Metal-Semiconductor Phase Twinned Hierarchical MoS2 Nanowires with Expanded Interlayers for Sodium-Ion Batteries with Ultralong Cycle Life

Few-layer MoS2 promotes SnO2@C nano-composites for high performance sodium ion batteries

Due to its abundance, high theoretical capacity, and environmental benefits, tin dioxide (SnO2) shows great potential as an anode material in sodium-ion batteries (SIBs). However, the inadequate electrical conductivity and significant volume fluctuations during the Na+ insertion/extraction process are major limitations to its practical application. Herein, few-layered MoS2@SnO2@C (FMSC) composites with hierarchical nanostructures were prepared through a two-step hydrothermal method. As expected, the electrochemical tests show that the FMSC exhibits superior electrochemical properties, such as an outstanding rate capability of 288.9 mA h g-1 at a current density of 2 A g-1, a high reversible capacity of 415.9 mA h g-1 after 50 cycles at a current density of 0.1 A g-1, and remarkable cycling stability of 158.4 mA h g-1 after 4400 cycles at a current density of 5 A g-1, as an anode material for SIBs. The exceptional performance can be attributed to the presence of a thin layer of MoS2, which enhances surface electrochemical reactions and provides a flexible structure.

Synthesis and Electrocatalytic Applications of Layer-Structured Metal Chalcogenides Composites

Featured with the attractive properties such as large surface area, unique atomic layer thickness, excellent electronic conductivity, and superior catalytic activity, layered metal chalcogenides (LMCs) have received considerable research attention in electrocatalytic applications. In this review, the approaches developed to synthesize LMCs-based electrocatalysts are summarized. Recent progress in LMCs-based composites for electrochemical energy conversion applications including oxygen reduction reaction, carbon dioxide reduction reaction, oxygen evolution reaction, hydrogen evolution reaction, overall water splitting, and nitrogen reduction reaction is reviewed, and the potential opportunities and practical obstacles for the development of LMCs-based composites as high-performing active substances for electrocatalytic applications are also discussed. This review may provide an inspiring guidance for developing high-performance LMCs for electrochemical energy conversion applications.

Electron Configuration Modulation Induced Stabilized 1T-MoS2 for Enhanced Sodium Ion Storage

1T-MoS2 has become an ideal anode for sodium-ion batteries (SIBs). However, the metastable feature of 1T-MoS2 makes it difficult to directly synthesize under normal conditions. In addition, it easily transforms into 2H phase via restacking, resulting in inferior electrochemical performance. Herein, the electron configuration of Mo 4d orbitals is modulated and the stable 1T-MoS2 is constructed by nickel (Ni) introduction (1T-Ni-MoS2). The original electron configuration of Mo 4d orbitals is changed via the electron injection by Ni, which triggers the phase transition from 2H to 1T phase, thus improving the electrical conductivity and accelerating the redox kinetics of the material. Consequently, 1T-Ni-MoS2 exhibits superior rate capability (266.8 mAh g-1 at 10 A g-1) and excellent cycle life (358.7 mAh g-1 at 1 A g-1 after 350 cycles). In addition, the assembled Na3V2(PO4)3/C||1T-Ni-MoS2 full cells deliver excellent electrochemical properties and show great prospects in energy storage devices.

Molecular modulation strategies for two-dimensional transition metal dichalcogenide-based high-performance electrodes for metal-ion batteries

In the past few decades, great efforts have been made to develop advanced transition metal dichalcogenide (TMD) materials as metal-ion battery electrodes. However, due to existing conversion reactions, they still suffer from structural aggregation and restacking, unsatisfactory cycling reversibility, and limited ion storage dynamics during electrochemical cycling. To address these issues, extensive research has focused on molecular modulation strategies to optimize the physical and chemical properties of TMDs, including phase engineering, defect engineering, interlayer spacing expansion, heteroatom doping, alloy engineering, and bond modulation. A timely summary of these strategies can help deepen the understanding of their basic mechanisms and serve as a reference for future research. This review provides a comprehensive summary of recent advances in molecular modulation strategies for TMDs. A series of challenges and opportunities in the research field are also outlined. The basic mechanisms of different modulation strategies and their specific influences on the electrochemical performance of TMDs are highlighted.

