1T-Phase MoS2 with large layer spacing supported on carbon cloth for high-performance Na+ storage

Nitrogen plasma-induced phase engineering and titanium carbide/carbon nanotubes dual conductive skeletons endow molybdenum disulfide with significantly improved lithium storage performance

MoS2/Ti3C2 MXene composite has emerged as a promising anode material for lithium storage due to the synergistic combination of high specific capacity offered by MoS2 and conductive skeleton provided by Ti3C2 MXene. However, its two-dimensional/two-dimensional (2D/2D) structure is susceptible to collapse after long cycles, while the inherent low conductivity of MoS2 limits its rate performance. In this study, we developed a novel approach combining plasma-induced phase engineering with dual skeleton structure design to fabricate a unique P-MoS2/Ti3C2/CNTs anode material featuring highly conductive 1T phase MoS2 and a stable one-dimensional/two-dimensional (1D/2D) architecture. Within this architecture, growth of MoS2 nanosheets on the surface of Ti3C2 cross-linked by carbon nanotubes (CNTs) was achieved. The resulting Ti3C2/CNTs dual skeleton not only provides robust mechanical support to prevent structural collapse during long cycles but also offers increased specific surface area and additional Li+ storage space, thereby enhancing the lithium storage capacity of the composite. Subsequent N2 plasma treatment induced a phase transition in MoS2 from 2H to 1T configuration. Density functional theory (DFT) calculations confirmed that the induced 1T-MoS2 exhibits higher conductivity and lower Li+ diffusion barrier compared to 2H-MoS2. Benefiting from these synergistic effects, our P-MoS2/Ti3C2/CNTs anode demonstrated remarkable electrochemical performance including a high reversible specific capacity of 1120 mAh g-1 at 0.1 A g-1, excellent cycling stability with a specific capacity retention of 670 mAh g-1 after 600 cycles at 1 A/g, and superior rate performance with a specific capacity of 614 mAh g-1 at 2 A g-1. This combined modification strategy will serve as guidance for designing other energy storage materials.

High-performance flexible asymmetric supercapacitor based on hierarchical MnO2/PPy nanocomposites covered MnOOH nanowire arrays cathode and 3D network-like Fe2O3/PPy hybrid nanosheets anode

The configuration of asymmetric supercapacitors (ASCs) has proven to be an effective approach to increase the energy storage properties due to the expanded working voltage resulting from the well-separated potential windows of the cathode and anode. However, carbonaceous anode materials generally suffer from relatively low capacitance, which restricts the enhancement of the energy storage performance of the full device in a traditional asymmetrical design. Herein, a rational design of all-pseudocapacitive ASCs (APASCs) using pseudocapacitive materials with a novel hierarchical nanostructure on both electrodes was developed to optimize the electrochemical properties for high-performance ASC devices. The assembled APASC employed the MnO2/PPy nanocomposites covered MnOOH nanowire arrays with core-shell hierarchical architecture as the cathode and Fe2O3/PPy hybrid nanosheets with 3D porous network-like structure as the anode. Owing to the coordinated pseudocapacitive properties and unique hierarchical nanostructures, this assembled APASC exhibited an exceptional volumetric capacitance of 4.92F cm-3 in a stable voltage window of 2 V, a maximum volumetric energy density of 2.66 mWh cm-3 at 19.72 mW cm-3, and excellent cyclic stability over 10,000 cycles (90.6 % capacitance retention), as well as remarkable flexibility and mechanical stability, providing insights for the design of flexible energy storage systems with enhanced performance.

