SnS Nanosheets Confined Growth by S and N Codoped Graphene with Enhanced Pseudocapacitance for Sodium-Ion Capacitors

Dual-Driven Ion/Electron Migration and Sodium Storage by In Situ Introduction of Copper Ions and a Carbon-Conductive Framework in a Tin-Based Sulfide Anode

Tin sulfide (SnS) has emerged as a promising anode material for sodium ion batteries (SIBs) due to its high theoretical capacity and large interlayer spacing. However, several challenges, such as severe insufficient electrochemical reactivity, rapid capacity degradation, and poor rate performance, still hinder its application in SIBs. In this study, in situ introduction of copper ions and a carbon conductive framework to form SnS nanocrystals embedded in a Cu2SnS3 lamellar structure heterojunction composite (SnS/Cu2SnS3/RGO) with graphene as the supporting material is proposed to achieve dual-driven sodium ion/electron migration during the continuous electrochemical process. The designed structure facilitates the preferential electrochemical reduction of copper ions into copper nanocrystals during the discharge process and functions as a catalytically active center to promote multivalence tin sodiation reaction. Furthermore, during the charging process, the presence of copper nanocrystals also facilitates efficient desodiation of NaxSn and further activates to form higher valence state sulfides. As a result, the SnS/Cu2SnS3/RGO composite demonstrates high cycling stability with a high reversible capacity of 395 mAh g-1 at 5A g-1 after 500 cycles with a capacity retention of 85.6%. In addition, the assembled Na3V2(PO4)3∥SnS/Cu2SnS3/RGO sodium ion full cell achieves 93.7% capacity retention after 80 cycles at 0.5 A g-1.

Gas Sensing Properties of PLD Grown 2D SnS Film: Effect of Film Thickness, Metal Nanoparticle Decoration, and In Situ KPFM Investigation

This study employs novel growth methodologies and surface sensitization with metal nanoparticles to enhance and manipulate gas sensing behavior of two-dimensional (2D)SnS film. Growth of SnS films is optimized by varying substrate temperature and laser pulses during pulsed laser deposition (PLD). Thereafter, palladium (Pd), gold (Au), and silver (Ag) nanoparticles are decorated on as-grown film using gas-phase synthesis techniques. X-ray diffraction (XRD), Raman spectroscopy, and Field-emission scanning electron microscopy (FESEM) elucidate the growth evolution of SnS and the effect of nanoparticle decoration. X-ray photoelectron spectroscopy (XPS) analyses the chemical state and composition. Pristine SnS, Ag, and Au decorated SnS films are sensitive and selective toward NO2 at room temperature (RT). Ag nanoparticle increases the response of pristine SnS from 48 to 138% toward 2 ppm NO2, which indicates electronic and chemical sensitization effect of Ag. Pd decoration on SnS tunes its selectivity toward H2 gas with a response of 55% toward 70 ppm H2 and limit of detection (LOD) < 1 ppm. In situ Kelvin probe force microscopy (KPFM) maps the work function changes, revealing catalytic effect of Ag toward NO2 in Ag-decorated SnS and direct charge transfer between Pd and SnS during H2 exposure in Pd-decorated SnS.

2D heterostructural Mn2O3 quantum dots embedded N-doped carbon nanosheets with strongly stable interface enabling high-performance sodium-ion hybrid capacitors

The ingenious architectural structural engineering is extensively identified as a cogent means for facilitating the electrochemical properties of conversion-type anode materials for sodium-ion storage. Herein, a delicate, scalable and controllable solvent-free strategy is proposed to synthesize ultrafine Mn2O3 quantum dots embedded into N-doped carbon to generate two-dimensional (2D) composites (MNC) with robust interfacial heterostructural interactions for high sodium ion storage and fast reaction kinetics, which averts the use of solvents and environmental pollution, greatly reduces time and production costs. The introduction of metallic Mn species simultaneously achieves the construction of ultrafine Mn2O3 quantum dots and strong interfacial heterostructural COMn bonds between metal species and 2D N-doped carbon matrix. The synergistic effect of the formation of oxide quantum dots, the combination of 2D N-doped carbon and the construction of robust interfacial interactions provides the stable electrode structure, fast reaction kinetics and high electrochemical storage capability of anode materials. Hence, MNC composites in SIBs convey remarkable reversible rate capability. Its superior capacity reaches 215 mAh g-1 for 50 cycles at 0.2 A g-1 and 155 mAh g-1 for 1000 cycles at a high current density of 5 A g-1, which shows good long-term stability. The assembled sodium-ion hybrid capacitors (SIHCs) device delivers outstanding energy density of 138 Wh kg-1 at a power density of 126 W kg-1 and 98% capacity retention after 2000 cycles at 2 A g-1, and tremendous capability for practical applications (69 LEDs can be easily lighted). This work not merely offers guidance for the rational interfacial engineering design of high-capacity Mn-based electrode materials in a feasible and scalable solvent-free tactics for Na+ storage, but also broadens the routes for projecting a better electrode material for other battery systems.

