Ni Single Atoms on MoS2 Nanosheets Enabling Enhanced Kinetics of Li-S Batteries

The practical application of Li-S batteries is seriously hindered due to its shuttle effect and sluggish redox reaction, which requires a better functional separator to solve the problems. Herein, polypropylene separators modified by MoS₂ nanosheets with atomically dispersed nickel (Ni-MoS₂) are prepared to prevent the shuttle effect and facilitate the redox kinetics for Li-S batteries. Compared with pristine MoS₂ nanosheets, Ni-MoS₂ nanosheets exhibit both excellent adsorption and catalysis performance for overcoming the shuttle effect. Assembled with this novel separator, the Li-S batteries exhibit an admirable cycling stability at 2 C over 400 cycles with 0.01% per cycle decaying. In addition, even with a high sulfur loading of 7.5 mg cm⁻², the battery still provides an initial capacity of 6.9 mAh cm⁻² and remains 5.9 mAh cm⁻² after 50 cycles because of the fast convention of polysulfides catalyzed by Ni-MoS₂ nanosheets, which is further confirmed by the density functional theory (DFT) calculations. Therefore, the proposed strategy is expected to offer a new thought for single atom catalyst applying in Li-S batteries.     

Modulating d-Band Electronic Structures of Molybdenum Disulfide via p/n Doping to Boost Polysulfide Conversion in Lithium-Sulfur Batteries

Polysulfide shuttle effect and sluggish sulfur reaction kinetics severely impede the cycling stability and sulfur utilization of lithium-sulfur (Li-S) batteries. Modulating d-band electronic structures of molybdenum disulfide electrocatalysts via p/n doping is promising to boost polysulfide conversion and suppress polysulfide migration in lithium-sulfur batteries. Herein, p-type V-doped MoS₂ (V-MoS₂) and n-type Mn-doped MoS₂ (Mn-MoS₂) catalysts are well-designed. Experimental results and theoretical analyses reveal that both of them significantly increase the binding energy of polysulfides on the catalysts’ surface and accelerate the sluggish conversion kinetics of sulfur species. Particularly, the p-type V-MoS₂ catalyst exhibits a more obvious bidirectional catalytic effect. Electronic structure analysis further demonstrates that the superior anchoring and electrocatalytic activities are originated from the upward shift of the d-band center and the optimized electronic structure induced by duplex metal coupling. As a result, the Li-S batteries with V-MoS₂ modified separator exhibit a high initial capacity of 1607.2 mAh g⁻¹ at 0.2 C and excellent rate and cycling performance. Moreover, even at a high sulfur loading of 6.84 mg cm⁻², a favorable initial areal capacity of 8.98 mAh cm⁻² is achieved at 0.1 C. This work may bring widespread attention to atomic engineering in catalyst design for high-performance Li-S batteries.     

MoS2/Celgard Separator as Efficient Polysulfide Barrier for Long‐Life Lithium–Sulfur Batteries

A high lithium conductive MoS₂/Celgard composite separator is reported as efficient polysulfides barrier in Li–S batteries. Significantly, thanks to the high density of lithium ions on MoS₂ surface, this composite separator shows high lithium conductivity, fast lithium diffusion, and facile lithium transference. When used in Li–S batteries, the separator is proven to be highly efficient for depressing polysulfides shuttle, leading to high and long cycle stability. With 65% of sulfur loading, the device with MoS₂/Celgard separator delivers an initial capacity of 808 mAh g^?1 and a substantial capacity of 401 mAh g^?1 after 600 cycles, corresponding to only 0.083% of capacity decay per cycle that is comparable to the best reported result so far. In addition, the Coulombic efficiency remains more than 99.5% during all 600 cycles, disclosing an efficient ionic sieve preventing polysulfides migration to the anode while having negligible influence on Li⁺ ions transfer across the separator. The strategy demonstrated in this work will open the door toward developing efficient separators with flexible 2D materials beyond graphene for energy‐storage devices.     