Ultrahigh initial coulombic efficiency for deep sodium storage enabled by carbon-free vanadium-doping MoS2 hierarchical nanostructure

Molybdenum disulfide (MoS2) has garnered attention as a promising anode material for sodium-ion batteries due to its high theoretical capacity and unique lamellar texture. Nevertheless, unmodified MoS2 suffers from inferior electrical conductivity, poor reaction reversibility, and suboptimal cycle life upon repeated sodiation/desodiation. In this study, a novel carbon-free V-heteroatom doping MoS2 composite (abbr. VMS) with hierarchical laurustinus-like structure was synthesized by a facile one-step hydrothermal process. Specifically, the rational doping of V-atoms can effectively modulate the intrinsic electronic structure of pure MoS2, resulting in enhanced Na-ion diffusion rate, improved reaction kinetics and reduced activation energy compared to bare MoS2. Additionally, the hierarchical structure of the VMS composite, with sufficient spacing, effectively mitigates mechanical stress and ensures the integrity of active materials. Consequently, the prepared VMS composite possesses exceptional reaction reversibility (average ICE value of 92 %) and remarkable capacity retention (92.1 % after 450 cycles at 10 A/g). These findings contribute valuable insights into the development of advanced MoS2-based anode for sodium ion batteries.

Interface strong-coupled 3D Mo-NiS@Ni-Fe LDH flower-cluster as exceptionally efficient electrocatalyst for water splitting in wide pH range

It is crucial to create a bifunctional catalyst with high efficiency and low cost for electrochemical water splitting under alkaline and neutral pH conditions. This study investigated the in-situ creation of ultrafine Mo-NiS and NiFe LDH nanosheets as an effective and stable electrocatalyst with a three-dimensional (3D) flower-cluster hierarchical structure (Mo-NiS@NiFe LDH). The strong interfacial connection between Mo-NiS and NiFe LDH enhances the formation of metal higher chemical states in the material, optimizes the electronic structure, increases OH^- adsorption capacity improves electron transfer/mass diffusion, and promotes O₂/H₂ gas release. As a result, at 10 mA cm^-2, Mo-NiS@NiFe LDH/NF demonstrates the outstanding bifunctional electrocatalytic activity of just 107 mV (HER, hydrogen evolution reaction) and 184 mV (hydrogen evolution reaction) (OER, oxygen evolution reaction). The catalytic performance is remarkably stable after 72 h of continuous operation in 1 M KOH at high current densities (300 mA cm^-2). More interestingly, in the overall water splitting system, the cell voltages for anode and cathode in both alkaline and neutral electrolytes for Mo-NiS@NiFe LDH/NF are only 1.54 V (alkaline) and 2.06 V (neutral) at 10 mA cm^-2. These results demonstrated that the bifunctional electrocatalyst design concept is a viable solution for water splitting in both alkaline and neutral systems.

Nickel sulfide/nickel phosphide heterostructures anchored on porous carbon nanosheets with rapid electron/ion transport dynamics for sodium-ion half/full batteries

Nickel-based materials have been extensively deemed as promising anodes for sodium-ion batteries (SIBs) owing to their superior capacity. Unfortunately, the rational design of electrodes as well as long-term cycling performance remains a thorny challenge due to the huge irreversible volume change during the charge/discharge process. Herein, the heterostructured ultrafine nickel sulfide/nickel phosphide (NiS/Ni₂P) nanoparticles closely attached to the interconnected porous carbon sheets (NiS/Ni₂P@C) are designed by facile hydrothermal and annealing methods. The NiS/Ni₂P heterostructure promotes ion/electron transport, thus accelerating the electrochemical reaction kinetics benefited from the built-in electric field effect. Moreover, the interconnected porous carbon sheets offer rapid electron migration and excellent electronic conductivity, while releasing the volume variance during Na⁺ intercalation and deintercalation, guaranteeing superior structural stability. As expected, the NiS/Ni₂P@C electrode exhibits a high reversible specific capacity of 344 mAh g^-1 at 0.1 A g^-1 and great rate stability. Significantly, the implementation of NiS/Ni₂P@C//Na₃(VPO₄)₂F₃ SIB full cell configuration exhibits relatively satisfactory cycle performance, which suggests its widely practical application. This research will develop an effective method for constructing heterostructured hybrids for electrochemical energy storage.

