2 research outputs found
Effective Trapping of Lithium Polysulfides Using a Functionalized Carbon Nanotube-Coated Separator for Lithium–Sulfur Cells with Enhanced Cycling Stability
The
critical issues that hinder the practical applications of lithium–sulfur
batteries, such as dissolution and migration of lithium polysulfides,
poor electronic conductivity of sulfur and its discharge products,
and low loading of sulfur, have been addressed by designing a functional
separator modified using hydroxyl-functionalized carbon nanotubes
(CNTOH). Density functional theory calculations and experimental results
demonstrate that the hydroxyl groups in the CNTOH provoked strong
interaction with lithium polysulfides and resulted in effective trapping
of lithium polysulfides within the sulfur cathode side. The reduction
in migration of lithium polysulfides to the lithium anode resulted
in enhanced stability of the lithium electrode. The conductive nature
of CNTOH also aided to efficiently reutilize the adsorbed reaction
intermediates for subsequent cycling. As a result, the lithium–sulfur
cell assembled with a functional separator exhibited a high initial
discharge capacity of 1056 mAh g<sup>–1</sup> (corresponding
to an areal capacity of 3.2 mAh cm<sup>–2</sup>) with a capacity
fading rate of 0.11% per cycle over 400 cycles at 0.5 C rate
Gold-Decorated Block Copolymer Microspheres with Controlled Surface Nanostructures
Gold-decorated block copolymer microspheres (BCP-microspheres) displaying various surface morphologies were prepared by the infiltration of Au precursors into polystyrene-<i>b</i>-poly(4-vinylpyridine) (PS-<i>b</i>-P4VP) microspheres. The microspheres were fabricated by emulsifying the PS-<i>b</i>-P4VP polymers in chloroform into a surfactant solution in water, followed by the evaporation of chloroform. The selective swelling of the P4VP domains in the microspheres by the Au precursor under acidic conditions resulted in the formation of Au-decorated BCP-microspheres with various surface nanostructures. As evidenced by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) measurements, dotted surface patterns were formed when microspheres smaller than 800 nm were synthesized, whereas fingerprint-like surface patterns were observed with microspheres larger than 800 nm. Au nanoparticles (NPs) were located inside P4VP domains near the surfaces of the prepared microspheres, as confirmed by TEM. The optical properties of the BCP-microspheres were characterized using UV–vis absorption spectroscopy and fluorescence lifetime measurements. A maximum absorption peak was observed at approximately 580 nm, indicating that Au NPs are densely packed into P4VP domains on the microspheres. Our approach for creating Au-NP-hybrid BCP-microspheres can be extended to other NP systems such as iron-oxide or platinum NPs. These precursors can also be selectively incorporated into P4VP domains and induce the formation of hybrid BCP-microspheres with controlled surface nanostructures