Hierarchical Carbon Nanotubes with a Thick Microporous Wall and Inner Channel as Efficient Scaffolds for Lithium–Sulfur Batteries

Abstract

The proposal herein is based on an effi cient sulfur host, namely hierarchical microporous-mesoporous carbonaceous nanotubes (denoted as HMMCNT) that feature a thick microporous wall and inner hollow channel. The electrochemical performance of the composite (HMMCNT-S) is studied systematically at different discharge cut-off voltages and at varying sulfur content. The cycling behavior in different voltage windows is compared and the highest specifi c capacity is shown for HMMCNT-S-50 in the range of 1.4-2.8 V. These results imply that better energy densities can be achieved by controlling the discharge cut-off voltage. Moreover, we show that when the sulfur loading is 50% (HMMCNT-S-50), the cycling and rate performance is better than that of the composite loaded with 40% sulfur (HMMCNT-S-40). Benefi ting from the attractive hierarchical micro/mesoporous confi guration, the obtained hybrid structure not only promotes electron and ion transfer during the charge/discharge process, but also effi ciently impedes polysulfi de dissolution. More specifi cally, the electrode can deliver a specifi c capacity of 558 mA h g −1 even after 150 cycles at a high rate of 1600 mA g −1 with a decay rate of only 0.13% per cycle. Considering the benefi cial structure of these carbon nanotubes, it is very feasible that these structures may also be used in other research fi elds, including in catalysis, as supercapacitors, in drug-delivery applications, for absorption, and so on.

Review of Carbon Materials for Lithium‐Sulfur Batteries

“…Because of its excellent structural properties, carbon nanotubes are also commonly used to coat and modify the separator, and demonstrate excellent electrochemical performance when applied in LSBs. Lately, a functional separator modified with hydroxyl‐functionalized carbon nanotubes (CNTOH) was designed by Ponraj and co‐workers to improve utilization of sulfur element and inhibit intermediate lithium polysulfides, as schematically demonstrated in Figure . Firstly, the hydroxyl groups of CNTOH can provide a strong adsorption of polysulfides and localize lithium polysulfides within sulfur cathode side.…”

Integrated Design of MnO2@Carbon Hollow Nanoboxes to Synergistically Encapsulate Polysulfides for Empowering Lithium Sulfur Batteries

“…Integrated micro/nano, hollow, or yolk shell carbon structures have been designed for the enhancement of the conductivity and entrapment of polysulfides . The commonly used strategic approach is to encapsulate sulfur in conductive, high surface area porous carbon framework (e.g., hierarchical porous carbon, graphene/graphene oxides, 1D carbon nanostructures), polymers derived conductive carbon, and noncarbon porous materials (e.g., metal‐organic framework and mesoporous silica (SBA‐15)) to improve the output of the sulfur cathodes. Despite their great potential in enhancing the performance, the existed carbon/sulfur composites have nonpolar nature and poor affinity toward Li 2 S x ( x = 4–8) both of which inevitably cause the decay of rate capability and even the specific capacity .…”

3D Cube‐Maze‐Like Li‐Rich Layered Cathodes Assembled from 2D Porous Nanosheets for Enhanced Cycle Stability and Rate Capability of Lithium‐Ion Batteries

“…Recently, Li-rich cathode materials (LMNCO), x Li 2 MnO 3 ·(1 − x) LiTMO 2 (0 < x < 1, TM = Mn, Ni, Co, etc. [5][6][7][8][9] On the basis of this, extensive efforts have been devoted to develop nanometersized materials and great progresses have been achieved over the past several years, such as construction of nanoplates, [5] nanowires, [10] nanoparticles, [11] and nanorods, [12] which possess a short Li + diffusion pathway thanks to their diminished dimensions. [3] Nevertheless, the sluggish diffusion of electrons and lithium ions within LMNCO results in electrode polarization and inferior rate capability.…”