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.

Covalently bridged bond assembly of MoS2lamellae onto a graphene sheet: an outstanding electrode for high rate and long-life lithium/sodium-ion batteries

The practical application of Molybdenum sulphide (MoS2) electrodes has been hindered by its structural instability, and poor electrical conductivity. To enhance the cycle stability and rate performance of MoS2in lithium/sodium-ion batteries (LIBs/SIBs), we synthesized a graphene-supported MoS2composite (MoS2@rGO) with affluent covalent bridged bonds through a facile and scalable hydrothermal and annealing process. The covalent bridged bonds of Mo-S-C, Mo-O-C and C-O-S provide an effective charge transfer path between MoS2and graphene, facilitating fast charge hopping and improving rate performance. As anode materials for LIBs, the MoS2@rGO exhibited exceptional long-term cycle life (906 mAh g-1at 1.0 A g-1after 400 cycles) and outstanding rate capability (1267.7/314.7 mAh g-1at 0.1/6.5 A g-1). Additionally, the MoS2@rGO electrode demonstrated a stable reversible capacity of 521.7 mAh g-1at 1.0 A g-1after 700 cycles and excellent rate capabilities of 665.1 and 326.3 mAh g-1at 0.1 and 10.0 A g-1in SIBs. The edge Mo of MoS2is directly coupled with the oxygen of the functional group on rGO, achieved by adjusting the pH value of the solution to tune the surface charge feature, can effectively enhance the structural stability of electrode even under higher current density.

Metal-Organic Assembly Strategy for the Synthesis of Layered Metal Chalcogenide Anodes for Na+ /K+ -Ion Batteries

Layered transition metal chalcogenides (MX, M=Mo, W, Sn, V; X=S, Se, Te) have large ion transport channels and high specific capacity, making them promising for large-sized Na⁺ /K⁺ energy-storage technologies. Nevertheless, slow reaction kinetics and huge volume expansion will induce an undesirable electrochemical performance. Numerous efforts have been devoted to designing MX anodes and enhancing their electrochemical performance. Based on the metal-organic assembly strategy, nanostructural engineering, combination with carbon materials, and component regulation can be easily realized, which effectively boost the performance of MX anodes. In this Review, we present a comprehensive overview on the synthesis of MX nanostructure using the metal-organic assembly strategy, which can realize the design of MX nanostructures, based on self-sacrificial templates, host@guest tailored templates, post-modified layer and derivative templates. The preparation routes and structure evolution are mainly discussed. Then, Mo-, W-, Sn-, V-based chalcogenides used for Na⁺ /K⁺ energy storage are reviewed, and the relationship between the structure and the electrochemical performance, as well as the energy storage mechanism are emphasized. In addition, existing challenges and future perspectives are also presented.

Molecular engineering on a MoS2 interlayer for high-capacity and rapid-charging aqueous ion batteries

Rechargeable aqueous ion batteries (AIBs) play essential roles in the increasing demand for high-performance energy storage systems, and yet they are hampered by the lack of suitable cathode materials because of the sluggish intercalation kinetics. In this work, we develop an effective and feasible strategy to enhance the performance of AIBs by broadening the interlayer spacing by using intercalated CO₂ molecules to promote the intercalation kinetics by using first principles simulations. Compared with pristine MoS₂, the intercalation of CO₂ molecules with a 3/4 ML coverage significantly increases the interlayer spacing to 9.383 Å from 6.369 Å and the diffusivity is boosted by 12 orders of magnitude for Zn ions, 13 orders for Mg ions and one order for Li ions. Moreover, the concentrations of intercalating Zn, Mg and Li ions are enhanced by 7, 1 and 5 orders of magnitude, respectively. The significantly increased diffusivity and intercalation concentration of metal ions signify that intercalating CO₂ bilayer MoS₂ is a promising cathode material to realize metal ion batteries with a rapid charging capability and high storage capacity. The strategy developed in this work can be generally applied to increase the metal ion storage capacity in transition metal dichalcogenide (TMD)- and other layered material-based cathodes and make them promising for next-generation rapidly rechargeable batteries.

