Structure and Electrochemistry of Novel Silver Metal Oxyfluoride Perovskite: Cathode Materials for High Volumetric Energ
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Structure and Electrochemistry of Novel Silver Metal Oxyfluoride Perovskite: Cathode Materials for High Volumetric Energy Storage W. Tong1, W-S. Yoon2 and G. G. Amatucci1 1 Energy Storage Research Group, Department of Materials Science and Engineering, Rutgers, The State University of New Jersey, North Brunswick, NJ, 08902, U.S.A. 2 Brookhaven National Laboratory, Upton, New York, 11973, U.S.A. ABSTRACT A novel electroactive nanostructured silver molybdenum oxyfluoride (SMOF) perovskite was successfully synthesized via mechanochemistry through the use of AgFx and MoO3. The structure of the SMOF perovskite has been examined utilizing X-ray powder diffraction (XRD) combined with X-ray absorption spectroscopy (XAS) and elemental analysis. The SMOF perovskite exhibited a very good electrochemical activity. A detailed in-situ electrochemical study by XRD and XAS was carried out. Finally, preliminary work on fabrication of a metallic Ag2F phase and optimization of the rate capability of SMOF perovskite is presented. INTRODUCTION Cathode materials exhibiting a very high volumetric energy density and a good power need to be developed for an ever increasing demand of portable electronic devices in many fields including biomedical. Relative to other applications, material cost has a low priority in biomedical relative to its performance (high energy density, voltage > 3 V). Presently, these needs are being met by silver vanadium oxides (SVO), Li/CF1 and the Li-I2 for a different rate application1. Other than these, metal fluorides are electrochemically attractive due to their high theoretical output voltage and high energy density. Recently, a new avenue has been presented through the fabrication of carbon metal fluoride nanocomposites (CMFNCS) or mixed conducting matrices (MCM), which successfully enabled the attractive electrochemical activity of these fluorides (BiF32, FeF33 and CuF24). Surpassing CuF2 and BiF3, AgF and AgF2 are of interest due to their theoretical higher output voltages (4.16 V and 4.46 V) and energy densities (6.21 Wh/cc and 9.1 Wh/cc). In contrast to the aforementioned nanocomposite, we found the formation of a new nanocompound, silver molybdenum oxyfluoride, by high-energy milling (HEM) AgFx and MoO3. This new compound exhibited a very good conductivity and successfully enabled the electrochemical activity of the unstable and insulating silver fluoride without the presence of the conductive carbon matrix5. In this paper, we present our current work on the structure and electrochemistry of SMOF perovskite in details. In addition, preliminary work on the fabrication of metallic Ag2F phase and optimization of the rate capability of SMOF perovskite is also discussed. EXPERIMENT Commercially available AgF2 (Aldrich, 98+%) or AgF (Aldrich, 99%) and MoO3 (Alfa Aesar, 99.95%) were utilized as precursors to synthesize SMOF perovskite.1g pre-mixed
stoichiometric powders were sealed in a He-filled glove box (dew point = -80 ˚C) and highenergy milled for 45 min in an Spex 8000 Certiprep mixer/mill.
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