Amorphous Fe-Phytate Enables Fast Polysulfide Redox for High-Loading Lithium Sulfur Batteries

Utilizing catalysts to accelerate polysulfides conversion are of paramount importance to eliminate the shuttling effect and improve the practical performance of lithium-sulfur (Li-S) batteries. The amorphism, attributes to the abundant unsaturated surface active sites, has recently been recognized as a contribution to increase the activity of catalysts. However, the investigation on amorphous catalysts has received limited interest in lithium-sulfur batteries due to lack of understanding of their composition structure activity. Herein, a amorphous Fe-Phytate structure is proposed to enhance polysulfide conversion and suppress polysulfide shuttling by modifying polypropylene separator (C-Fe-Phytate@PP). The polar Fe-Phytate with distorted VI coordination Fe active centers strongly intake polysulfide electron by forming Fe S bond to accelerate the polysulfide conversion. The surface mediated polysulfides redox gives rise to a higher exchange current in comparison with carbon. Furthermore, Fe-Phytate owns robust adsorption to polysulfide and effectively reduce the shuttling effect. With the C-Fe-Phytate@PP separator, the Li-S batteries exhibit an outstanding rate capability of 690 mAh g⁻¹ at 5 C and an ultrahigh areal capacity of 7.8 mAh cm⁻² even at a high sulfur loading of 7.3 mg cm⁻². The work provides a novel separator for facilitating the actual applications of Li-S batteries.     

Dual-Defect Engineering of Bidirectional Catalyst for High-Performing Lithium-Sulfur Batteries

Practical applications of lithium-sulfur (Li-S) batteries have been hindered by sluggish reaction kinetics and severe capacity decay during charge-discharge cycling due to the notorious shuttle effect of polysulfide and the unfavored deposition and dissolution of Li₂S. Herein, to address these issues, a double-defect engineering strategy is developed for preparing Co-doped FeP catalyst containing P vacancies on MXene, which effectively improves the bidirectional redox of Li₂S. Mechanism analysis indicates that P vacancy accelerates Li₂S nucleation via increased unsaturated sites, and Co doping generates local electric field to reduce the reaction energy barrier and accelerate Li₂S dissolution. MXene provides highly conductive channels for electron transport, and effectively captures polysulfide. The double-defect catalyst enables an impressive reversible specific capacity of 1297.9 mAh g⁻¹ at 0.2 C, and excellent rate capability of 726.5 mAh g⁻¹ at 4 C. Remarkably, it demonstrates excellent cycling stability with capacity retention of 533.3 mAh g⁻¹ after 500 cycles at 2 C. The results can unlock the double-defect engineering of vacancy induction and heteroatomic doping towards practical Li-S batteries.     

Functional CNTs@EMIM+-Br− Electrode Enabling Polysulfides Confining and Deposition Regulating for Solid-State Li-Sulfur Battery

With an extremely high theoretical energy density, poly(ethylene oxide) (PEO)-based solid-state lithium-sulfur (Li-S) batteries are emerging as one of the most feasible and safest battery storage systems. However, the long-term cycling performance is severely impeded by polysulfides (Li₂S_n, n = 4–8) shuttling and terrible electrode passivation from the electronic insulating Li₂S. Here, a novel cathode through chemically grafted 1-Ethyl-3-methylimidazolium bromide (EMIM⁺-Br⁻) to carbon nanotube (CNTs) for PEO-based Li-S batteries is reported (CNTs@EMIM-Br/S). Concretely, bi-functional mediator EMIM⁺-Br⁻ not only inhibits the polysulfides shuttling by strong chemical interactions via EMIM⁺, but also facilitates the electrochemical kinetics for promoting the formation of 3D particulate Li₂S through high donor anion (Br⁻). Satisfactorily, dual-function CNTs@EMIM-Br/S cathode exhibits high sulfur utilization with the capacity of up to 1298 mAh g⁻¹, and keeps high capacity retention of 80.2% at 0.2 C after 350 cycles, exceeding that of many reported PEO-based solid-state Li-S batteries. This work will open a new door for rationally designed architecture to enable the practical applications of advanced Li-S batteries.     