Sodium titanium phosphate nanocube decorated on tablet-like carbon for robust sodium storage performance at low temperature

Sodium-ion batteries, featuring resource abundance and similar working mechanisms to lithium-ion batteries, have gained extensive interest in both scientific exploration and industrial applications. However, the extremely sluggish reaction kinetics of charge carrier (Na+) at subzero temperatures significantly reduces their specific capacities and cycling life. Herein, this study presents a novel hybrid structure with sodium titanium phosphate (NaTi2(PO4)3, NTP) nanocube in-situ decorated on tablet-like carbon (NTP/C), which manifests superior sodium storage performances at low temperatures. At even -25 °C, a stable cycling with a specific capacity of 94.3 mAh/g can still be maintained after 200 cycles at 0.5 A/g, delivering a high capacity retention of 91.5 % compared with that at room temperature, along with an excellent rate capability. Generally, the superionic conductor structure, flat voltage plateaus, as well as the conductive carbonaceous framework can efficiently facilitate the charge transfer, accelerate the diffusion of Na+, and decrease the electrochemical polarization. Moreover, further investigations on diffusion kinetics, solid electrolyte interface layer, and the interaction between NTP and carbonaceous skeleton reveal its high Na+ diffusion coefficient, robust solid electrolyte interface, and strong electronic interaction, thus contributing to the superior capacity retentions at subzero temperatures.

Morphology-controlled synthesis of MoS2 using citric acid as a complexing agent and self-assembly inducer for high electrochemical performance

Two-dimensional MoS2 with a controllable morphology was prepared via a simple one-step hydrothermal method. Citric acid was used as a complexing agent and self-assembly inducer. The morphology of MoS2 changed from clusters to nanosheets, and, eventually, to stacked nanorods. A formation mechanism is proposed for the observed evolution of the morphology. The nanosheet structure presents a relatively large specific surface area, more exposed active sites and greater 1T phase content compared to the other morphologies. The electrochemical performance tests show that the MoS2 nanosheets exhibit excellent electrochemical behavior. Their specific capacitance is 320.5 F g-1, and their capacitance retention is up to 95% after 5000 cycles at 5 mA cm-2. This work provides a feasible approach for changing the morphology of MoS2 for high efficiency electrode materials for supercapacitors.

Fe-VS2 Electrocatalyst with Organic Matrix-Mediated Electron Transfer for Highly Efficient Nitrogen Fixation

Electrochemical N₂ fixation is considered to be a promising alternative to Haber-Bosch technology. Inspired by the composition and structure of natural nitrogenase, Fe-doped VS₂ nanosheets were prepared via one-step solvothermal method. The electron transfer system mediated by organic conductive polymer (1-AAQ-PA) was constructed to promote the electron transfer between Fe-VS₂ nanosheets and the electrode in electrocatalytic N₂ reduction reaction (NRR). The obtained 1-AAQ-PA-Fe-VS₂ electrode converted N₂ to NH₃ with a yield of 31.6 μg h^-1  mg^-1 at -0.35 V vs. reversible hydrogen electrode and high faradaic efficiency of 23.5 %. The introduction of Fe dopants favored N₂ adsorption and activation, while the Li-S bond between Fe-VS₂ and Li₂ SO₄ effectively inhibited hydrogen evolution. The highly efficient electron utilization in the electrocatalytic NRR process was realized using the 1-AAQ-PA as the electron transfer medium. Density functional theory calculations showed that N₂ was preferentially adsorbed on Fe and reduced to NH₃ via both distal and alternating mechanism.

Design of reduced graphene oxide coating carbon sub-microspheres hierarchical nanostructure for ultra-stable potassium storage performance

