SnS2-CoS2@C nanocubes as high initial coulombic efficiency and long-life anodes for sodium-ion batteries

Electronic Promoter Breaks the Linear Scaling Relationship: Ultra-Rapid High-Temperature Synthesis of Heterostructured CoS/SnO2@C as a Bifunctional Oxygen Catalyst for Li-O2 Batteries

Li-O2 batteries urgently needs high discharge capacity and stable cycling performance, requiring effective and reliable bifunctional catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, Hovenia acerba Lindl-like heterostructure composed of cobalt sulfide and tin dioxide supported on carbon substrate (CoS/SnO2@C) is prepared via CO2 laser irradiation technology. The half-wave potential of CoS/SnO2@C for the ORR is 0.88 V, while the overpotential of the OER at 10 mA cm-2 is as low as 270 mV. The Li-O2 batteries employing the bifunctional CoS/SnO2@C catalyst displays a high discharge specific capacity of 3332.25 mAh g-1 and long cycling life of 226 cycles. Additionally, theory calculations demonstrate that the construction of heterostructure decreases energy barrier of the rate-determining step (RDS) for both ORR and OER. Notably, SnO2 behaves as the electronic promoter to optimize the electronic structure of heterostructure interface and triggers charge redistribution of CoS, which weakens the adsorption strength of the *O-intermediates and allows to break the linear scaling relationship, thus further enhancing the catalytic performance of CoS/SnO2@C. This research furnishes directions for the design of heterogeneous catalysts, highlighting its great potential for application in rechargeable Li-O2 batteries.

Synergistically Coupling Atomic-Level Defect-Manipulation and Nanoscopic-Level Interfacial Engineering Enables Fast and Durable Sodium Storage

Through inducing interlayer anionic ligands and functionally modifying conductive carbon-skeleton on the transition metal chalcogenides (TMCs) parent to achieve atomic-level defect-manipulation and nanoscopic-level architecture design is of great significance, which can broaden interlayer distance, optimize electronic structure, and mitigate structural deformation to endow high-efficiency battery performance of TMCs. Herein, an intriguing 3D biconcave hollow-tyre-like anode constituted by carbon-packaged defective-rich SnSSe nanosheet grafting onto Aspergillus niger spores-derived hollow-carbon (ANDC@SnSSe@C) is reported. Systematically experimental investigations and theoretical analyses forcefully demonstrate the existence of anion Se ligand and outer-carbon all-around encapsulation on the ANDC@SnSSe@C can effectively yield abundant structural defects and Na+-reactivity sites, accelerate rapid ion migration, widen interlayer spacing, as well as relieve volume expansion, thus further resolving the critical issues throughout the charge-discharge processes. As anticipated, as-fabricated ANDC@SnSSe@C anode contributes extraordinary reversible capacity, wonderful cyclic lifespan with 83.4% capacity retention over 2000 cycles at 20.0 A g-1, and exceptional rate capability. A series of correlated kinetic investigations and ex situ characterizations deeply reveal the underlying springheads for the ion-transport kinetics, as well as synthetically elucidate phase-transformation mechanism of the ANDC@SnSSe@C. Furthermore, the ANDC@SnSSe@C-based sodium ion full cell and hybrid capacitor offer high-capacity contribution and remarkable energy-density output, indicative of its great practicability.

Rod-like Ni-CoS2@NC@C: Structural design, heteroatom doping and carbon confinement engineering to synergistically boost sodium storage performance

