We
report the design and nanoengineering of carbon-film-coated
iron sulfide nanorods (C@Fe7S8) as an advanced
conversion-type lithium-ion storage material. The structural advantages
of the iron-based metal–organic framework (MIL-88-Fe) as both
a sacrificed template and a precursor are explored to prepare carbon-encapsulated
ploy iron sulfide through solid-state chemical sulfurizing. The resulting
core–shell nanorods consisting of approximately 13% carbon
and 87% Fe7S8 have a hierarchically porous structure
and a very high specific surface area of 277 m2 g–1. When tested for use in fabrication of a redox conversion-type lithium-ion
battery, this composite material has demonstrated high lithium-ion
storage capacity at 1148 mA h g–1 under the current
rate of 500 mA g–1 for 170 cycles and an impressive
rate-retention capability at 657 mA h g–1 with a
current density of 2000 mA g–1. On the basis of
systematic structural analysis and microscopic mapping, we discuss
the charge–discharge mechanisms and the crucial factors associated
with the stability and structural changes upon charge–discharge
cycling.
Poly(styrene-b-isobutylene-b-styrene) (PSt−PIB−PSt) triblock copolymers have been prepared for the first time via coupling of living PSt-PIB diblock copolymers in a one-pot procedure. The
PSt−PIB diblock copolymer was synthesized by living sequential cationic polymerization in methylcyclohexane (MeChx)/methyl chloride (MeCl) or hexane (Hex)/MeCl solvent mixtures at −80 °C using TiCl4
as co-initiator. It was found that, due to decomposition of the living PSt ends, the crossover efficiency
(C
eff) from living PSt to IB decreases precipitously with time at close to 100% St conversion. To obtain
high C
eff, IB must therefore be added at ≤95% St conversion. It was also found that in the presence of
unreacted St the rate of IB block copolymerization decreases with time; this was attributed to the formation
of relatively unreactive −St−IB−Cl ends. Due to the relatively high concentration of these ends, coupling
of living PSt−PIB was slow and incomplete. The obtained PSt−PIB−PSt triblock copolymers exhibited
reasonable but significantly lower tensile strength (16−20 MPa) than that (23−25 MPa) reported for
model PSt−PIB−PSt triblock copolymers of similar composition.
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