The development of high-performance carbon-based anode materials is still a significant challenge for K-ion storage. In our work, we designed reduced graphene oxide coating carbon sub-microspheres hierarchical nanostructure (CS@RGO) hierarchical nanostructure via a simple freeze-drying and subsequent pyrolysis as anode for K-ion batteries (KIBs), which presented an excellent electrochemical performance for K-ion storage, with a reversible specific capacity of 295 mAh g^-1 after 100 cycles at 100 mAh g^-1. Even at a high current density of 1 A g^-1, our CS@RGO still achieves ultra-stable K-ion storage of 200 mAh g^-1 at 1 A g^-1 after 5000 cycles almost without capacity fade. According to the galvanostatic intermittent titration technique result, the CS@RGO hybrid receives a high average diffusion coefficient of 7.35 × 10^-8 cm² s^-1, contributing to the rapid penetration of K-ion, which facilitates the enhancement of electrochemical performance for KIBs. Besides, we also use Raman spectra to investigate the electrochemical behavior of our CS@RGO hybrid for K-ion storage and confirm the reaction process. We believe that our work will offer the opportunity to enable ultra-stable carbon-based materials by the structure design in the K-ion battery field.

Rational nanostructured FeSe2 wrapped in nitrogen-doped carbon shell for high-rate capability and long cycling sodium-ion storage

Transition metal selenides (TMSs) have drawn substantial attention as promising anode materials for sodium-ion batteries (SIBs) on account oftheir rapid reaction kinetics and high reversible capacity. However, the undesirable capacity decay and inferior rate performance still hamper their large-scale application. Herein, an anode material comprising combination of olivary nanostructure FeSe₂ core and nitrogen-doped carbon shell (designated as FeSe₂@NC) is well designed by in-situ polymerization and selenization method. The well-designed nitrogen-doped carbon shell can not only alleviate the volume variation during the electrode cycling but also provide an optimized ion/electron transport pathway. The resulting FeSe₂@NC electrodes exhibit a superior rate capability of 228.4 mA h g^-1 at 10 A g^-1 and a long cycling performance of 246.5 mA h g^-1 at 5 A g^-1 after 1000 cycles, which can be assigned to the enhanced structural integrity and improved electrical conductivity. The strategy would present a promising thought for structure design of TMSs as anode materials, which could enhance high-rate and long-lasting cycle performances for SIBs.

Interlayer-expanded VS2 nanosheet: Fast ion transport, dynamic mechanism and application in Zn2+ and Mg2+/Li+ hybrid batteries systems

Currently, the development of polyvalent ions battery systems are still restricted by lacking suitable cathode materials with high energy density and long cycle life attributing to sluggish kinetic mechanism and of polyvalent ions. Herein, an effective inter-layer scaling strategy is proposed by using a simple hydrothermal method. The super layer spacing VS₂ (∼1 nm) cathode dramatically improves electrochemical performance of zinc-ion batteries (ZIBs) and magnesium/lithium hybrid ion batteries (MLIBs). The specific discharge capacities of ZIBs and MLIBs are 450.7 and 488.8 mA h g^-1 at current density of 0.1 A g^-1 which are much higher than the same type of battery systems. Finally, the diffusion mechanism and the corresponding theoretical model is established by adopting first principles. In brief, the work provides an effective strategy for the large scale application of multivalent and hybrid batteries systems.

Heterostructure engineering of ultrathin SnS2/Ti3C2Tx nanosheets for high-performance potassium-ion batteries

Layered metal sulfides are considered as promising candidates for potassium ion batteries (KIBs) owing to the unique interlayer passages for ion diffusion. However, the insufficient electronic conductivity, inevitable volume expansion, and sulfur loss hinder the promotion of K-ion storage performance. Herein, few-layered Ti₃C₂T_x nanosheets were selected as the multi-functional substrate for cooperating few-layered SnS₂ nanosheets, constructing SnS₂/Ti₃C₂T_x hetero-structural nanosheets (HNs) with the thickness as thin as about 5 nm. In this configuration, the formed Ti-S bonds provide robust interaction between SnS₂ and Ti₃C₂T_x nanosheets, which hinders the agglomeration of SnS₂ and the restack of Ti₃C₂T_x, endowing the hybrid material with robust nanostructure. Thus, the shortcomings of the SnS₂ anode are muchly relieved. In this way, the as-prepared SnS₂/Ti₃C₂T_x HNs electrode delivers reversible capacities of 462.1 mAh g^-1 at 0.1 A g^-1 and 166.1 mAh g^-1 at 2.0 A g^-1, respectively, and a capacity of 85.5 mAh g^-1 is remained even after 460 cycles at 2.0 A g^-1. These results are superior to those of the counterpart electrode, confirming aggressive promotion of K-ion storage performance of SnS₂ anode brought by the cooperation of Ti₃C₂T_x, and presenting a reliable strategy to improve the electrochemical performance of sulfide anodes.

