Pomegranate‐Structured Silica/Sulfur Composite Cathodes for High‐Performance Lithium–Sulfur Batteries

Abstract

Porous materials have many structural advantages for energy storage and conversion devices such as rechargeable batteries, supercapacitors, and fuel cells. When applied as a host material in lithium-sulfur batteries, porous silica materials with a pomegranate-like architecture can not only act as a buffer matrix for accommodating a large volume change of sulfur, but also suppress the polysulfide shuttle effect. The porous silica/sulfur composite cathodes exhibit excellent electrochemical performances including a high specific capacity of 1450 mA h g , a reversible capacity of 82.9 % after 100 cycles at a rate of C/2 (1 C=1672 mA g ) and an extended cyclability over 300 cycles at 1 C-rate. Furthermore, the high polysulfide adsorption property of porous silica has been proven by ex-situ analyses, showing a relationship between the surface area of silica and polysulfide adsorption ability. In particular, the modified porous silica/sulfur composite cathode, which is treated by a deep-lithiation process in the first discharge step, exhibits a highly reversible capacity of 94.5 % at 1C-rate after 300 cycles owing to a formation of lithiated-silica frames and stable solid-electrolyte-interphase layers.

Semihollow Core–Shell Nanoparticles with Porous SiO2 Shells Encapsulating Elemental Sulfur for Lithium–Sulfur Batteries

“…To address these limitations, nanostructured materials have been designed as sulfur hosts for Li – S batteries. − While most-studied porous carbon-based hosts improve sulfur conversion by facilitating electron transport, nonpolar carbon is a nonideal host for absorbing polar polysulfides due to weak interactions. ,, To strengthen the host – polysulfide interactions, inorganic oxide materials such as TiO 2 , , Al 2 O 3 , , and SiO 2 , have also been used as traps for polysulfides via chemisorption and/or physisorption. Among them, SiO 2 -based sulfur hosts are of special interest due to their low cost, chemical stability, and ease of synthesis using wet chemistry .…”

“…By constructing core–shell nanoparticles with porous SiO 2 shells and sulfur cores (i.e., S@SiO 2 ), ,− the shuttling of polysulfides can be suppressed inside the shell, and the volume expansion during lithiation can be accommodated. However, due to the nonconductive nature of SiO 2 , the rate performance of these cathodes is typically unsatisfactory. ,, …”

“…However, due to the nonconductive nature of SiO 2 , the rate performance of these cathodes is typically unsatisfactory. 21,22,39 Herein, we describe a strategy for preparing silica-coated sulfur core−shell nanoparticles that involve the conversion of initial silica-coated zinc sulfide nanoparticles to sulfur cores with a concomitant decrease in volume (see Scheme 1). This latter feature is critical to improve cycle performance due to the large volume expansion of the sulfur core upon lithiation.…”

Synergetic Effects of Multifunctional Composites with More Efficient Polysulfide Immobilization and Ultrahigh Sulfur Content in Lithium–Sulfur Batteries

“…This method can hinder the dissolution and diffusion of LiPSs to some degree; Chen et al investigated different surfactants decorated with porous carbon as the sulfur host and concluded that the sodium dodecyl sulfonate-anchored composite material revealed the strongest interactions between LiPSs and the oxygen-containing functional groups in the surfactants . Another efficient method is to use metal oxides with well-defined nanostructures, such as SiO 2 , TiO 2 , MnO 2 , and V 2 O 5 . − Recently, Nazar et al studied Ti 4 O 7 as the host for LSBs and found that it exhibited good affinity for LiPSs and excellent cycle stability because of its metallic conductivity and strong chemical binding ability with LiPSs . Magnéli phase titanium oxides (e.g., Ti 4 O 7 ) have a unique crystal and electron structure, which can provide a good conductivity close to the conductivity of metal.…”