CoNiO2 /Co4 N Heterostructure Nanowires Assisted Polysulfide Reaction Kinetics for Improved Lithium-Sulfur Batteries

SnS/SnS2 Heterostructures Embedded in Hierarchical Porous Carbon as Polysulfides Immobilizer for High-Performance Lithium-Sulfur Batteries

Driven by the strong adsorptive and catalytic ability of metal sulfides for soluble polysulfides, it is considered as a potential mediator to resolve the problems of shuttle effect and slow reaction kinetics of polysulfides in lithium-sulfur (Li-S) batteries. However, their further development is limited by poor electrical conductivity and bad long-term durability. Herein, one type of new catalyst composed of SnS/SnS2 heterostructures on hierarchical porous carbon (denoted as SnS/SnS2-HPC) by a simple hydrothermal method is reported and used as an interlayer coating on the conventional separator for blocking polysulfides. The SnS/SnS2-HPC integrates the advantages of a porous conductive network for promoting the transport of electrons and an enhanced electrocatalyst for accelerating polysulfides conversion. As a result, such a cell coupled with a SnS/SnS2-HPC interlayer exhibits a long-term lifespan of 1200 cycles. This work provides a new cell configuration by using heterostructures with a built-in electric field formed from a p-n heterojunction to improve the performance of Li-S batteries.

Formulation of Hierarchical Nanowire-Structured CoNiO2 and MoS2/CoNiO2 Hybrid Composite Electrodes for Supercapacitor Applications

Hierarchical porous nanowire-like MoS2/CoNiO2 nanohybrids were synthesized via the hydrothermal process. CoNiO2 nanowires were selected due to the edge site, high surface/volume ratio, and superior electrochemical characteristics as the porous backbone for decoration of layered MoS2 nanoflakes to construct innovative structure hierarchical three-dimensional (3D) porous NWs MoS2/CoNiO2 hybrids with excellent charge accumulation and efficient ion transport capabilities. Physicochemical analyses were conducted on the developed hybrid composite, revealing conclusive evidence that the CoNiO2 nanowires have been securely anchored onto the surface of the MoS2 nanoflake array. The electrochemical results strongly proved the benefit of the hierarchical 3D porous MoS2/CoNiO2 hybrid structure for the charge storage kinetics. The synergistic characteristics arising from the MoS2/CoNiO2 composite yielded a notably high specific capacitance of 1340 F/g at a current density of 0.5 A/g. Furthermore, the material exhibited sustained cycling stability, retaining 95.6% of its initial capacitance after 10 000 long cycles. The asymmetric device comprising porous MoS2/CoNiO2//activated carbon encompassed outstanding energy density (93.02 Wh/kg at 0.85 kW/kg) and cycling stability (94.1% capacitance retention after 10 000 cycles). Additionally, the successful illumination of light-emitting diodes underscores the significant potential of the synthesized MoS2/CoNiO2 (2D/1D) hybrid for practical high-energy storage applications.

Co/CoS2 Heterojunction Embedded in N, S-Doped Hollow Nanocage for Enhanced Polysulfides Conversion in High-Performance Lithium-Sulfur Batteries

Modulating the electronic configuration of the substrate to achieve the optimal chemisorption toward polysulfides (LiPSs) for boosting polysulfide conversion is a promising way to the efficient Li-S batteries but filled with challenges. Herein, a Co/CoS2 heterostructure is elaborately built to tuning d-orbital electronic structure of CoS2 for a high-performance electrocatalyst. Theoretical simulations first evidence that Co metal as the electron donator can form a built-in electric field with CoS2 and downshift the d-band center, leading to the well-optimized adsorption strength for lithium polysulfides on CoS2 , thus contributing a favorable way for expediting the redox reaction kinetics of LiPSs. As verification of prediction, a Co/CoS2 heterostructure implanted in porous hollow N, S co-doped carbon nanocage (Co/CoS2 @NSC) is designed to realize the electronic configuration regulation and promote the electrochemical performance. Consequently, the batteries assembled with Co/CoS2 @NSC cathode display an outstanding specific capacity and an admirable cycling property as well as a salient property of 8.25 mAh cm-2 under 8.18 mg cm-2 . The DFT calculation also reveals the synergistic effect of N, S co-doping for enhancing polysulfide adsorption as well as the detriment of excessive sulfur doping.

