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McMaster University | Department of Chemistry

Event 

Title:
Leigh Spencer
When:
20.01.2010
Where:
ABB 163 -
Category:
Seminars & Colloquia

Description

Solid State Electrolytes for Li Ion Batteries

Leigh Spencer

 

Garnet and garnet-like structures have attracted great interest as candidates for solid state electrolytes in solid state lithium ion batteries.  It has been shown recently that 6/7Li NMR is a powerful tool for investigating Li+ dynamics in garnet structures such as Li5La3Nb2O12.1 Within this class of materials the garnet-like structure Li6BaLa2Ta2O12 exhibits higher ionic conductivity than the niobium analogues, at 4.0x10-5 S/cm at room temperature, due to its high Li+ mobility.  It is also unreactive against cathode materials, such as LiCoO2, up to and including 900ºC.2 This material had been previously investigated using powder X-ray diffraction and neutron diffraction, with the latter aiming to identify the lithium site occupancies, whether tetrahedral or octahedral.2,3 The occupancy of, and dynamics among these sites  remains an open question. We have studied this material using solid state 6/7Li MAS NMR to determine the crystallographic sites of Li+, and have also used variable temperature 6/7Li MAS NMR to observe the dynamics of Li+. In addition, iron containing garnet structures, such as La30Li22Fe6.4O67, have been studied. Two unique lithium sites have been observed, which is contrary to the single lithium site predicted by Mazza et al.4, who studied the material with powder X-ray diffraction. Analysis using X-ray powder diffraction, variable temperature 7Li MAS NMR, and 2D exchange MAS NMR has been employed to interpret the structure and dynamics of these novel materials.

1. van Wullen, L., Echelmeyer, T., Meyer, H.-W., Wilmer, D. Phys. Chem. Chem. Phys., 9, 2007, 3298-3303.

2. Thangadurai, V. Weppner, W. Journal of Power Sources, 142, 2005, 339-344

3. O’Callaghan, M. P., Cussen, E. J. Solid State Sciences, 10, 2008, 390-395

4. Mazza, D., Abbatista, F., Vallino, M. Journal of Less-Common Metals. 106, 1985, 277-285


 

DATE:             Wednesday, January 20, 2010

TIME:             1:30 p.m.

PLACE:            ABB 163

Venue

Venue:
ABB 163
Chemistry & Chemical Biology
McMaster Academic Planner