Synergistically Assembled Li₂S/FWNTs@Reduced Graphene Oxide Nanobundle Forest for Free‐Standing High‐Performance Li₂S Cathodes

Abstract

Lithium sulfide (Li 2 S) has attracted increasing attention as a promising cathode because of its compatibility with more practical lithium-free anode materials and its high specific capacity. However, it is still a challenge to develop Li 2 S cathodes with low electrochemical overpotential, high capacity and reversibility, and good rate performance. This work designs and fabricates a practical Li 2 S cathode composed of Li 2 S/few-walled carbon nano-tubes@reduced graphene oxide nanobundle forest (Li 2 S/FWNTs@rGO NBF). Hierarchical nanostructures are obtained by annealing the Li 2 SO 4 / FWNTs@GO NBF, which is prepared by a facile and scalable solution-based self-assembly method. Systematic characterizations reveal that in this unique NBF nanostructure, FWNTs act as axial shafts to direct the structure, Li 2 S serves as the internal active material, and GO sheets provide an external coating to minimize the direct contact of Li 2 S with the electrolyte. When used as a cathode, the Li 2 S/FWNTs@rGO NBF achieve a high capacity of 868 mAh g −1 Li2S at 0.2C after 300 cycles and an outstanding rate performance of 433 mAh g −1 Li2S even at 10C, suggesting that this Li 2 S cathode is a promising candidate for ultrafast charge/discharge applications. The design and synthetic strategies outlined here can be readily applied to the processing of other novel functional materials to obtain a much wider range of applications.

Poly(4‐styrene sulfonic acid) to Disperse Graphene for Applications in Lithium‐Sulfur Batteries

“…The poor conductivity of S not only decreases the specific capacity and energy density of the fabricated cells, but also results in a high ohmic potential drop (IR drop) that fades the cells very rapidly . A great deal of research into possible solutions to these problems has been carried out . For example, the use of highly conductive graphene‐based materials has been reported to be effective for improving the electrochemical performance of the Li−S battery.…”

Trojan‐Horse‐Like Stimuli‐Responsive Microcapsules

“…Stimuli‐responsive microcapsules that enable on‐demand content release show great power for myriad applications such as drug delivery, self‐healing, and confined microreaction . For developing new‐generation microcarriers, multicompartmental microcapsules, with each compartment protected by a distinct and stable stimuli‐responsive shell for versatile coencapsulation and controlled release, are highly desired.…”

Facile Synthesis of Hierarchical Sulfur Composites for Lithium–Sulfur Batteries

“…However, S also presents a number of challenges that have to be overcome, such as its low electrical conductivity (5 × 10-30 S cm À 1 ), [15] the shuttle effect caused by easy dissolution of the intermediates (high-order polysulfide (PS) species) generated during discharge, [16][17][18][19][20] and the high volume expansion (80 %). [23][24][25][26][27][28][29][30][31][32][33][34] One frequently adopted method is to produce a composite of S and a carbonaceous material. In addition, volume expansion of S can occur during its discharge/lithiation process, which may cause high mechanical stress that damages the cathode.…”

“…[21] The shuttle effect, relating to the dissolution of high-order PS species that are produced as electrochemical intermediates in a polar electrolyte and the followed migration to the lithium anode due to the concentration gradient, results in a continual loss of the active S material from the cathode and thus the eventual decay of the capacity. Carbonaceous materials, including graphene, [23][24][25] graphite, [26] carbon fibers, [27] carbon nanotubes, [28][29][30][31] and carbon nanoparticles, [34] have long been reported to efficiently improve electronic conductivity of S; additionally, the carbon defects were reported to be helpful in inhibiting the PS dissolution and the shuttle effect. [21] The poor electrical conductivity of S, which is also one of pressing issues for the commercialization of LiÀ S batteries, not only results in low capacity and energy density in the batteries, but also causes a high ohmic potential drop that leads to rapid cell fading.…”

“…[23][24][25][26][27][28][29][30][31][32][33][34] One frequently adopted method is to produce a composite of S and a carbonaceous material. Carbonaceous materials, including graphene, [23][24][25] graphite, [26] carbon fibers, [27] carbon nanotubes, [28][29][30][31] and carbon nanoparticles, [34] have long been reported to efficiently improve electronic conductivity of S; additionally, the carbon defects were reported to be helpful in inhibiting the PS dissolution and the shuttle effect. [35,36] In this investigation, a feasible method for easy fabrication of core-shell structured composites of S and carbon nanopowder (nano-CB) is proposed, in which the structural geometry and particle size of the synthesized composites can be adjusted.…”