Lithium Azides Induced SnS Quantum Dots for Ultra-Fast and Long-Term Sodium Storage

Tin sulfide (SnS) is an attractive anode for sodium ion batteries (NIBs) because of its high theoretical capacity, while it seriously suffers from the inherently poor conductivity and huge volume variation during the cycling process, leading to inferior lifespan. To intrinsically maximize the sodium storage of SnS, herein, lithium azides (LiN3 )-induced SnS quantum dots (QDs) are first reported using a simple electrospinning strategy, where SnS QDs are uniformly distributed in the carbon fibers. Taking the advantage of LiN3 , which can effectively prevent the growth of crystal nuclei during the thermal treatment, the well-dispersed SnS QDs performs superior Na+ transfer kinetics and pseudocapacitive when used as an anode material for NIBs. The 3D SnS quantum dots embedded uniformly in N-doped nanofibers (SnS QDs@NCF) electrodes display superior long cycling life-span (484.6 mAh g-1 after 5800 cycles at 2 A g-1 and 430.9 mAh g-1 after 7880 cycles at 10 A g-1 ), as well as excellent rate capability (422.3 mAh g-1 at 20 A g-1 ). This fabrication of transition metal sulfides QDs composites provide a feasible strategy to develop NIBs with long life-span and superior rate capability to pave its practical implementation.

Sulfur-Bridged Bonds Heightened Na-Storage Properties in MnS Nanocubes Encapsulated by S-Doped Carbon Matrix Synthesized via Solvent-Free Tactics for High-Performance Hybrid Sodium Ion Capacitors

The exploitation of electrode materials with ability to balance capacity and kinetics between cathode and anode is a challenge for sodium-ion hybrid capacitors (SIHCs). Mn-based anode materials are limited by poor electrical conductivity, sluggish reaction kinetics, large volume variation, weak cycling stability, and inferior reversible capacity. Herein, MnS nanocubes encapsulated in S-doped porous carbon matrix (MSC) with strong sulfur-bridged bond interactions (CSMn) are successfully synthesized by solvent-free tactics. The CSMn bonds generated between MnS and carbon significantly inhibit the aggregation of nanostructural MnS cubes, restrict the volume expansion, and stabilize the nanostructure, which improves the Na⁺ storage reversibility and stability. Moreover, S-doped porous carbon enhances the electrical conductivity and electrons/ions diffusion rate, which boosts a fast kinetic reaction. As expected, MSC anode presents an outstanding reversible capacity of 600 mAh g^-1 at 0.2 A g^-1 and a long-term stable capacity of 357 mAh g^-1 for 1000 cycles at a high current density of 10 A g^-1 in sodium-ion batteries (SIBs). The as-assembled SIHCs deliver a high energy density of 109 W h kg^-1 and a high power output of 98 W kg^-1 , with 88% capacity retention at 2 A g^-1 after 2000 cycles and practical applications (55 LEDs can be lighted for 10 min).

Exploring 2D Energy Storage Materials: Advances in Structure, Synthesis, Optimization Strategies, and Applications for Monovalent and Multivalent Metal-Ion Hybrid Capacitors

The design and development of advanced energy storage devices with good energy/power densities and remarkable cycle life has long been a research hotspot. Metal-ion hybrid capacitors (MHCs) are considered as emerging and highly prospective candidates deriving from the integrated merits of metal-ion batteries with high energy density and supercapacitors with excellent power output and cycling stability. The realization of high-performance MHCs needs to conquer the inevitable imbalance in reaction kinetics between anode and cathode with different energy storage mechanisms. Featured by large specific surface area, short ion diffusion distance, ameliorated in-plane charge transport kinetics, and tunable surface and/or interlayer structures, 2D nanomaterials provide a promising platform for manufacturing battery-type electrodes with improved rate capability and capacitor-type electrodes with high capacity. In this article, the fundamental science of 2D nanomaterials and MHCs is first presented in detail, and then the performance optimization strategies from electrodes and electrolytes of MHCs are summarized. Next, the most recent progress in the application of 2D nanomaterials in monovalent and multivalent MHCs is dealt with. Furthermore, the energy storage mechanism of 2D electrode materials is deeply explored by advanced characterization techniques. Finally, the opportunities and challenges of 2D nanomaterials-based MHCs are prospected.

