Despite the fact that lithium-sulfur batteries are regarded as promising next-generation rechargeable battery systems owning to high theoretical specific capacity (1675 mA h g) and energy density (2600 W h kg), several issues such as poor electrical conductivity, sluggish redox kinetics, and severe "shuttle effect" in electrodes still hinder their practical application. MXenes, novel two-dimensional materials with high conductivity, regulable interlayer spacing, and abundant functional groups, are widely applied in energy storage and conversion fields. In this work, a TiC/carbon hybrid with expanded interlayer spacing is synthesized by one-step heat treatment in molten potassium hydroxide. The subsequent experiments indicate that the as-prepared TiC/carbon hybrid can effectively regulate polysulfide redox conversion and has strong chemisorption interaction to polysulfides. Consequently, the TiC/carbon-based sulfur cathode boosts the performance in working lithium-sulfur batteries, in terms of an ultrahigh initial discharge capacity (1668 mA h g at 0.1 C), an excellent rate performance (520 mA h g at 5 C), and an outstanding capacity retention of 530 mA h g after 500 cycles at 1 C with a low capacity fade rate of 0.05% per cycle and stable Coulombic efficiency (nearly 99%). The above results indicate that this composite with high catalytic activity is a potential host material for further high-performance lithium-sulfur batteries.
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http://dx.doi.org/10.1021/acsami.9b23006 | DOI Listing |
Chemistry
December 2024
Dalian University of Technology, No.2 Linggong Road, Ganjingzi District, Dalian, CHINA.
Sulfur-rich copolymers have gained a great deal of attention as promising cathode materials in Li-S batteries due to their low cost and naturally uniform sulfur dispersion. However, the poor electrical conductivity and shuttle effect cause rapid capacity decay and low sulfur utilization especially under high sulfur loading and low electrolyte/sulfur ratio. Herein, the Fe1-xS/C dispersed and Se-containing sulfur-rich polymer (FSP) was synthesized by one-pot reaction of ferrocene, trithioiynuric acid with SexSy.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
December 2024
Henan University, School of Materials Science and Engineering, CHINA.
Sluggish reaction kinetics of sulfur species fundamentally trigger the incomplete conversion of S8↔Li2S and restricted lifespan of lithium-sulfur batteries, especially under high sulfur loading and/or low electrolyte/sulfur (E/S) ratio. Introducing redox mediators (RMs) is an effective strategy to boost the battery reaction kinetics, yet their multifunctionality and shuttle inhibition are still not available. Here, a unique ethyl viologen (EtV²⁺) RM with two highly reversible redox couples (EtV²⁺/EtV⁺, EtV⁺/EtV0) is demonstrated to well match the redox chemistry of sulfur species, in terms of accelerating the electron transfer in S8 reduction, Li2S nucleation and the Li2S oxidation.
View Article and Find Full Text PDFSmall
December 2024
School of Materials science and Engineering, Zhengzhou University, Zhengzhou, 450001, China.
The mesopores and macropores within porous carbon materials help increase the surface for the depostion of solid-state products, reduce the LiS film thickness, enhance electron and mass transport, and accelerate the reaction kinetics. However, an excessive amount of mesopores and macropores can lead to increased electrolyte consumption, particularly at high sulfur loadings, where excessive electrolyte usage hampers the enhancement of practical energy density in lithium-sulfur (Li-S) batteries. A rational pore structure can minimize the amount of electrolyte to fill the pores, thereby reducing electrolyte consumption while achieving rapid reaction kinetics and a high gravimetric energy density.
View Article and Find Full Text PDFSmall
December 2024
School of Physical Science and Technology, Lanzhou University, 222 South Tianshui Road, Lanzhou, 730000, China.
Well-designed structures of the electrocatalyst provide excellent catalytic activity and high structural stability during the sulfur reduction reaction of Lithium-sulfur batteries (LSBs). In this study, a novel and efficient structure is developed to encapsulate bimetallic FeCo nanoalloy catalysts within N-doped carbon nanotube (NCNT) on carbon nanofibers (FeCo@NCNT/CNFs) using a combination of electrospinning and rapid-cooling techniques. The NCNT matrix with abundant sites not only serves as a high pathway for electron transport during the reaction, but its encapsulation structure also acts as armor to protect the FeCo nanoalloy.
View Article and Find Full Text PDFJ Am Chem Soc
December 2024
School of Materials Science and Engineering, Department of Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China.
Sulfurized polyacrylonitrile (SPAN) has emerged as a highly promising cathode material for next-generation lithium-sulfur (Li-S) batteries primarily due to its non-polysulfide dissolution and excellent cycle stability. Nevertheless, the specific roles and impacts of the pyrolyzed polyacrylonitrile, which constitutes the polymer backbone of SPAN, remain inadequately understood. In this study, comprehensive investigations from multiple aspects, including electrochemistry, spectroscopy, electron microscopy, and theoretical calculations, were conducted on a series of SPAN materials with various sulfur contents.
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