Coal-Derived Graphene/MoS2 Heterostructure Electrodes for Li-Ion Batteries: Experiment and Simulation Study

A novel coal-derived graphene-intercalated MoS₂ heterostructure was prepared with a facile in situ hydrothermal approach followed by high-temperature calcination. XRD, FE-SEM, HR-TEM, HR-Raman, and TOC analytical instruments, combined with first-principles simulations, were employed to explore the structural and electrochemical properties of this heterostructure for use as an electrode material. The XRD measurements and simulations confirmed the formation of the MoS₂/graphene (MoS₂-G) heterostructure. The microstructure analysis indicated that a well-defined 3D flower-like structure with tunable interlayer distances was created in the MoS₂ layer. The novel MoS₂-09% G anode exhibits a remarkable initial discharge capacity of ∼929 mAh/g due to its interlayer expansion from the intercalation of graphene between the MoS₂ layers. This anode maintains a capacity of ∼813 mAh/g with a Coulombic efficiency (CE) of ∼99% after 150 cycles at a constant current density of 100 mA/g. This anode also delivers a high-rate capability of ∼579 mAh/g at a current density of 2000 mA/g, significantly higher than that of other comparable structures. The unique flower-like arrangement, sufficient interlayer spacing for Li-ion diffusion, and the increased conductive matrix created using coal-derived graphene enhance the electrode kinetics during electrochemical reactions. Our first-principles calculations revealed that the diffusion barriers are significantly lower in heterostructures compared to that of bare MoS₂. This heterostructure design has significant potential as a new type of anode for Li-ion storage in next-generation batteries.

Covalent Pinning of Highly Dispersed Ultrathin Metallic-Phase Molybdenum Disulfide Nanosheets on the Inner Surface of Mesoporous Carbon Spheres for Durable and Rapid Sodium Storage

Two-dimensional (2D) transition-metal dichalcogenide materials show potential for use in alkali metal ion batteries owing to their remarkable physical and chemical properties. Nevertheless, the electrochemical energy storage performance is still impaired by the tendency of aggregation, volume, and morphological change during the conversion reaction and poor intrinsic conductivity. Until now, ultrathin molybdenum disulfide nanosheets with a metallic-phase structure on the inner surface of mesoporous hollow carbon spheres (M-MoS₂@HCS) have rarely been investigated as an anode for sodium-ion batteries. In this work, a novel M-MoS₂@HCS anode was designed and synthesized by employing a template-assisted solvothermal reaction. Structural and chemical analyses indicate that the M-MoS₂ nanosheets with a larger interlayer spacing compared to their semiconductor counterpart grow on the inner surface of HCS via covalent interactions. When used as the anode materials for Na⁺ storage, the M-MoS₂@HCS anode presents durable and rapid sodium storage properties. The developed electrode shows a reversible capacity of 291.2 mAh g^-1 at a high current density of 5 A g^-1. After 100 cycles at 0.1 A g^-1, the reversible capacity is 401.3 mAh g^-1 with a capacity retention rate of 79%. After 2500 cycles at 1.0 A g^-1, the electrode still delivers a reversible capacity of 320.1 mAh g^-1 with a capacity retention rate of 75%. The excellent sodium storage capability of the MoS₂@HCS electrode is explained by the special structural design, which reveals great potential to accelerate the practical applications of transition-metal dichalcogenide electrodes for sodium storage.