Currently, conversion-type transition metal sulfides have been extensively favored as the anodes for sodium-ion batteries due to their excellent redox reversibility and high theoretical capacity; however, they generally suffer from large volume expansion and structural instability during repeatedly Na+ de/intercalation. Herein, spatially dual-confined Ni-doped CoS2@NC@C microrods (Ni-CoS2@NC@C) are developed via structural design, heteroatom doping and carbon confinement to boost sodium storage performance of the material. The morphology of one-dimensional-structured microrods effectively enlarges the electrode/electrolyte contact area, while the confinement of dual-carbon layers greatly alleviates the volume change-induced stress, pulverization, agglomeration of the material during charging and discharging. Moreover, the introduction of Ni improves the electrical conductivity of the material by modulating the electronic structure and enlarges the interlayer distance to accelerate Na+ diffusion. Accordingly, the as-prepared Ni-CoS2@NC@C exhibits superb electrochemical properties, delivering the satisfactory cycling performance of 526.6 mA h g-1 after 250 cycles at 1 A g-1, excellent rate performance of 410.9 mA h g-1 at 5 A g-1 and superior long cycling life of 502.5 mA h g-1 after 1,500 cycles at 5 A g-1. This study provides an innovative idea to improve sodium storage performance of conversion-type transition metal sulfides through the comprehensive strategy of structural design, heteroatom doping and carbon confinement.

Heterostructured CoS2/SnS2 encapsulated in sulfur-doped carbon exhibiting high potassium ion storage capacity

Metallic sulfides are currently considered as ideal anode materials for potassium-ion batteries by virtue of their high specific capacities. However, their low intrinsic electronic conductivity, large volume variation and dissolution of polysulfides in electrochemical reactions hinder their further development toward practical applications. Here, we propose an effective structural design strategy by encapsulating CoS2/SnS2 in sulfur-doped carbon layers, in which internal voids are created to relieve the strain in the CoS2/SnS2 core, while the sulfur-doped carbon layer serves to improve the electron transport and inhibit the dissolution of polysulfides. These features enable the as-designed anode to deliver a high specific capacity (520 mAh/g at 0.1 A/g), a high rate capability (185 mA h g-1 at 10 A/g) and lifespan (0.016 % capacity loss per cycle up to 1500 cycles). Our comprehensive electrochemical characterization reveals that the heterostructure of CoS2/SnS2 not only promotes charge transfer at its interfaces, but also enhances the rate of K+ diffusion. Additionally, potassium-ion capacitors based on this novel anode are able to attain an energy density up to 162 Wh kg-1 and ∼ 96 % capacity retention after 3000 cycles at 10 A/g.The demonstrated design rule combining morphological and structural engineering strategies sheds light on the development of advanced electrodes for high performance potassium-based energy storage devices.

Homologous Heterostructured NiS/NiS2 @C Hollow Ultrathin Microspheres with Interfacial Electron Redistribution for High-Performance Sodium Storage

Nickel sulfides with high theoretical capacity are considered as promising anode materials for sodium-ion batteries (SIBs); however, their intrinsic poor electric conductivity, large volume change during charging/discharging, and easy sulfur dissolution result in inferior electrochemical performance for sodium storage. Herein, a hierarchical hollow microsphere is assembled from heterostructured NiS/NiS2 nanoparticles confined by in situ carbon layer (H-NiS/NiS2 @C) via regulating the sulfidation temperature of the precursor Ni-MOFs. The morphology of ultrathin hollow spherical shells and confinement of in situ carbon layer to active materials provide rich channels for ion/electron transfer and alleviate the effects of volume change and agglomeration of the material. Consequently, the as-prepared H-NiS/NiS2 @C exhibit superb electrochemical properties, satisfactory initial specific capacity of 953.0 mA h g-1 at 0.1 A g-1 , excellent rate capability of 509.9 mA h g-1 at 2 A g-1 , and superior longtime cycling life with 433.4 mA h g-1 after 4500 cycles at 10 A g-1 . Density functional theory calculation shows that heterogenous interfaces with electron redistribution lead to charge transfer from NiS to NiS2 , and thus favor interfacial electron transport and reduce ion-diffusion barrier. This work provides an innovative idea for the synthesis of homologous heterostructures for high-efficiency SIB electrode materials.