Zn-doped SnS with sulfur vacancies for enhanced photocatalytic hydrogen evolution from water

Tin sulfide has attracted considerable attention due to its adjustable optoelectronic properties. However, few present pieces of literature focus on the photocatalytic water splitting performance of stannous sulfide (SnS), despite...

Covalent Fixing of MoS2 Nanosheets with SnS Nanoparticles Anchored on g-C3N4/Graphene Boosting Fast Charge/Ion Transport for Sodium-Ion Hybrid Capacitors

The sluggish layered structural sodium reaction kinetics and the easy restacking property are major obstacles hindering the practical application of MoS₂-based electrodes for sodium storage. Herein, covalently assembled two-phase MoS₂-SnS supported by a hierarchical graphitic carbon nitride/graphene (MoS₂-SnS@g-C₃N₄/G) composite is constructed to improve cycling cyclability and rate performances for Na storage. The multiphase MoS₂-SnS@g-C₃N₄/G is featured with a covalent assembly strategy and an interconnected network architecture. This unique structural design can not only enhance the conductivity and facilitate fast interfacial electron transport, which is confirmed by experiments and density functional theory, but also buffer the volumetric changes of MoS₂-SnS. As a result, the as-obtained MoS₂-SnS@g-C₃N₄/G anode delivers a high reversible capacity of 834 mA h g^-1 at 0.1 A g^-1, a high rate capability of 452 mA h g^-1 at 5 A g^-1, and a long-term cycling stability (320 mA h g^-1 at 2 A g^-1 with 54.7% retention after 500 cycles) for the Na half-cell. Coupling with activated carbon (AC), our MoS₂-SnS@g-C₃N₄/G||AC sodium-ion hybrid capacitor delivers high energy/power densities (193.1 W h kg^-1/90 W kg^-1 and 41.5 W h kg^-1/18,000 W kg^-1) and a stable cycle life in the potential range of 0-4.0 V.

Strain Engineering in Electrochemical Activity and Stability of BiFeO3 Perovskites

Strain engineering is widely employed to manipulate the intrinsic relationship of activity and the crystal structure, while the mechanism and rational strategy toward high-performance devices are still under investigation. Here straining engineering is utilized to manipulate a series of a typical perovskite structures via introducing different types of heteroions (Bi_1-xM_xFeO₃, M = Ca²⁺ or Y³⁺ ion). The space group R3c in BiFeO₃ perovskites is found to be maintained with substituting a certain amount of heteroions at Bi³⁺ sites (<5%), while it would shift into either space groups P4mm (with Ca²⁺ substitute) or Pnma (with Y³⁺ substitute) beyond some critical doping amounts (>5%). Such a transformation is linked with the mismatched crystal strain induced by the heteroions substituted at Bi³⁺ sites, while the activity, stability, and energy storage capability of Bi_1-xM_xFeO₃ have been essentially varied. The results offer a strategy for manipulating stability and activity of perovskites in electrochemical energy conversion and storage.

Rational Design of Pillared SnS/Ti3C2Tx MXene for Superior Lithium-Ion Storage

MXenes have been widely explored in energy storage because of their extraordinary properties; however, the majority of research on their application was staged at multilayered MXenes or assisted by carbon materials. Scientifically speaking, the two most distinctive properties of MXenes are usually neglected, composed of large interlayer spacing and abundant surface chemistry, which distinguish MXenes from other two-dimensional materials. Herein, few-layered MXene (f-MXene) nanosheet powders can be easily prepared according to the modified solution-phase flocculation method, completely avoiding the restacking phenomenon of f-MXene nanosheets in preparation and oxidation issues during the storage process. Via further employing the solvothermal reaction and annealing treatment, we successfully constructed pillared SnS/Ti₃C₂T_x composites decorated with in situ formed TiO₂ nanoparticles. In the composites, MXenes can play the role of a conductive network, a buffer matrix for volume expansion of SnS, while the active SnS nanoplates can fully deliver the advantage of high capacity and further induce interlayer engineering of Ti₃C₂T_x during cycling. As a result, the pillared SnS/Ti₃C₂T_x MXene composites exhibit obvious improvement in electrochemical performance. Interestingly, there is an apparent enhancement of capacity at succedent cycling, which can be ascribed to the "pillar effect" of Ti₃C₂T_x MXenes. The efforts and attempts made in this work can further broaden the development of pillared MXene composites.

