Enhanced lithium polysulfide adsorption on an iron-oxide-modified separator for Li-S batteries

Vanadium-Doped Molybdenum Diselenide Accelerates Sulfur Redox Kinetics in Lithium-Sulfur Batteries

The persistent shuttle effect of polysulfides and slow liquid-solid redox kinetics remain major obstacles to the practical application of Lithium-Sulfur (Li─S) batteries. In this study, a vanadium-doped molybdenum diselenide catalyst designed to address these challenges are presented. Experimental analysis and theoretical calculations reveal that V doping slightly disrupts the 2D growth of MoSe2, creating structural defects and abundant edge-active sites. These active sites enhance polysulfide adsorption, facilitate efficient catalytic conversion, and promote the utilization of S species. Additionally, electron redistribution induced by V dopants improves electronic conductivity and accelerates redox kinetics. As a result, Li─S batteries using V0.1Mo0.9Se2 as a catalyst deliver a high discharge capacity of 1467.3 mA h g-1 at 0.1 C and maintain a capacity of 651.9 mA h g-1 after 1000 cycles at 1 C, with an ultralow decay rate of 0.036% per cycle. Under high sulfur loading (5.5 mg cm-2), the batteries exhibit a specific capacity of 803.9 mA h g-1 after 100 cycles and a decay rate of only 0.11% per cycle. This study demonstrates that V doping effectively activates inert MoSe2, providing a promising strategy for designing high-performance sulfur cathode catalysts and advancing the development of next-generation Li─S batteries.

High-entropy oxide hollow spheres as efficient catalysts to accelerate sulfur conversion kinetics toward lithium-sulfur batteries

High-entropy metal oxide ((Fe0.2Co0.2Ni0.2Cu0.2Zn0.2)3O4, HEO) hollow spheres were accurately designed and prepared as efficient catalysts to boost the polysulfide redox kinetics for lithium-sulfur batteries. Owing to the strong chemical adsorption and catalytic effect of HEO on polysulfide transformation, the HEO@S electrode exhibits excellent electrochemical performance.

Amorphous FeSnOx Nanosheets with Hierarchical Vacancies for Room-Temperature Sodium-Sulfur Batteries

Room-temperature sodium-sulfur (RT Na-S) batteries, noted for their low material costs and high energy density, are emerging as a promising alternative to lithium-ion batteries (LIBs) in various applications including power grids and standalone renewable energy systems. These batteries are commonly assembled with glass fiber membranes, which face significant challenges like the dissolution of polysulfides, sluggish sulfur conversion kinetics, and the growth of Na dendrites. Here, we develop an amorphous two-dimensional (2D) iron tin oxide (A-FeSnOx) nanosheet with hierarchical vacancies, including abundant oxygen vacancies (Ovs) and nano-sized perforations, that can be assembled into a multifunctional layer overlaying commercial separators for RT Na-S batteries. The Ovs offer strong adsorption and abundant catalytic sites for polysulfides, while the defect concentration is finely tuned to elucidate the polysulfides conversion mechanisms. The nano-sized perforations aid in regulating Na ions transport, resulting in uniform Na deposition. Moreover, the strategic addition of trace amounts of Ti3C2 (MXene) forms an amorphous/crystalline (A/C) interface that significantly improves the mechanical properties of the separator and suppresses dendrite growth. As a result, the task-specific layer achieves ultra-light (~0.1 mg cm-2), ultra-thin (~200 nm), and ultra-robust (modulus=4.9 GPa) characteristics. Consequently, the RT Na-S battery maintained a high capacity of 610.3 mAh g-1 and an average Coulombic efficiency of 99.9 % after 400 cycles at 0.5 C.

V-Doped CoSe2 Nanowire Catalysts in a 3D-Structured Electrode for Durable Li-S Pouch Cells

Lithium-sulfur (Li-S) batteries have high theoretical energy density and are regarded as a promising candidate for next-generation energy storage systems. However, their practical applications are hindered by the slow kinetics of sulfur conversion and polysulfide shuttling. In particular, large-scale pouch cells show much poor cyclability. Here, we develop a high-efficiency catalyst of V-doped CoSe2 by studying the binary CoSe2-VSe2 system and confirming its effectiveness in accelerating polysulfide conversion. The coin cell tests reveal an initial capacity of 1414 mAh g-1 at 0.1 C and 1049 mAh g-1 at 1 C and demonstrate 1000 times cyclability with a decaying rate of 0.05% per cycle. Furthermore, the assembly and construction of pouch cells were optimized with monolithic three-dimensional (3D) electrodes and a multistacking strategy. Specifically, a 3D metallic scaffold (3MS) was developed to host V-doped CoSe2 nanowires and sulfur. In addition, Janus microspheres of C@TiO2 were synthesized to capture polar polysulfides with their polar part of TiO2 and adsorb nonpolar sulfur with their nonpolar part of carbon. By integrating with 3MS, C@TiO2 microspheres can block all ion channels of 3MS and only allow Li ions in and out. These integral designs and monolithic structures enable multistacking pouch cells with high cyclability. A high-loading pouch cell was demonstrated with a total capacity of 700 mAh. The cell can be cycled for 70 times with a capacity retention of 65.7%. In brief, this work provides an integral strategy of catalyst design and overall 3D assembly for practical Li-S batteries in a large pouch cell format.