Metal-organic framework derived vanadium-doped TiO2@carbon nanotablets for high-performance sodium storage

Titanium dioxide (TiO₂) as a potential anode material for sodium-ion batteries (SIBs) suffers from the intrinsic poor electronic conductivity and sluggish ionic diffusivity, thus usually leading to the inferior electrochemical performance. Herein, we demonstrate a facile strategy to enhance the sodium storage performance of TiO₂via vanadium (V) doping, using the pre-synthesized V-doped Ti-based metal-organic framework (MOF, MIL-125) as the precursor, which can be converted into the V-doped TiO₂ with simultaneous carbon hybridization and controlled V-doping amount (denote as V_xTiO₂@C, where × represents the V/Ti molar ratio (R_V/Ti)). V-doping not only affects the morphology of the MIL-125 changing from thick to thin nanotablets, but also greatly enhances the electrochemical performance of the V_xTiO₂@C. When used as an anode for SIBs, the V_0.1TiO₂@C exhibits a much higher reversible capacity of 211 mAh/g than that for the undoped TiO₂@C (only 156 mAh/g) after 150 cycles at 100 mA/g. Even after high-rate long-term cycling, the V_0.1TiO₂@C can still display a capacity of 180 mAh/g with a high capacity retention of 137% at 1000 mA/g after 4500 cycles. Structural/electrochemical measurements reveal that V-doping induces the formation of oxygen vacancies as well as Ti³⁺ species, which efficiently improve the electric conductivity and the ion diffusivity of the electrode. Meanwhile, the thinner V_0.1TiO₂@C nanotablets with porous structure and carbon hybridization could facilitate the ion/electron transfer with shortened diffusion pathways.

Crosslinking Nanoarchitectonics of Nitrogen-doped Carbon/MoS2 Nanosheets/Ti3 C2 Tx MXene Hybrids for Highly Reversible Sodium Storage

Although it is a promising sodium storage material due to its excellent electrochemical activity, small bandgap, and large interlayer spacing, layered molybdenum disulfide (MoS₂ ) suffers from poor rate capability and degraded cycling life, resulting from its serious aggregation upon preparation, sluggish reaction kinetics, and structure expansion during cycling. To address these issues, a polyethyleneimine (PEI)-assisted fabrication approach was developed for the rational synthesis of an interconnected framework with nitrogen-doped carbon-confined MoS₂ nanosheets/Ti₃ C₂ T_x MXene (MoS₂ /Ti₃ C₂ T_x @NC), where the PEI could guide the uniform growth of MoS₂ on Ti₃ C₂ T_x and the self-generated NC simultaneously enhanced its synergistic coupling with MoS₂ /Ti₃ C₂ T_x , thus contributing to the improvement of charge transfer, diffusion kinetics, and structural integrity of the hybrid electrode. Consequently, the desired MoS₂ /Ti₃ C₂ T_x @NC delivered impressive sodium storage performance, demonstrating high reversible capacities of 397.3 and 206.8 mAh g^-1 at 0.1 A g^-1 after 100 cycles and 0.5 A g^-1 after 500 cycles, respectively. Moreover, electrochemical kinetics analysis and charge storage mechanism manifested that high capacitive contribution, facilitated Na⁺ transport pathways, and synergistic electronic coupling between MoS₂ /Ti₃ C₂ T_x and NC contributed to the superior sodium storage performance.

Process optimization to enhance utilization efficiency of precipitants for chloride removal from flue gas desulfurization wastewater via Friedel's salt precipitation

The treatment cost for Cl^- removal by Friedel's salt precipitation depended significantly on utilization rate of the precipitant aluminate. In this study, effects of Ca/Al molar ratio, reaction time, temperature and Al/Cl molar ratio were investigated to maximize Al utilization rate for Cl^- removal from flue gas desulfurization wastewater. Batch results showed that the maximum Al utilization rate of 55.8-60.3% was obtained at Ca/Al ratio of 3.00, reaction time of 90 min, temperature of 35 °C and Al/Cl ratio of 0.50 regardless of the initial Cl^- concentration. The precipitate obtained at the highest Al utilization rate had the highest interlayer spacing, the best crystal integrity, and the strongest binding energy of the Al-OH bond. The optimized condition made ion exchange between Cl^- and OH^- easier, and obtained more stable Friedel's salt structure to adsorb Cl^-. Pilot-scale results showed that maximizing Al utilization rate with low dosages of precipitants had insignificant effects on the removal of Mg²⁺, Ca²⁺ and sulfate compared to the strategy to maximize Cl^-, but enhanced Al utilization rate from 38.2% to 56.4%. Economic analysis showed that enhancing Al utilization rate greatly reduced treatment cost of the Friedel's salt precipitation method by 30.5%, and made the two-stage desalination process more feasible and worth popularizing.

