiBH4. i.e. this is the cause of dissapearance of distincy peaks. It is not purely a thermal or a disorder effect. Maybe a problem of increasing disorder through higher symmetry.......
- No staging (same c-parameter) refine both H and Li positions from related compounds: proton in disordered hydroxyl group, Li neither sq.plan nor Td The position of the hydrogen atom was fixed at coordinates derived from full refinement against neutron diffraction data collected from HLaTiO4.10 The H/Li content was refined freely within the constraints of charge balance The proton is disordered over eight positions around each of the apical oxide anions at a short distance, 1.03 A ˚ , that is typical for protonated oxide. The lithium cations are coordinated to four oxide anions at 2.0131(13) A ˚ with a O–Li–O angle, 97.61, that is intermediate between tetrahedral and square planar geometries.