N-doped carbon-coated ultrasmall Nb2O5 nanocomposite with excellent long cyclability for sodium storage

Niobium pentoxide (Nb₂O₅) has drawn significant interest as a promising anode for sodium ion batteries (SIBs) due to its large interplanar lattice spacing and relatively high diffusion efficiency. However, the intrinsic drawbacks of low electrical conductivity and substantial volume change greatly impede its practical applications in large-scale energy storage systems. In this work, ultrasmall Nb₂O₅ nanoparticles wrapped with nitrogen-doped carbon (denoted as Nb₂O₅@NC) were delicately synthesized via a facile sol-gel method and subsequent heat treatment. The unique structure of ultrasmall Nb₂O₅ nanoparticles in a carbonaceous matrix can not only effectively shorten the transmission distance for both ions/electrons but also relieve the strain and stress caused by volume variation during the sodiation/desodiation process. In addition, the synergistic effect of nitrogen doping and carbon coating can further improve the electronic conductivity and pseudocapacitive behavior of the active materials, thus promoting the rapid electrochemical reaction kinetics of the Nb₂O₅@NC composite. The obtained 600-Nb₂O₅@NC-2 anode exhibits superior rate capability and outstanding cycling stability, delivering a reversible capacity of 196 mA h g^-1 at 1 A g^-1 after 1000 cycles. Even at high current densities of 5 A g^-1 and 10 A g^-1, the long-life cycling tests show that the reversible capacities still remain at 128.4 mA h g^-1 and 95.9 mA h g^-1 after 3000 cycles, respectively, which is the best performance of Nb₂O₅-based anodes at high current densities so far. These results indicate that the feasible synthetic strategy of Nb₂O₅@NC is an effective approach to develop high-performance Nb₂O₅-based anodes for large-scale energy storage.

Three-Dimensional Topotactic Host Structure-Secured Ultrastable VP-CNO Composite Anodes for Long Lifespan Lithium- and Sodium-Ion Capacitors

Performance degradation of lithium/sodium-ion capacitors (LICs/SICs) mainly originates from anode pulverization, particularly the alloying and conversion types, and has spurred research for alternatives with an insertion mechanism. Three-dimensional (3D) topotactic host materials remain much unexplored compared to two-dimensional (2D) ones (graphite, etc.). Herein, vanadium monophosphide (VP) is designed as a 3D topotactic host anode. Ex situ electrochemical characterizations reveal that there are no phase changes during (de)intercalation, which follows the topotactic intercalation mechanism. Computational simulations also confirm the metallic feature and topotactic structure of VP with a spacious interstitial position for the accommodation of guest species. To boost the electrochemical performance, carbon nano-onions (CNOs) are coupled with 3D VP. Superior specific capacity and rate capability of VP-CNOs vs lithium/sodium can be delivered due to the fast ion diffusion nature. An exceptional capacity retention of above 86% is maintained after 20 000 cycles, benefitting from the topotactic intercalation process. The optimized LICs/SICs exhibit high energy/power densities and an ultrastable lifespan of 20 000 cycles, which outperform most of the state-of-the-art LICs and SICs, demonstrating the potential of VP-CNOs as insertion anodes. This exploration would draw attention with regard to insertion anodes with 3D topotactic host topology and provide new insights into anode selection for LICs/SICs.

Recent Advances of Two-Dimensional Nanomaterials for Electrochemical Capacitors

Two-dimensional (2D) nanomaterials have drawn a wide range of research interests because of their unique ultrathin layered structures and attractive properties. In particular, the electrochemical properties and great variety of 2D nanomaterials make them highly attractive candidates for electrochemical capacitors, such as supercapacitors, lithium-ion capacitors, and sodium-ion capacitors. Herein, a comprehensive review of recent progress towards the application of 2D nanomaterials for electrochemical capacitors is provided. Several typical types of 2D nanomaterials are first briefly introduced, followed by detailed descriptions of their electrochemical capacitor applications. Finally, research perspectives and future research directions of these interesting areas are also provided.

Poplar flower-like nitrogen-doped carbon nanotube@VS4 composites with excellent sodium storage performance

As a new anode material for sodium-ion batteries (SIBs), VS₄ shows impressive energy storage potential due to its unique one-dimensional parallel chain structure, large chain spacing and high sulfur content.