Carbon-Nanotube-Encapsulated
FeF<sub>2</sub> Nanorods for High-Performance Lithium-Ion Cathode
Materials
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Abstract
Application
of iron fluoride, a promising candidate of cathode materials for lithium
ion batteries, is being hindered by its poor electrochemical performance
caused by low electronic conductivity and large volume change. Design
of carbon-encapsulated transitional metal compounds (including fluoride,
oxide, sulfide, etc.) structure is one of the most effective strategies
in improving their lithium-ion storage performance. In this work,
we successfully synthesize for the first time carbon-nanotube-encapsulated
FeF<sub>2</sub> nanorods via a facile in situ co-pyrolysis of ferrocene
and NH<sub>4</sub>F. This kind of core/shell carbon nanotube/FeF<sub>2</sub> nanorod exhibits better cyclic stability and rate-performance
used as cathode materials. Better electrochemical performance of the
nanorods should be attributed to the protection of the carbon shell
because, experimentally, it is observed that outer carbon shells suffer
from high internal stress during Li-ion insertion but efficiently
keep the nanorods in the one-dimensional morphology and make nanorods
a good electrical contact with the conductive carbon black. This work
not only prepares high-performance core/shell carbon/iron fluoride
cathode materials, but should also open a facile pathway for design
of various novel nanostructures of other metal fluoride/carbon core/shell
structures for future lithium-ion batteries