Prussian Blue Analogue-Derived Fe-Doped CoS2 Nanoparticles Confined in Bayberry-like N-Doped Carbon Spheres as Anodes for Sodium-Ion Batteries

Obvious volume change and the dissolution of polysulfide as well as sluggish kinetics are serious issues for the development of high performance metal sulfide anodes for sodium-ion batteries (SIBs), which usually result in fast capacity fading during continuous sodiation and desodiation processes. In this work, by utilizing a Prussian blue analogue as functional precursors, small Fe-doped CoS2 nanoparticles spatially confined in N-doped carbon spheres with rich porosity were synthesized through facile successive precipitation, carbonization, and sulfurization processes, leading to the formation of bayberry-like Fe-doped CoS2/N-doped carbon spheres (Fe-CoS2/NC). By introducing a suitable amount of FeCl3 in the starting materials, the optimal Fe-CoS2/NC hybrid spheres with the designed composition and pore structure exhibited superior cycling stability (621 mA h g−1 after 400 cycles at 1 A g−1) and improved the rate capability (493 mA h g−1 at 5 A g−1). This work provides a new avenue for the rational design and synthesis of high performance metal sulfide-based anode materials toward SIBs.

Spatially Guided Assembly of Polyoxometalate Superlattices and Their Derivatives as High-Power Sodium-Ion Battery Anodes

The use of polyoxometalate clusters (POMs) with multitudinous structures and surface properties as building blocks has sparked the development of cluster-assembled materials with many prospective applications. In comparison to classic molecules and assembly processes, control over the steric interactions and linkage of large POMs to achieve superlattices with multiple levels of organization remains a great challenge. This work presents a universal approach to modulate the spatial coordination behavior and configurations, and achieves a class of cluster superlattice architectures formed by linear alignment and two-dimensional arrangement of POM units. The formation mechanism is explained as a stepwise co-assembly pathway in which POMs can intervene and dictate a typical stripping-restacking combination mode with the lamellar mediator. These cluster superlattices with long-range POMs ordering impart distinct merits to their derivatives by sulfuration, for which we demonstrate the substantially promoted power and cycling life of these POM derivatives applied as sodium-ion battery anodes.

CoS2-decorated CdS nanorods for efficient degradation of organic pollutants

The heterostructure between CoS2 and CdS can improve the charge separation efficiency during photocatalysis and promote the generation of more OH and O2− radicals under light irradiation.

Electrolyte/Structure-Dependent Cocktail Mediation Enabling High-Rate/Low-Plateau Metal Sulfide Anodes for Sodium Storage

As promising anodes for sodium-ion batteries, metal sulfides ubiquitously suffer from low-rate and high-plateau issues, greatly hindering their application in full-cells. Herein, exemplifying carbon nanotubes (CNTs)-stringed metal sulfides superstructure (CSC) assembled by nano-dispersed SnS₂ and CoS₂ phases, cocktail mediation effect similar to that of high-entropy materials is initially studied in ether-based electrolyte to solve the challenges. The high nano-dispersity of metal sulfides in CSC anode underlies the cocktail-like mediation effect, enabling the circumvention of intrinsic drawbacks of different metal sulfides. By utilizing ether-based electrolyte, the reversibility of metal sulfides is greatly improved, sustaining a long-life effectivity of cocktail-like mediation. As such, CSC effectively overcomes low-rate flaw of SnS₂ and high-plateau demerit of CoS₂, simultaneously realizes a high rate and a low plateau. In half-cells, CSC delivers an ultrahigh-rate capability of 327.6 mAh g^-1_anode at 20 A g^-1, far outperforming those of monometallic sulfides (SnS₂, CoS₂) and their mixtures. Compared with CoS₂ phase and SnS₂/CoS₂ mixture, CSC shows remarkably lowered average charge voltage up to ca. 0.62 V. As-assembled CSC//Na_1.5VPO_4.8F_0.7 full-cell shows a good rate capability (0.05 ~ 1.0 A g^-1, 120.3 mAh g^-1_electrode at 0.05 A g^-1) and a high average discharge voltage up to 2.57 V, comparable to full-cells with alloy-type anodes. Kinetics analysis verifies that the cocktail-like mediation effect largely boosts the charge transfer and ionic diffusion in CSC, compared with single phase and mixed phases. Further mechanism study reveals that alternative and complementary electrochemical processes between nano-dispersed SnS₂ and CoS₂ phases are responsible for the lowered charge voltage of CSC. This electrolyte/structure-dependent cocktail-like mediation effect effectively enhances the practicability of metal sulfide anodes, which will boost the development of high-rate/-voltage sodium-ion full batteries.