Dually Sulphophilic Chromium Boride Nanocatalyst Boosting Sulfur Conversion Kinetics Toward High-Performance Lithium-Sulfur Batteries

The sluggish kinetics of sulfur conversions have long been hindering the implementation of fast and efficient sulfur electrochemistry in lithium-sulfur (Li-S) batteries. In this regard, herein the unique chromium boride (CrB) is developed via a well-confined mild-temperature thermal reaction to serve as an advanced sulfur electrocatalyst. Its interstitial-alloy nature features excellent conductivity, while the nano-lamination architecture affords abundant active sites for host-guest interactions. More importantly, the CrB nanocatalyst demonstrates a dual sulphophilicity with simultaneous Cr─S and B─S bondage for establishing strong interactions with the intermediate polysulfides. As a result, significant stabilization and promotion of sulfur redox behavior can be achieved, enabling an excellent Li-S cell cyclability with a minimum capacity fading rate of 0.0176% per cycle over 2000 cycles and a favorable rate capability up to 7 C. Additionally, a high areal capacity of 5.2 mAh cm-2 , and decent cycling and rate performances are still attainable under high sulfur loading and low electrolyte dosage. This work offers a facile approach and instructive insights into metal boride sulfur electrocatalyst, holding a good promise for pursuing high-efficiency sulfur electrochemistry and high-performance Li-S batteries.

Symmetry or asymmetry: which one is the platform of nitrogen vacancies for alkaline hydrogen evolution

Conventional nitrogen vacancies with a symmetric coordination of metal cations (i.e., M1-Nv-M1) play a crucial role in tuning the local environment of the metal sites in metal nitrides and improving their electrochemical activity in the hydrogen evolution reaction (HER). However, the symmetric Nv sites, which feature a uniform charge distribution on adjacent metal sites, suffer from sluggish water dissociation kinetics and a poor capability for hydrogen desorption. Here, we fabricated Cr-doped and Nv-rich Co4N nanorods grown on a Ni foam (Cr-Co4N-Nv/NF) with asymmetric Cr-Nv-Co sites to effectively catalyze hydrogen evolution under alkaline conditions, with a low overpotential of 33 mV at a current density of 10 mA cm-2 and a small Tafel slope of 37 mV dec-1. The experimental characterizations and theoretical simulations collectively reveal that the construction of asymmetric Cr-Nv-Co sites gives rise to the upshift of the d-band center, thus promoting water adsorption and activation. Moreover, asymmetric Nv sites allow a balance between hydrogen adsorption and desorption, which avoids the limited desorption process over the symmetric Co-Nv-Co sites.

Effect of Heterostructure-Modified Separator in Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries with high energy density and low cost are the most promising competitor in the next generation of new energy reserve devices. However, there are still many problems that hinder its commercialization, mainly including shuttle of soluble polysulfides, slow reaction kinetics, and growth of Li dendrites. In order to solve above issues, various explorations have been carried out for various configurations, such as electrodes, separators, and electrolytes. Among them, the separator in contact with both anode and cathode is in a particularly special position. Reasonable design-modified material of separator can solve above key problems. Heterostructure engineering as a promising modification method can combine characteristics of different materials to generate synergistic effect at heterogeneous interface that is conducive to Li-S electrochemical behavior. This review not only elaborates the role of heterostructure-modified separators in dealing with above problems, but also analyzes the improvement of wettability and thermal stability of separators by modification of heterostructure materials, systematically clarifies its advantages, and summarizes some related progress in recent years. Finally, future development direction of heterostructure-based separator in Li-S batteries is given.

Manipulating Sulfur Conversion Kinetics through Interfacial Built-In Electric Field Enhanced Bidirectional Mott-Schottky Electrocatalysts in Lithium-Sulfur Batteries

Efficient electrocatalysts and catalytic mechanisms remain a pressing need in Li-S electrochemistry to address lithium polysulfide (LiPS) shuttling and enhance conversion kinetics. This study presents the development of multifunctional VO2@rGO heterostructures, incorporating interfacial built-in electric field (BIEF) enhancement, as a Mott-Schottky electrocatalyst for Li-S batteries. Electrochemical experiments and theoretical analysis demonstrate that the interfacial BIEF between VO2 and rGO induces self-driven charge redistribution, resulting in accelerated charge transport rates, enhanced LiPS chemisorption, reduced energy barriers for Li2S nucleation/decomposition, and improved Li-ion diffusion behavior. The Mott-Schottky electrocatalyst, combining the strengths of VO2's anchoring ability, rGO's metallic conductivity, and BIEF's optimized charge transport, exhibits an outstanding "trapping-conversion" effect. The modified Li-S battery with a VO2@rGO-modified separator achieves a highly reversible capacity of 558.0 mAh g-1 at 2 C over 600 cycles, with an average decay rate of 0.048% per cycle. This research offers valuable insights into the design of Mott-Schottky electrocatalysts and their catalytic mechanisms, advancing high-efficiency Li-S batteries and other multielectron energy storage and conversion devices.