Oxygen-vacancy abundant alpha bismuth oxide with enhanced cycle stability for high-energy hybrid supercapacitor electrodes

Bi₂O₃ is an outstanding electrode material due to its high theoretical specific capacity. Hence, the synthesis of δ-Bi₂O₃ materials with high oxygen-vacancy contents could improve their electrochemical performances but causes easy conversion to α-Bi₂O₃ with low oxygen-vacancy contents, leading to poor cycling stability and limited practical applications. To overcome these problems, an effective strategy for constructing high oxygen vacancies α-Bi₂O₃ on activated carbon fiber paper (ACFP) is developed in this study. To this end, ACFP/Bi(OH)₃ is first synthesized by the solvothermal method and then converted to ACFP/α-Bi₂O₃ by in situ electrochemical activation. The proposed innovative electrochemical method quickly and easily introduces oxygen vacancies while preserving the three-dimensional structure, thereby promoting the charge transfer and ions diffusion in ACFP/α-Bi₂O₃. Consequently, the specific capacity of ACFP/α-Bi₂O₃ reaches 906C g^-1 at 1 A g^-1, and the capacity retention remains above 70% after 3000 cycles, a value higher than that of δ-Bi₂O₃ (45%). Furthermore, the hybrid supercapacitor device assembled by ACFP/α-Bi₂O₃ delivers a maximum energy density of 114.9 Wh kg^-1 at 900 W kg^-1 and outstanding cycle stability with 73.56 % retention after 5500 cycles. In sum, the proposed ACFP/α-Bi₂O₃ with high performance and good stability looks promising for use as bismuth-based anode materials in supercapacitors and aqueous batteries.

Interconnected MoS2 on 2D Graphdiyne for Reversible Sodium Storage

In this study, graphdiyne (GDY) was first reported as a substrate material for sodium-ion batteries (SIBs). The creative hybridization of GDY and molybdenum disulfide (MoS₂) endows the composite with unique heterostructural and morphological advantages that boost the charge transport rate and enhance the battery discharge properties. Electrochemical results indicated that the MoS₂@GDY anode displays a considerable discharge capacity of up to 328 mAh g^-1 at 1000 mA g^-1. A capacity retention of 93% even at testing current back to 200 mA g^-1 suggests superior rate characteristics. An outstanding stable cyclic performance of 217 mAh g^-1 is obtained at a high testing density. The attractive results not only demonstrate that GDY could be used not only as an effective conductive substrate to prevent the host material from agglomerating in the electrochemical process but also provide a novel design for fabricating efficient electrode materials for future energy-storage systems.

Rational Design of Embedded CoTe2 Nanoparticles in Freestanding N-Doped Multichannel Carbon Fibers for Sodium-Ion Batteries with Ultralong Cycle Lifespan

