(23)Na NMR Studies of Na(x)CoO2 Cathode Materials.
Abstract
Two samples of oxidized sodium cobalt oxide, Na(x)CoO2, where x = 0.3 and 0.7, have been studied by variable-temperature wide-line (23)Na NMR. All spectra exhibit a substantially paramagnetic-shifted response characterized by 2nd-order quadrupole broadening and diamagnetic-shifted weaker response. The paramagnetic shifts are attributed to spins localized on cobalt ions. The 2nd-order quadrupole splitting is resolved for x = 0.7, whereas the lineshapes obtained for x = 0.3 do not show the resolution and indicate a more symmetric sodium environment and/or a greater degree of ion mobility. Lineshapes for the two compositions behave somewhat differently as the temperature is changed, although both samples exhibit gradual line-narrowing over the entire range (-150 to 100 deg C). Spin-lattice relaxation time measurements reflect the presence of inequivalent sodium environments with one distribution of sodium environments characterized by long relaxation times (10 ms - 200 ms) and another set of environments characterized by much shorter times (< 500 micro seconds). jg
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 26, 1996
- Accession Number
- ADA304871
Entities
People
- Lingyun Ding
- M. Doeff
- P. Stallworth
- S. Greenbaum
- Yong Ma
Organizations
- Hunter College