Understanding Improved Electrochemical Properties in Nickel Fluoride Conversion Electrode Materials by X-ray Absorption Spectroscopy and Pair Distribution Function

摘要

A considerable amount of efforts has been devoted to tailoring their nanostructures to overcome poor electronic conductivity. It has been demonstrated that nanocomposites of carbon and TM fluorides such as FeF2, FeF3, and BiF3 may be utilized as cathodes for high energy lithium ion batteries, revealing a high conversion potential and good cycling properties. In addition, the TM fluoride compounds including M-O covalent bond such as FeOF and Fe2OF4 have been reported that they exhibited better electrochemical properties, since M-O bond provides higher electronic conductivity into highly insulating M-F ionic bond. The mechanisms studies on TM fluorides such as FeF3 and CuF2 have also been intensively conducted using sophisticated techniques such as XAS, PDF and nuclear magnetic resonance (NMR). However there are very few studies on NiF2 based conversion cathode material in terms of the conversion mechanism and electrochemical properties, presumably due to its poor electrochemical properties compared to other metal fluorides.