Oxygen Nonstoichiometry in Li–Mn–O Spinel Oxides: A Powder Neutron Diffraction Study

✍ Scribed by P. Strobel; F. Le Cras; L. Seguin; M. Anne; J.M. Tarascon

• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 400 KB
• Volume: 135
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1997.7611

✦ Synopsis

Neutron powder diffraction has been carried out on two series of Li-Mn-O samples with spinel structure, which have been shown to lose oxygen with respect to initial stoichiometric spinels: (i) Li 1.05 Mn 2 O 4 quenched from 800 or 925°°C, (ii) ''Li 1.33 Mn 1.67 O '' (nominal) treated with ammonia gas at 200°°C. The structural refinements unambiguously show that both 925°°C quenching and low-temperature ammonia treatment induce oxygen vacancies in the spinel lattice. However, the mechanism of oxygen loss is markedly different between quenchings at 800 and 925°°C. While the latter actually corresponds to the introduction of anionic vacancies at constant cation composition, the former is due to a rearrangement of the Li/Mn ratio in the spinel phase and the formation of an additional lithium-rich phase Li 2 MnO 3 . The presence of vacancies induce a significant increase in atomic displacement parameters of oxygen.