STRUCTURE OF HOLLOW IRON OXIDE NANOPARTICLES DOPPED WITH MOLYBDENUM STUDIED BY XAFS AND SAXS

P. CECILIA DOS SANTOS CLARO; LISANDRO GIOVANETTI; LEANDRO ANDRINI; FÉLIX G. REQUEJO; BONIL KOO; ELENA V. SHEVCHENKO

Cancun

Congreso; XXII INTERNATIONAL MATERIALS RESEARCH CONGRESS 2013; 2013

Sociedad Mexicana de Materiales and The Materials Research Society (MRS)

The large capacity resulting from reducing iron oxide to iron is promising for lithium battery anodes; however, this conversion during the electrochemical cycling is accompanied by fading of the electrode performance due to material pulverization and subsequent loss of electrical contacts between the active material and current collector. On the other hand, cycling of iron oxide-based electrodes in the high voltage range where only intercalation of Li ions occurs has been recently found to be promising to design cathodes [1]. The unique nature of hollow metal oxide nanoparticles (NPs) [2] such as a thin shell, large internal void, and doubled surface area [3] and cation vacancies has raised a lot of interest for their applications in energy storage. Recently Shevchenko et al. [4] reported the role of the high concentration of cation vacancies in hollow iron oxide NPs in lithium intercalation reactions. This report explains significantly higher capacities observed in the case of hollow NPs as compared with their bulk analogues and emphasize the importance of morphology of NPs for targeted applications. Very recently it was found that Mo-substituted γ-Fe2O3 also enhanced lithium ion battery performance by generating additional cation vacancies [1]. These studies motivated us to analyze the structure and morphology of these hollow iron oxide NPs modified by the addition of Mo for lithium ion storage. In this work we report the analysis of samples before and after annealing process and after Li cycling by transmission electron microscopy (TEM), small angle X-ray scattering (SAXS), X-ray absorption fine structure (XAFS) and XPS. SAXS experiments were performed in order to follow changes in morphology and NPs arrange with the Mo addition and after Li intercalation process. XAFS experiments at the Fe K edge and Mo L23 edges were performed in order to understand the origin of the change in Fe vacancies with Mo addition and XPS results were employed to analyze the species at the surface of the NPs. Keywords: iron hollow nanoparticles, lithium ion storage, XAFS, SAXS References: [1] Hahn, B. P., et. al R. Energy Environ. Sci. 2011, 4, 1495.[2] Yin, Y. D., et. al. Science 2004, 304, 711 714. [3] Cabot, A., et. al.Phys. Rev. B 2009, 79, 094419.[4] Koo, B., et. al. Nano Lett. 2012, 12, 24292435. Presenting author’s email: requejo@inifta.unlp.edu.ar