High performance sulfur/carbon cathode for Na-S battery enabled by electrocatalytic effect of Sn-doped In2S3

Room-temperature sodium-sulfur (RT Na-S) batteries have been attracting enormous interests due to their low-cost, high capacity and environmental benignity. However, the shuttle effect and the sluggish electrochemical reaction activity of sodium polysulfides (NaPSs) seriously restrict their practical application. To solve these issues, we rationally designed an advanced Sn-doped In₂S₃/S/C cathode for RT Na-S batteries by magnetron sputtering in this work, which exhibited a high reversible capacity (1663.5 mAh g^-1 at 0.1 A g^-1) and excellent cycling performance (902.9 mAh g^-1 after 50 cycles). The in situ electrochemical impedance spectroscopy indicated that the Sn-doped In₂S₃ coating can accelerate charge-transfer kinetics and facilitate the diffusion of Na⁺. Furthermore, theoretical calculation revealed that doping of Sn into In₂S₃ can reduce the energy band gap, thus accelerating the electron transfer and promoting the electrochemical conversion of active species. It is demonstrated that adjusting the electronic structure is a reliable method to improve the electrocatalytic effect of catalyst and significantly improve the performance of S cathode in RT Na-S batteries.

Adsorption-catalysis design with cerium oxide nanorods supported nickel-cobalt-oxide with multifunctional reaction interfaces for anchoring polysulfides and accelerating redox reactions in lithium sulfur battery

The charge and discharge working mechanisms in lithium sulfur batteries contain multi-step complex reactions involving two-electron transfer and multiple phase transformations. The dissolution and diffusion of lithium polysulfides cause a huge loss of active material and fast capacity decay, preventing the practical use of lithium sulfur batteries. Herein, CeO₂ nanorods supported bimetallic nickel cobalt oxide (NiCo₂O_x) was investigated as a cathode host material for lithium sulfur batteries, which can provide adsorption-catalysis dual synergy to restrain the shuttle of polysulfides and stimulate rapid redox reaction for the conversion of polysulfides. The polar CeO₂ nanorods with abundant surface defects exhibit chemisorption towards lithium polysulfides and the excellent electrocatalytic activity of NiCo₂O_x nanoclusters can rev up the chain transformation of lithium polysulfides. The electrochemical results show that the battery with NiCo₂O_x/CeO₂ nanorods can demonstrate high discharge capacity, stable cycling, low voltage polarization and high sulfur utilization. The battery with NiCo₂O_x/CeO₂ nanorods unveils a high specific capacity of 1236 mAh g^-1 with a very low capacity fading of 0.09% per cycle after 100 cycles at a 0.2C current rate. Moreover, the excellent performance with high sulfur loading (>5 mg cm^-2) verifies a huge promise for future commercial applications.

Multiple Effects of High Surface Area Hollow Nanospheres Assembled by Nickel Cobaltate Nanosheets on Soluble Lithium Polysulfides

Inhibiting the shuttle effect of soluble polysulfides and improving slow reaction kinetics are key factors for the future development of Li-S batteries. Herein, edelweiss shaped NiCo₂O₄ hollow nanospheres with a high surface area were prepared by a simple template method to modify the separator to realize multiple physical constraints and strong chemical anchoring on the polysulfides. On one hand, the good electrolyte wettability of NiCo₂O₄ promoted the migration of Li-ions and greatly improved the dynamics. On the other hand, mesoporous NiCo₂O₄ nanomaterials provided many strong chemical binding sites for loading sulfur species. The hollow structure also provided a physical barrier to mitigate the sulfur species diffusion. Therefore, the modified separator realized multiple physical constraints and strong chemical anchoring on sulfur species. As a result, the sulfur cathode based on this composite separator showed significantly enhanced electrochemical performance. Even at 4 C, a high capacity of 505 mAh g^-1 was obtained, and about 80.6% could be retained after 300 cycles.

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

Lithium-sulfur (Li-S) batteries hold great promise for new-generation energy storage technologies owing to their overwhelming energy density. However, the poor conductivity of active sulfur and the shuttle effect limit their widespread use. Herein, a carbon cloth decorated with thiol-containing UiO-66 nanoparticles (CC@UiO-66(SH)₂) was developed to substitute the traditional interlayer and current collector for Li-S batteries. One side of CC@UiO-66(SH)₂ acts as a current collector to load active materials, while the other side serves as an interlayer to further restrain polysulfide shuttling. This two-in-one integrated architecture endows the sulfur cathode with fast electron/ion transport and efficient chemical confinement of polysulfides. More importantly, rich thiol groups in the pores of UiO-66(SH)₂ serve to tether polysulfides by both covalent interactions and lithium bonding. Therefore, the Li-S battery equipped with this integrated interlayer-current collector not only delivers an enhanced specific capability (1209 mAh g^-1 at 0.1 C) but also exhibits prominent cycling stability (an attenuation rate of 0.037% per cycle for 1000 cycles at 1 C). Meanwhile, the battery achieves a high discharge capacity of 795 mAh g^-1 at a sulfur loading of 3.83 mg cm^-2. The new metal-organic framework (MOF)-based electrode material reported in this study undoubtedly provides insights into the exploration of functional MOFs for robust Li-S batteries.