Discrete Hollow Carbon Spheres Derived from Pyrolytic Copolymer Microspheres for Li-S Batteries

Abstract

Discrete hollow carbon spheres (HCSs) with a high surface-to-volume ratio and distinct conducting shell have attracted immense attention as electrode materials for batteries and supercapacitors. In this study, we developed a novel and scalable method to synthesize well-defined HCSs. The HCSs were prepared using a pyrolytic soft template of styrene/acrylic acid copolymer microspheres. Sulfur could be effectively confined inside the pores of the uniform-sized HCSs (average diameter = 320 nm, shell thickness = 40-50 nm) to produce a S/HCS-65-IM (S content = 65 wt%) Li-S cathode using a modified sulfur-loading method involving solution impregnation followed by melt-diffusion (IM). S/HCS-65-IM delivered much higher capacity and greater cycling stability over 200 cycles and showed much lower impedance build up than S/HCS-65-PM prepared via the conventional melt-diffusion of a physical mixture of sulfur powder and HCSs. The sulfur utilization of S/HCS-65-IM was further improved by more than 20% by suppressing its lithium-polysulfide shuttle effect using a carbon-coated separator (CCS). The S/HCS-65-IM cathode (with CCS) also exhibited excellent cycling stability (capacity retention of >81% after 200 cycles at 0.5 C) and high rate capability with a reduced interfacial charge transfer resistance, suggesting that S/HCS-65-IM (with CCS) is a promising cathode for Li-S batteries.

Ultrathin MoS2 Nanosheets Encapsulated in Hollow Carbon Spheres: A Case of a Dielectric Absorber with Optimized Impedance for Efficient Microwave Absorption

“…The plot of the Barrett–Joyner–Halenda pore size distribution curve obtained using the adsorption branch reveals a pore size of ∼1.9 nm. It is well known that micropores could provide favorable pathways for the ion penetration in HCSs. , Therefore, when the uniform HCSs was used as a template during the hydrothermal treatment process, the high penetration of Mo and S precursors around HCSs allows the nucleation of MoS 2 , resulting in ultrathin MoS 2 nanosheets encapsulated in HCSs. Figure e displays the SEM morphologies of MoS 2 @HCS.…”

Simplifying the synthesis of carbon inverse opals

“…C-H band signatures have previously been observed in the FTIR spectra of carbon nanostructures prepared via hydrothermal treatment. [43][44][45][46] The weak band at 1695 cm À1 is assigned to C]C stretching and the band observed at 1575 cm À1 may be attributed to either C]N or C]C stretching vibrations. 47,48 The FTIR spectra indicate that there are residual functional groups present on the surface of all carbon samples studied.…”

Structure Design and Composition Engineering of Carbon‐Based Nanomaterials for Lithium Energy Storage

“…By contrast, soft‐templating presents a simple and facile procedure . Organic surfactants, block copolymers and emulsion droplets are usually adopted as SDAs for direct generation of hollow structures via a self‐assembly process.…”