SO3-COF@Al2O3 modified cathode electrode materials enhance the cycling ability of lithium sulfur batteries

Herein, a covalent organic framework (SO3-COF) containing sulfonic acid groups has been developed on the surface of alumina by a one-step method, labeled as SO3-COF@Al2O3. The experimental results show that SO3-COF@Al2O3 can effectively inhibit the shuttle effect of soluble lithium polysulfide (LiPSs) in LSBs after loading the active material sulfur, and exhibits better cycling behavior than the initial polymer SO3-COF. The initial discharge specific capacity of this electrode material at 0.05C is as high as 1141 mA h g-1, and the capacity can be maintained at 466 mA h g-1 after 500 cycles with a capacity decay rate of 0.08% per cycle.

Regulating the catalytic behaviour of iron oxyhydroxide by introducing Ni sites for facilitating polysulfide anchoring and conversion

The sluggish conversion kinetics and notorious shuttle effect of polysulfides are critical hindrances to practical implementation of lithium-sulfur batteries. Herein, bimetallic oxyhydroxide (FeNiOOH) as a functional sulfur host is proposed to overcome these obstacles. The introduction of Ni sites can modulate the electronic structure of the active sites to implement strong soluble polysulfide species immobilization and accelerate the conversion reaction kinetics of polysulfides, resulting in improved sulfur utilization and reduced polarization during the electrochemical reaction process. Benefiting from these advantages, FeNiOOH enables the sulfur cathode to deliver superior rate capability and cycling stability.

Porous FeNi Prussian blue cubes derived carbon-based phosphides as superior sulfur hosts for high-performance lithium-sulfur batteries

In contrast to lithium-ion batteries, lithium-sulfur batteries have higher theoretical energy density and lower cost, so they would become competitive in the practical application. However, the shuttle effect of polysulfides and slow oxidation-reduction kinetics can degrade their electrochemical performance and cycle life. In this work, we have first developed the porous FeNi Prussian blue cubes as precursors. The calcination in different atmospheres was employed to make precursors convert into common pyrolysis products or novel carbon-based phosphides, and sulfides, labeled as FeNiP/A-C, FeNiP/A-P, and FeNiP/A-S. When these products serve as host materials in the sulfur cathode, the electrochemical performance of lithium-sulfur batteries is in the order of S@FeNiP/A-P > S@FeNiP/A-S > S@FeNiP/A-C. Specifically, the initial discharge capacity of S@FeNiP/A-P can reach 679.1 mAh g-1at 1 C, and the capacity would maintain 594.6 mAh g-1after 300 cycles. That is because the combination of carbon-based porous structure and numerous well-dispersed Ni2P/Fe2P active sites contribute FeNiP/A-P to obtain larger lithium-ion diffusion, lower resistance, stronger chemisorption, and more excellent catalytic effect than other samples. This work may deliver that metal-organic framework-derived carbon-based phosphides are more suitable to serve as sulfur hosts than carbon-based sulfides or common pyrolysis products for enhancing Li-S batteries' performance.

Ultrathin MgB2 nanosheet-modified polypropylene separator for high-efficiency lithium-sulfur batteries

The separator is an important component in lithium-sulfur (Li-S) batteries. However, the conventional polypropylene (PP) separators have the problem of easy shuttling of lithium polysulfide (LiPSs). Herein, ultrathin magnesium boride (MgB2) nanosheets were prepared by ultrasonic-assisted exfoliation technology, and were suction-filtered onto a separator to serve as a separator modification layer. The introduction of a microporous structure into MgB2 nanosheets after ultrasonic peeling increases the specific surface area and pore volume, with more adsorption sites, which can fully utilize the surface adsorption/catalytic performance of MgB2 for LiPSs and accommodate the volume expansion of lithium sulfide (Li2S). Therefore, MgB2@PP as a separator significantly improves the sulfur utilization and cycle stability in Li-S batteries. When the MgB2@PP separator is used, the reversible specific capacity of the assembled Li-S battery at 0.1 C (current rate) is 1184 mAh/g, and the specific capacity at 2 C is 732 mAh/g. After 500 cycles at 2 C, it remains at 497 mAh/g.

Core-shell oxygen-deficient Fe2O3 polyhedron serves as an efficient host for sulfur cathode

Herein, an oxygen-defect-rich core-shell Fe2O3-x@C polyhedral sulfur host was prepared, which effectively promoted electrochemical conversion and further inhibited the "shuttle effect" in lithium-sulfur (Li-S) batteries. Fe2O3-x@C@S provided a high initial capacity of 1395 mA h g-1 and a low attenuation of ∼0.067% per cycle.