Although sodium-ion batteries (SIBs) have high potential for applications in large-scale energy storage, their limited cycle life and unsatisfactory energy density hinder their commercial applications. Here, a superior stable CoTe₂/carbon anode, in which CoTe₂ nanoparticles are embedded in freestanding N-doped multichannel carbon fiber (CoTe₂@NMCNFs), with ultralong cycle life for SIBs, is reported. Specifically, CoTe₂ nanoparticles are uniformly dispersed in the carbon matrix to inhibit its volume expansion and agglomeration during the desodiation/sodiation process, enabling a high-capacity and stable energy storage (retains 204.3 mAh g^-1/612.9 mAh cm^-3 at 1 A g^-1 after 2000 cycles with an ultralow capacity decay of 0.016% per cycle). Moreover, a CoTe₂@NMCNFs electrode exhibits a pseudocapacitive-dominated behavior, enabling the high-rate performance (152.4 mAh g^-1/457.2 mAh cm^-3 at 10 A g^-1). The battery-capacitive dual-model reaction mechanism and outstanding reversibility of the CoTe₂@NMCNFs composite are systematically investigated by ex situ XRD/SEM/TEM and a galvanostatic intermittent titration technique test, as well as surface capacitance calculations. More importantly, the fabricated sodium-ion CoTe₂@NMCNFs//P2-NaNMMT-4 full cell delivers a stable reversible capacity of 445 Wh kg^-1_anode at 0.2 A g^-1 and an excellent rate performance. The facile synthetic approach together with unique nanostructural design, provides a meaningful reference for the rational design of next-generation ultralong cycle-life SIBs anodes.

WS2 nanosheets@ZIF-67-derived N-doped carbon composite as sodium ion battery anode with superior rate capability

Devising novel composite electrodes with particular structural/electrochemical characteristics becomes an efficient strategy to advance the performance of rechargeable battery. Herein, considering the homogeneous transition metal sulfide with N-doped carbon derived from zeolitic imidazolate framework-67 (ZIF-67) and WS₂ with large interlayer spacing, a laurel-leaf-like Co₉S₈/WS₂@N-doped carbon bimetallic sulfide (Co₉S₈/WS₂@NC) is engineered and prepared via a step-by-step method. As an electrode material for sodium ion batteries (SIBs), Co₉S₈/WS₂@NC composite delivers high capacities of 480 and 405 mA h g^-1 at 0.1 and 1.0 A g^-1, respectively. As the current density increases from 0.1 to 5.0 A g^-1, it provides specific capacity of 359 mA h g^-1 with a capacity retention rate of 78.0%, which is higher than that of Co₉S₈@NC (63.5%) and WS₂ (58.6%). The Co₉S₈/WS₂@NC composite anode maintains a stable specific capacity (354 mA h g^-1 at 2.0 A g^-1). It also exhibits a high capacitive contribution ratio of 90.8% at 1.0 mV s^-1. This study provides a new and reliable insight for designing bimetallic sulfide with two-dimensional nanostructure for energy storage.

Hierarchical WSe2 nanoflower as a cathode material for rechargeable Mg-ion batteries

Transition metal dichalcogenides (TMDs) have emerged as a promising material in the energy field due to their unique structural arrangement. In this work, ordered flower-like WSe₂ nanosheet was synthesized through simple one-step hydrothermal method, and its cathode application for rechargeable Mg-ion batteries was assessed. The WSe₂ cathode exhibits a high reversible capacity above 265 mAh g^-1 at 50 mA g^-1, excellent cycling life of 90% initial capacitance that can be ceaselessly harvested for 100 cycles at 50 mA g^-1, and superior rate capability of 70% initial capacitance maintained even at the current density of 500 mA g^-1. This work paves the way for the application of WSe₂ cathode in Mg-ion and other rechargeable batteries.

Orientated VSe2 nanoparticles anchored on N-doped hollow carbon sphere for high-stable aqueous energy application

Transition metal dichalcogenides (TMDs) have been considered as the promising energy storage materials due to their unique crystalline structure. In this work, the VSe₂ nanoparticles are vertically anchored on N-doping carbon (NC) hollow nanosphere (VSe₂@NC) for aqueous energy application. The electrochemical measurements indicate that the VSe₂@NC electrode exhibits outstanding electrochemical properties with high specific capacitance and excellent cycling life. Moreover, the asymmetric supercapacitor was assembled by using VSe₂@NC cathode and activated carbon anode. It shows high energy density of 85.41 Wh Kg^-1 at a power density of 701.99 W Kg^-1, and high-stable cycling performance of 90% retention after 2000 cycles. The superior properties are attributed to the particular hollow structure design, which accommodates both the high specific capacity of VSe₂ and the desired electrical conductivity of N-doping carbon sphere template.