Iron-based
sulfides have been deemed as an appealing anode material
for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) for
their high theoretical capacity and low cost. However, their practical
application is limited by drastic volume expansion during cycling
and low-intrinsic electronic conductivity. In this work, we report
a FeS2/Fe7S8-rGO composite synthesized
via a facile solvothermal method as an LIB/SIB anode. The FeS2/Fe7S8-rGO anode exhibits an excellent
Li-storage capacity of 514 mAh g–1 at 2.0 A g–1 after 3000 cycles and a Na-storage capacity of 650
mAh g–1 at 0.2 A g–1 after 250
cycles, respectively. The rGO matrix is deemed responsible for providing
good electron conduction and alleviating volume expansion during cycling.
The electrokinetic analysis confirms a large portion of intercalational
pseudocapacitance as a major contribution to the superior rate performance.
In situ X-ray diffraction further reveals details of a combined intercalational
and conversional Li-ion storage mechanisms in this Fe-sulfide-based
anode. Finally, density functional theory calculations suggest that
there exists a synergistic effect at the heterointerface between FeS2 and Fe7S8 to promote electrokinetics.
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