Synergistically Designed Dual Interfaces to Enhance the Electrochemical Performance of MoO2/MoS2 in Na- and Li-Ion Batteries

It is indispensable to develop and design high capacity, high rate performance, long cycling life, and low-cost electrodes materials for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Herein, MoO₂/MoS₂/C, with dual heterogeneous interfaces, is designed to induce a built-in electric field, which has been proved by experiments and theoretical calculation can accelerate electrochemical reaction kinetics and generate interfacial interactions to strengthen structural stability. The carbon foam serves as a conductive frame to assist the movement of electrons/ions, as well as forms heterogeneous interfaces with MoO₂/MoS₂ through C S and C O bonds, maintaining structural integrity and enhancing electronic transport. Thanks to these unique characteristics, the MoO₂/MoS₂/C renders a significantly enhanced electrochemical performance (324 mAh g⁻¹ at 1 A g⁻¹ after 1000 cycles for SIB and 500 mAh g⁻¹ at 1 A g⁻¹ after 500 cycles for LIBs). The current work presents a simple, useful and cost-effective route to design high-quality electrodes via interfacial engineering.     

Insight into Accelerating Polysulfides Redox Kinetics by BN@MXene Heterostructure for Li–S Batteries

Sluggish redox kinetics and shuttle effect of polysulfides hinder the extensive application of the lithium–sulfur batteries (LSBs). Herein a functional heterostructure of boron nitride (BN) and MXene with an alternately layered structure (BN@MXene) is designed as separator interlayer. High efficiency Li⁺ transmission, uniform lithium deposition, strong adsorption, and efficient catalytic conversion activities of lithium polysulfides (LiPSs) realized by this heterostructure are confirmed by experiments and theoretical calculations. The alternately layered structure provides unblocked ion transmission channels and abundant active sites to accelerate the polysulfides redox kinetics with reduced energy barriers of oxidation and reduction reactions. As a result, the LSBs deliver an initial discharge capacity of up to 1273.9 mAh g⁻¹ at 0.2 °C and a low decay of 0.058% per cycle in long-term cycling up to 700 cycles at 1 °C. This work provides an effective designing strategy to accelerate the polysulfides redox kinetics for advanced Li–S electrochemical system.     

Defect-Rich Single Atom Catalyst Enhanced Polysulfide Conversion Kinetics to Upgrade Performance of Li–S Batteries

Lithium–sulfur (Li–S) batteries have attracted considerable attention owing to their extremely high energy densities. However, the application of Li–S batteries has been limited by low sulfur utilization, poor cycle stability, and low rate capability. Accelerating the rapid transformation of polysulfides is an effective approach for addressing these obstacles. In this study, a defect-rich single-atom catalytic material (Fe-N4/DCS) is designed. The abundantly defective environment is favorable for the uniform dispersion and stable existence of single-atom Fe, which not only improves the utilization of single-atom Fe but also efficiently adsorbs polysulfides and catalyzes the rapid transformation of polysulfides. To fully exploit the catalytic activity, catalytic materials are used to modify the routine separator (Fe-N₄/DCS/PP). Density functional theory and in situ Raman spectroscopy are used to demonstrate that Fe-N₄/DCS can effectively inhibit the shuttling of polysulfides and accelerate the redox reaction. Consequently, the Li–S battery with the modified separator achieves an ultralong cycle life (a capacity decay rate of only 0.03% per cycle at a current of 2 C after 800 cycles), and an excellent rate capability (894 mAh g⁻¹ at 3 C). Even at a high sulfur loading of 5.51 mg cm⁻² at 0.2 C, the reversible areal capacity still reaches 5.4 mAh cm⁻².     

S,N-codoped carbon capsules with microsized entrance: Highly stable S reservoir for Li-S batteries

