Powell, A.S., Stoeva, Z., Smith, R.I., Gregory, D.H. and Titman, J.J. (2011) Structure, stoichiometry and transport properties of lithium copper nitride battery materials: combined NMR and powder neutron diffraction studies. Physical Chemistry Chemical Physics, 13(22), pp. 10641-10647. (doi: 10.1039/C1CP20368A)
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Publisher's URL: http://dx.doi.org/10.1039/C1CP20368A
Abstract
A combined NMR and neutron diffraction study has been carried out on three Li<sub>3−x−y</sub>Cu<sub>x</sub>N materials with <i>x</i> = 0.17, <i>x</i> = 0.29 and <i>x</i> = 0.36. Neutron diffraction indicates that the samples retain the P6/mmm space group of the parent Li<sub>3</sub>N with Cu located only on Li(1) sites. The lattice parameters vary smoothly with <i>x</i> in a similar fashion to Li<sub>3−x−y</sub>Ni<sub>x</sub>N, but the Li(2) vacancy concentration for the Cu-substituted materials is negligible. This structural model is confirmed by wideline 7Li NMR spectra at 193 K which show three different local environments for the Li(1) site, resulting from the substitution of neighbouring Li atoms in the Li(1) layer by Cu. Since the Cu-substituted materials are only very weakly paramagnetic, variable temperature 7Li wideline NMR spectra can be used to measure diffusion coefficients and activation energies. These indicate anisotropic Li<sup>+</sup> diffusion similar to the parent Li<sub>3</sub>N with transport confined to the [Li<sub>2</sub>N] plane at low temperature and exchange between Li(1) and Li(2) sites dominant at high temperature. For the intra-layer process the diffusion coefficients at room temperature are comparable to Li<sub>3</sub>N and Li<sub>3−x−y</sub>Ni<sub>x</sub>N, while <i>E</i><sub>a</sub> decreases as <i>x</i> increases in contrast to the opposite trend in Ni-substituted materials. For the inter-layer process <i>E</i><sub>a</sub> decreases only slightly as <i>x</i> increases, but the diffusion coefficients at room temperature increase rapidly with <i>x</i>.
| Item Type: | Articles |
|---|---|
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Gregory, Professor Duncan |
| Authors: | Powell, A.S., Stoeva, Z., Smith, R.I., Gregory, D.H., and Titman, J.J. |
| Subjects: | Q Science > QD Chemistry |
| College/School: | College of Science and Engineering > School of Chemistry |
| Journal Name: | Physical Chemistry Chemical Physics |
| Publisher: | Royal Society of Chemistry |
| ISSN: | 1463-9076 |
| ISSN (Online): | 1463-9084 |
| Published Online: | 01 January 2011 |
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