Novel Sulfur Host Composed of Cobalt and Porous Graphitic Carbon Derived from MOFs for the High-Performance Li–S Battery

Abstract

A composite consisting of cobalt and graphitic porous carbon (Co@GC-PC) is synthesized from bimetallic metal-organic frameworks and employed as the sulfur host for high-performance Li-S batteries. Because of the presence of a large surface area (724 m g) and an abundance of macro-/mesopores, the Co@GC-PC electrode is able to alleviate the debilitating effect originating from the volume expansion/contraction of sulfur species during the cycling process. Our in situ UV/vis analysis indicates that the existence of Co@GC-PC promotes the adsorption of polysulfides during the discharge process. Density functional theory calculations show a strong interaction between Co and LiS and a low decomposition barrier of LiS on Co(111), which is beneficial to the following LiS oxidation in the charge process. As a result, at 0.2C, the discharge capacity of the S/Co@GC-PC cathode is stabilized at 790 mAh g after 220 cycles, much higher than that of a carbon-based cathode, which delivers a discharge capacity of 188 mAh g.

Insight into the Anchoring and Catalytic Effects of VO2 and VS2 Nanosheets as Sulfur Cathode Hosts for Li–S Batteries

“…Here, the adsorption conformations of S 8 Figure S2 in the Supporting Information). The anchoring abilities of VO 2 and VS 2 were investigated by performing adsorption experimentsb yd osing the same amount (5.0 mg) of VO 2 and VS 2 into a2mmol L À1 Li 2 S 6 solution (Figure 3i).…”

“…In addition, high‐order lithium polysulfides (LiPSs, Li 2 S n , n =4, 6, or 8) formed during discharge are soluble in aprotic electrolytes. A portion of LiPSs shuttle to the Li‐metal anode and deposit there, resulting in rapid capacity decay …”

“…Ap ortion of LiPSs shuttle to the Li-metal anode and deposit there,r esulting in rapid capacity decay. [5,[7][8][9][10][11] Various strategies have been explored to address the aforementioned issues, including the use of Sh ost materials (HMs), [6,[12][13][14][15][16] coated separators, [17,18] interlayers, [19] and electrolyte additives. [20,21] To improvet he electronic conductivity of S electrodes, various carbon-based HMs, such as graphene, [22,23] mesoporousc arbon, [24,25] carbon nanotubes, [26,27] and carbon nanospheres, [28] have been intensively examined.…”

Facile Synthesis of Hierarchical Sulfur Composites for Lithium–Sulfur Batteries

“…To achieve energy requirements, the development of new electrode materials with higher capacity is a prerequisite. 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 %). [8] Among the many active cathode materials, elemental sulfur (S) is a highly promising candidate due to its extremely high theoretical capacity of 1672 mAh g À 1 , which is more than ten times greater than that of most commercial cathode materials.…”

“…[9][10][11][12][13][14] In addition to its high specific capacity, S presents other attractive advantages, including its low cost, nontoxicity, and great abundance in the earth's crust. 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 %). [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.…”