Carbon-Metal Fluoride Nanocomposites

The practical electroactivity of electrically insulating iron fluoride was enabled through the use of carbon-metal fluoride nanocomposites (CMFNCs). The nanocomposites were fabricated through the use of high energy mechanical milling and resulted in nanodomains of on the order of 1-20 nm encompassed in a matrix of carbon as characterized by transmission electron microscopy and X-ray diffraction (XRD). Electrochemical characterization of CMFNCs composed of 85/15 wt % resulted in a nanocomposite specific capacity as high as 200 mAh/g (235 mAh/(g of with the electrochemical activity associated with the occurring in the region of 2.8-3.5 V. The CMFNCs revealed encouraging rate capability and cycle life with fade after 50 cycles. Structural evolution during the first lithiation reaction was investigated with the use of ex situ and in situ XRD. Initial results suggest that from 0 to 0.5 in proceeds in a two-phase reaction resulting in a phase with significant redistribution of the Fe atoms within a structure very similar to the base -based CMFNCs also exhibited a very high specific capacity of 600 mAh/g at 70°C due to a reversible reaction at approximately 2 V. © 2003 The Electrochemical Society. All rights reserved.