Nanostructured carbon materials are extensively applied as host materials to improve the utilization rate and reversibility of elemental sulfur in lithium sulfur (Li-S) batteries. Here, S, N-codoped carbon capsules (SNCCs) with microporous walls, prepared by a self-assembly process, are used as the sulfur host material in Li-S batteries. The SNCCs provide plenty of micron-sized cavities to accommodate a high S loading, which are sealed by thick walls with microsized entrance to efficently suppress the shuttle effect of lithium polysulfides. As the cathode in Li-S battery, the SNCCs/sulfur composite with a sulfur mass loading of 70 wt% exhibits a high average reversible capacity of 1220 and 1116 mA h g^?1 at 0.5C and 1C, respectively, superior rate performance (905 and 605 mAh g^?1 at 5C and 10C, respectively) and excellent cycling stability (capacity fading rate of 0.03% per cycle in 500 cycles). Even at a high sulfur areal loading of 7.3 mg/cm², the SNCCs/0.7S electrode still deliver a high initial discharge capacity of 838 mAh g^?1 and keeps at 730 mAh g^?1 after 100 cycles, corresponding to an extraordinary capacity retention of 87.1%, showing an excellent cyclic stability. The outstanding electrochemical performance is associated with the unique capsule structure with abundant volume, microsized entrance and high conductivity. Our results provides a new strategy to prepare highly stable sulfur-carbon composites for the application in Li-S batteries.     

Medium-Entropy-Alloy FeCoNi Enables Lithium–Sulfur Batteries with Superb Low-Temperature Performance

Lithium-sulfur battery suffers from sluggish kinetics at low temperatures, resulting in serious polarization and reduced capacity. Here, this work introduces medium-entropy-alloy FeCoNi as catalysts and carbon nanofibers (CNFs) as hosts. FeCoNi nanoparticles are in suit synthesized in cotton-derived CNFs. FeCoNi with atomic-level mixing of each element can effectively modulate lithium polysulfides (LiPSs), multiple components making them promising to catalyze more LiPSs species. The higher configurational entropy endows FeCoNi@CNFs with extraordinary electrochemical activity, corrosion resistance, and mechanical properties. The fractal structure of CNFs provides a large specific surface area, leaving room for volume expansion and Li₂S accumulation, facilitating electrolyte wetting. The unique 3D conductive network structure can suppress the shuttle effect by physicochemical adsorption of LiPSs. This work systematically evaluates the performance of the obtained Li₂S₆/FeCoNi@CNFs electrode. The initial discharge capacity of Li₂S₆/FeCoNi@CNFs reaches 1670.8 mAh g⁻¹ at 0.1 C under -20 °C. After 100 cycles at 0.2 C, the capacity decreases from 1462.3 to 1250.1 mAh g⁻¹. Notably, even under -40 °C at 0.1 C, the initial discharge capacity of Li₂S₆/FeCoNi@CNFs still reaches 1202.8 mAh g⁻¹. After 100 cycles at 0.2 C, the capacity retention rate is 50%. This work has important implications for the development of low-temperature Li-S batteries.     

Solvent Induced Activation Reaction of MoS2 Nanosheets within Nitrogen/Sulfur-Codoped Carbon Network Boosting Sodium Ion Storage

MoS₂, as a classical 2D material, becomes a capable anode candidate for sodium-ion batteries. However, MoS₂ presents a disparate electrochemical performance in the ether-based and ester-based electrolyte with unclear mechanism. Herein, tiny MoS₂ nanosheets embedded in nitrogen/sulfur-codoped carbon (MoS₂@NSC) networks are designed and fabricated through an uncomplicated solvothermal method. Thanks to the ether-based electrolyte, the MoS₂@NSC shows a unique capacity growth in the original stage of cycling. But in the ester-based electrolyte, MoS₂@NSC shows a usual capacity decay. The increasing capacity puts down to the gradual transformation from MoS₂ to MoS₃ with the structure reconstruction. Based on the above mechanism, MoS₂@NSC demonstrates an excellent recyclability and the specific capacity keeps around 286 mAh g⁻¹ at 5 A g⁻¹ after 5000 cycles with an ultralow capacity fading rate of only 0.0034% per cycle. In addition, a MoS₂@NSC‖Na₃V₂(PO₄)₃ full cell with ether-based electrolyte is assembled and demonstrates a capacity of 71 mAh g⁻¹, suggesting the potential application of MoS₂@NSC. Here the electrochemical conversion mechanism of MoS₂ is revealed in the ether-based electrolyte and significance of the electrolyte design on the promoting Na ion storage behavior is highlighted.     

