Preparation and Characterization of Intermetallic Nanoparticles for Lithium Ion Batteries

Abstract

Nanoparticles based on tin compounds and alloys have been prepared by using the polyol and/or sonochemical methods. Thus, nanoparticulated Fe1-xCoxSn2 solid solutions were prepared by using the polyol method or, alternatively, a combination of the polyol and the sonochemical methods, and the Rietveld refinements of the XRD patterns confirm the formation of the solid solutions solutions. Pure or pyrolyzed polyacrylonitrile (PAN) can be used to create a matrix that encapsulate the metallic particles and improve the electrochemical cycling behavior. Thus, MSn2@PAN (where M=Fe or Co) have been prepared by using dimethylformamide like solvent of PAN and applying high-intensity ultrasonication to achieve small particle size, poor crystallinity and high dispersion. The very small particles of MSn2 exhibit higher tendency to be oxidized in air atmosphere than the larger particles. The very small particle size of the alloy and the organic phase (PAN) contribute to stabilize the interfaces and the contacts in the electrode, as is evidenced by the electrochemical cycling and the impedance spectra. A model is proposed for the electrochemical behavior of the MSn2@PAN electrode materials. MSn2@C materials can be prepared throughout the pyrolysis of the PAN molecules matrix.