EELS Valence Mapping in Electron Beam Sensitive FeFx/C Nanocomposites

Conference · Mon Jan 01 04:00:00 EST 2007

OSTI ID:931892

Cosandey, F. ^[1]; Al-Sharab, J. F. ^[1]; Amatucci, Glenn G. ^[1]; Bentley, James ^[2]

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1. Rutgers University
2. ORNL

A new type of positive electrodes for Li-Ion batteries has been synthesized based on FeF{sub 2}/C and FeF3/C nanocomposites with particle size in the 8-12 nm range [1]. The measured high capacities rely on a complete reduction of Fe to its metallic state according to the following reaction: xLi{sup +}+xe{sup -} +Fe{sup x+}Fx = xLiF + Fe{sup 0}, where x=3 and x=2 for FeF3/C and FeF2/C respectively. This electrochemical reaction involves a change in valence state of Fe from 3+ or 2+ to 0 that can be determined uniquely by EELS from the peak energy of the L{sub 3} line and from the L{sub 3}/L{sub 2} line intensity ratio. In this paper, we report EELS mapping results on the electrochemical conversion processes and in particular the mapping of the Fe valence state before and after discharge. This work was performed with a Hitachi HF2000 equipped with a Gatan PEELS and with a FEI CM200 FEG TEM equipped with a Gatan GIF. Both instruments were operated in STEM mode at 200kV with an EELS collection half angle of {beta}=5 mrad and spectrum imaging software.

• Research Organization: Oak Ridge National Laboratory (ORNL); Shared Research Equipment Collaborative Research Center
• Sponsoring Organization: SC USDOE - Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 931892
• Country of Publication: United States
• Language: English

Related Subjects

25 ENERGY STORAGE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
77 NANOSCIENCE AND NANOTECHNOLOGY
CARBON
COMPOSITE MATERIALS
EELS
ELECTROCHEMISTRY
ENERGY-LOSS SPECTROSCOPY
FeF2
IRON FLUORIDES
LITHIUM
METAL-NONMETAL BATTERIES
NANOSTRUCTURES
TEM
VALENCE
Valence Mapping
battery electrode
beam-sensitive material
nanocomposite