Regulating Electrochemical Kinetics of CoP by Incorporating Oxygen on Surface for High-Performance Li–S Batteries

Lithium–sulfur (Li–S) batteries are widely studied because of their high theoretical specific capacity and environmental friendliness. However, the further development of Li–S batteries is hindered by the shuttle effect of lithium polysulfides (LiPSs) and the sluggish redox kinetics. Since the adsorption and catalytic conversion of LiPSs mainly occur on the surface of the electrocatalyst, regulating the surface structure of electrocatalysts is an advisable strategy to solve the obstacles in Li–S batteries. Herein, CoP nanoparticles with high oxygen content on surface embedded in hollow carbon nanocages (C/O-CoP) is employed to functionalize the separators and the effect of the surface oxygen content of CoP on the electrochemical performance is systematically explored. Increasing the oxygen content on CoP surface can enhance the chemical adsorption to lithium polysulfides and accelerate the redox conversions kinetics of polysulfides. The cell with C/O-CoP modified separator can achieve the capacity of 1033 mAh g⁻¹ and maintain 749 mAh g⁻¹ after 200 cycles at 2 C. Moreover, DFT calculations are used to reveal the enhancement mechanism of oxygen content on surface of CoP in Li–S chemistry. This work offers a new insight into developing high-performance Li–S batteries from the perspective of surface engineering.     

Design of High-Capacity MoS3 Decorated Nitrogen Doped Carbon Coated Cu2S Electrode Structures with Dual Heterogenous Interfaces for Outstanding Sodium-Ion Storage

The hierarchical Cu₂S@NC@MoS₃ heterostructures have been firstly constructed by the high-capacity MoS₃ and high-conductive N-doped carbon to co-decorate the Cu₂S hollow nanospheres. During the heterostructure, the middle N-doped carbon layer as the linker facilitates the uniform deposition of MoS₃ and enhances the structural stability and electronic conductivity. The popular hollow/porous structures largely restrain the big volume changes of active materials. Due to the cooperative effect of three components, the new Cu₂S@NC@MoS₃ heterostructures with dual heterogenous interfaces and small voltage hysteresis for sodium ion storage display a high charge capacity (545 mAh g⁻¹ for 200 cycles at 0.5 A g⁻¹), excellent rate capability (424 mAh g⁻¹ at 15 A g⁻¹) and ultra-long cyclic life (491 mAh g⁻¹ for 2000 cycles at 3 A g⁻¹). Except for the performance test, the reaction mechanism, kinetics analysis, and theoretical calculation have been performed to explain the reason of excellent electrochemical performance of Cu₂S@NC@MoS₃. The rich active sites and rapid Na⁺ diffusion kinetics of this ternary heterostructure is beneficial to the high efficient sodium storage. The assembled full cell matched with Na₃V₂(PO₄)₃@rGO cathode likewise displays remarkable electrochemical properties. The outstanding sodium storage performances of Cu₂S@NC@MoS₃ heterostructures indicate the potential applications in energy storage fields.     

Stable bismuth-antimony alloy cathode with a conversion-dissolution/deposition mechanism for high-performance zinc batteries

Although a large number of intercalation cathode materials for aqueous Zn batteries have been reported, limited intercalation capacity precludes achieving a higher energy density. Here we develop a high-performance aqueous Zn battery based on BiSb alloy (Bi_0.5Sb_0.5) using a high-concentrated strong-basic polyelectrolyte. We demonstrate that a conversion-dissolution/deposition electrochemical mechanism (BiSb ↔ Bi + SbO₂⁻ ↔ Bi + SbO₃⁻ ↔ Bi₂O₃) through in situ X-ray diffraction (XRD), Raman, and ex-situ X-ray photoelectron spectrometry (XPS) characterizations with the help of density functional theory calculations. The BiSb cathode delivers large capacity of 512 mAh g⁻¹ at 0.3 Ag⁻¹ and superior rate capability of 90 mAh g⁻¹ even at 20 Ag⁻¹, and long-term cyclability with capacity retentions of 184 mAh g⁻¹ after 600 cycles at 0.5 Ag⁻¹ and 130 mAh g⁻¹ after 1300 cycles at 1 Ag⁻¹. Remarkably, even at temperatures as low as −10 and −20 °C, capacities of 210 and 197 mAh g⁻¹ are reserved at 1 Ag⁻¹, respectively. Moreover, the prepared pouch Zn//BiSb battery delivers a high energy density of 303 Wh kg⁻¹_BiSb at 0.3 Ag⁻¹. When coupled with a high concentration polyelectrolyte, the Zn/BiSb battery exhibits an excellent performance over a wide temperature range (−40 to 40 °C). Our research reveals the metal cathode is promising for Zn batteries to achieve a high performance with the unique mechanism and alloys can be an effective approach to stabilize metal electrodes for cycling.     

