A High Conductivity 1D π–d Conjugated Metal–Organic Framework with Efficient Polysulfide Trapping‐Diffusion‐Catalysis in Lithium–Sulfur Batteries

Abstract

The shuttling behavior and sluggish conversion kinetics of the intermediate lithium polysulfides (LiPS) represent the main obstructions to the practical application of lithium–sulfur batteries (LSBs). Herein, a 1D π–d conjugated metal–organic framework (MOF), Ni‐MOF‐1D, is presented as an efficient sulfur host to overcome these limitations. Experimental results and density functional theory calculations demonstrate that Ni‐MOF‐1D is characterized by a remarkable binding strength for trapping soluble LiPS species. Ni‐MOF‐1D also acts as an effective catalyst for S reduction during the discharge process and Li2S oxidation during the charging process. In addition, the delocalization of electrons in the π–d system of Ni‐MOF‐1D provides a superior electrical conductivity to improve electron transfer. Thus, cathodes based on Ni‐MOF‐1D enable LSBs with excellent performance, for example, impressive cycling stability with over 82% capacity retention over 1000 cycles at 3 C, superior rate performance of 575 mAh g−1 at 8 C, and a high areal capacity of 6.63 mAh cm−2 under raised sulfur loading of 6.7 mg cm−2. The strategies and advantages here demonstrated can be extended to a broader range of π–d conjugated MOFs materials, which the authors believe have a high potential as sulfur hosts in LSBs.

Thiol-Containing Metal–Organic Framework-Decorated Carbon Cloth as an Integrated Interlayer–Current Collector for Enhanced Li–S Batteries

“…The high-resolution Li 1s spectrum of pristine Li 2 S 6 in Figure b shows a single peak at 55.8 eV, which is assigned to the Li–S bond. After the adsorption test, the peak downshifted to 54.2 eV, indicating the formation of a Li bond between Li in the polysulfide and S from the thiol group, which agrees well with previous studies. , It is worth noting that the thiol groups exist as thiyl radicals (S • ) and thiolates (S – ) in Li–S batteries. ,, Figure c shows the S 2p spectra of UiO-66­(SH) 2 and UiO-66 particles after the interaction with Li 2 S 6 . In the case of UiO-66­(SH) 2 , the S 2p spectrum comprises two pairs of peaks at 164 and 161 eV, classified as the S–Li + bond (S –1 ) and the S–S bond (S 0 ) .…”

“…After the adsorption test, the peak downshifted to 54.2 eV, indicating the formation of a Li bond between Li in the polysulfide and S from the thiol group, which agrees well with previous studies. 57,58 It is worth noting that the thiol groups exist as thiyl radicals (S • ) and thiolates (S − ) in Li−S batteries. 57,59,60 Figure 5c shows the S 2p spectra of UiO-66(SH) 2 and UiO-66 particles after the interaction with Li 2 S 6 .…”

Enhanced Polysulfide Conversion with Highly Conductive and Electrocatalytic Iodine‐Doped Bismuth Selenide Nanosheets in Lithium–Sulfur Batteries

“…[1][2][3][4][5] However, their practical use is still hindered by the electrically insulating nature of sulfur and its discharge products (Li 2 S/ Li 2 S 2 ), [6][7][8] a low utilization of the active material, and a moderate cycling stability associated with the large volume expansion of the cathode upon lithiation [9][10][11][12] and the shuttle of the soluble intermediate lithium polysulfides (LiPS). [13][14][15] These…”

Atomically distributed asymmetrical five-coordinated Co–N5 moieties on N-rich doped C enabling enhanced redox kinetics for advanced Li–S batteries

“…The reduction peaks of a and d can be described to the chemical conversions of Li 2 S 6 to Li 2 S and S 8 to Li 2 S 6 on the working electrode, respectively. 3,8,34 Similarly, the other two oxidation peaks of b and c belong to the oxidation processes of Li 2 S to Li 2 S 6 and Li 2 S 6 to S 8 , respectively. Specifically, the obvious redox peaks for CoN5 SA/NC verify the superior electrocatalytic performance in the redox conversion of LiPSs compared with the reference samples.…”

“…The potential peaks represent the overpotentials for the solid–liquid conversion of insoluble Li 2 S to soluble LiPSs. 8,34 CoN5 SA/NC as a composite separator displayed the lowest overpotential in the charge profiles among those of the catalysts as the composite separators, indicating fastest reaction kinetics for the solid–liquid conversion. Similarly, the negative potential peak of the second discharge plateaus for discharge curves (Fig.…”