Flower-Like NiS2/WS2 Heterojunction as Polysulfide/sulfide Bidirectional Catalytic Layer for High-Performance Lithium−Sulfur Batteries

The slow sulfur oxidation–reduction kinetics are one of the key factors hindering the widespread use of lithium–sulfur batteries (LSBs). Herein, flower-shaped NiS₂-WS₂ heterojunction as the functional intercalation of LSBs is successfully prepared, and effectively improved the reaction kinetics of sulfur. Flower-like nanospheres composed of ultra-thin nanosheets (≤10 nm) enhance quickly transfer of mass and charge. Meanwhile, the heterostructures simultaneously serve as an electron receptor and a donor, thereby simultaneously accelerating the bidirectional catalytic activity of reduction and oxidation reactions in the LSBs. In addition, the adsorption experiment, chemical state analysis of elements before and after the reaction and theoretical calculation have effectively verified that NiS₂-WS₂ heterojunction nanospheres optimize the adsorption capacity and bidirectional catalytic effect of polysulfides. The results show that the initial discharge capacity of NiS₂-WS₂ functional intercalation is as high as 1518.7 mAh g⁻¹ at 0.2 C. Even at a high current density of 5 C, it still shows a discharge specific capacity of 615.7 mAh g⁻¹, showing excellent rate performance. More importantly, the capacity is 258.9 mAh g⁻¹ after 1500 cycles at 5 C, and the attenuation per cycle is only 0.039%, and the Coulomb efficiency remains above 95%.     

Hybrid of spinel zinc-cobalt oxide nanospheres combined with nitrogen-containing carbon nanofibers as advanced electrocatalyst for redox reaction in lithium/polysulfides batteries

The polysulfides shuttle effect and torpid kinetic are of the crucial barriers for lithium/sulfur batteries. Herein, nitrogen-containing carbon nanofibers (NCFs) combined with spinel zinc-cobalt oxide (ZCO) nanospheres hybrid (denoted as ZCONCFs) were designed as membrane electrode containing Li₂S₆ catholyte for lithium/polysulfides batteries, which promote electrochemical performance by suppressing the shuttle effect and enhancing the redox kinetics of lithium polysulfides. The conductive NCFs provide fast electronic transport and anchored ZCO nanospheres possess a strong affinity to sulfur species, which could effectively anchor lithium polysulfides, boost their redox reaction catalytically-accelerate the reversible soluble/insoluble phases conversion process, and greatly improve the utilization of active material. The results show that ZCONCFs membrane electrode with 5 mg sulfur loading exhibited stability cycling capacity and improved reaction kinetics, which delivered a high initial capacity of 1160 mAh g^?1 at 0.2C and sustain a capacity of 830 mAh g^?1 after 300 cycles. The cell with ZCONCFs exhibits 8.22 mAh under the sulfur loading of 10 mg and the capacity decay rate is 0.11% per cycle after 150 cycles. This effective method could significantly improve the application capacity of lithium/sulfur batteries.     

Coordinating Interface Polymerization with Micelle Mediated Assembly Towards Two-Dimensional Mesoporous Carbon/CoNi for Advanced Lithium–Sulfur Battery

Lithium-sulfur battery has attracted significant attention by virtues of their high theoretical energy density, natural abundance, and environmental friendliness. However, the notorious shuttle effect of polysulfides intermediates severely hinders its practical application. Herein, a novel 2D mesoporous N-doped carbon nanosheet with confined bimetallic CoNi nanoparticles sandwiched graphene (mNC-CoNi@rGO) is successfully fabricated through a coordinating interface polymerization and micelle mediated co-assembly strategy. mNC-CoNi@rGO serves as a robust host material that endows lithium-sulfur batteries with a high reversible capacity of 1115 mAh g⁻¹ at 0.2 C after 100 cycles, superior rate capability, and excellent cycling stability with 679.2 mAh g⁻¹ capacity retention over 700 cycles at 1 C. With sulfur contents of up to 5.0 mg cm⁻², the area capacity remains to be 5.1 mAh cm⁻² after 100 cycles at 0.2 C. The remarkable performance is further resolved via a series of experimental characterizations combined with density functional theory calculations. These results reveal that the ordered mesoporous N-doped carbon-encapsulated graphene framework acts as the ion/electron transport highway with excellent electrical conductivity, while bimetallic CoNi nanoparticles enhance the polysulfides adsorption and catalytic conversion that simultaneously accelerate the multiphase sulfur/polysulfides/sulfides conversion and inhibit the polysulfides shuttle.     

Establishing Transition Metal Phosphides as Effective Sulfur Hosts in Lithium–Sulfur Batteries through the Triple Effect of “Confinement–Adsorption–Catalysis”

Structurally optimized transition metal phosphides are identified as a promising avenue for the commercialization of lithium–sulfur (Li–S) batteries. In this study, a CoP nanoparticle-doped hollow ordered mesoporous carbon sphere (CoP-OMCS) is developed as a S host with a “Confinement–Adsorption–Catalysis” triple effect for Li–S batteries. The Li-S batteries with CoP-OMCS/S cathode demonstrate excellent performance, delivering a discharge capacity of 1148 mAh g⁻¹ at 0.5 C and good cycling stability with a low long-cycle capacity decay rate of 0.059% per cycle. Even at a high current density of 2 C after 200 cycles, a high specific discharge capacity of 524 mAh g⁻¹ is maintained. Moreover, a reversible areal capacity of 6.56 mAh cm⁻² is achieved after 100 cycles at 0.2 C, despite a high S loading of 6.8 mg cm⁻². Density functional theory (DFT) calculations show that CoP exhibits enhanced adsorption capacity for sulfur-containing substances. Additionally, the optimized electronic structure of CoP significantly reduces the energy barrier during the conversion of Li₂S₄ (L) to Li₂S₂ (S). In summary, this work provides a promising approach to optimize transition metal phosphide materials structurally and design cathodes for Li–S batteries.     

Interface Density Engineering on Heterogeneous Molybdenum Dichalcogenides Enabling Highly Efficient Hydrogen Evolution Catalysis and Sodium Ion Storage

Constructing active heterointerfaces is powerful to enhance the electrochemical performances of transition metal dichalcogenides, but the interface density regulation remains a huge challenge. Herein, MoO₂/MoS₂ heterogeneous nanorods are encapsulated in nitrogen and sulfur co-doped carbon matrix (MoO₂/MoS₂@NSC) by controllable sulfidation. MoO₂ and MoS₂ are coupled intimately at atomic level, forming the MoO₂/MoS₂ heterointerfaces with different distribution density. Strong electronic interactions are triggered at these MoO₂/MoS₂ heterointerfaces for enhancing electron transfer. In alkaline media, the optimal material exhibits outstanding hydrogen evolution reaction (HER) performances that significantly surpass carbon-covered MoS₂ nanorods counterpart (η₁₀: 156 mV vs 232 mV) and most of the MoS₂-based heterostructures reported recently. First-principles calculation deciphers that MoO₂/MoS₂ heterointerfaces greatly promote water dissociation and hydrogen atom adsorption via the O–Mo–S electronic bridges during HER process. Moreover, benefited from the high pseudocapacitance contribution, abundant “ion reservoir”-like channels, and low Na⁺ diffusion barrier appended by high-density MoO₂/MoS₂ heterointerfaces, the material delivers high specific capacity of 888 mAh g⁻¹, remarkable rate capability and cycling stability of 390 cycles at 0.1 A g⁻¹ as the anode of sodium ion battery. This work will undoubtedly light the way of interface density engineering for high-performance electrochemical energy conversion and storage systems.