Evolution of Stabilized 1T-MoS2 by Atomic-Interface Engineering of 2H-MoS2 /Fe-Nx towards Enhanced Sodium Ion Storage

Metallic conductive 1T phase molybdenum sulfide (MoS₂ ) has been identified as promising anode for sodium ion (Na⁺ ) batteries, but its metastable feature makes it difficult to obtain and its restacking during the charge/discharge processing result in part capacity reversibility. Herein, a synergetic effect of atomic-interface engineering is employed for constructing 2H-MoS₂ layers assembled on single atomically dispersed Fe-N-C (SA Fe-N-C) anode material that boosts its reversible capacity. The work-function-driven-electron transfer occurs from SA Fe-N-C to 2H-MoS₂ via the Fe-S bonds, which enhances the adsorption of Na⁺ by 2H-MoS₂ , and lays the foundation for the sodiation process. A phase transfer from 2H to 1T/2H MoS₂ with the ferromagnetic spin-polarization of SA Fe-N-C occurs during the sodiation/desodiation process, which significantly enhances the Na⁺ storage kinetics, and thus the 1T/2H MoS₂ /SA Fe-N-C display a high electronic conductivity and a fast Na⁺ diffusion rate.

Electrochemically Controllable Synthesis of Low-Valence Titanium Sulfides for Advanced Sodium Ion Batteries with Ultralong Cycle Life in a Wide Potential Window

Low-valence titanium sulfides (LVTS) have metal-like electrical conductivities and a strong polysulfide binding abilities, which are promising anodes for sodium ion batteries with high capacities and long cycle lifes. However, it is difficult for traditional synthesis methods to synthesize LVTS without impurities. The electric field regulation method possesses the advantages of flexibility and high efficiency, achieving accurate control of the metal reduction process by adjusting the electrolysis potential and reaction time. In this work, we synthesized a series of LVTS (TiS and Ti₂S) using electric field control methods and investigated their electrochemical behaviors as sodium storage anodes for the first time. Compared with traditional TiS₂, LVTS display remarkable Na storage properties under the condition of complete electrochemical conversion at 0.005-3 V. Especially for TiS, it demonstrates a high capacity of 409 mAh g^-1 at 1 A g^-1 and inspiring cyclic stability over 6000 cycles. The large number of vacancies in the crystal structure can chemically anchor polysulfides and alleviate their dissolution in the electrolyte, resulting in superior long-term cyclic stability. The high intrinsic conductivity of LVTS is in favor of rapid transfer of electrons and promotes the fast conversion of polysulfides to sodium sulfides, thus realizing high reversible capacities. Moreover, with its fast Na⁺ transport kinetics, the as-prepared TiS demonstrates an impressive rate performance of 321 mAh g^-1 at 15 A g^-1. Overall, the electric field regulation method is flexible and efficient, which provides a new route for the preparation of high-performance electrode materials. Moreover, nonstoichiometric metal compounds possess abundant active sites and rapid electron transport kinetics, which provide a new choice for promising sodium storage materials in large-scale energy storage applications.

Molybdenum Oxynitride Atomic Nanoclusters Bonded in Nanosheets of N-Doped Carbon Hierarchical Microspheres for Efficient Sodium Storage

Transition metal nitrides have attracted considerable attention as great potential anode materials due to their excellent metallic conductivity and high theoretical specific capacity. However, their cycling performance is impeded by their instability caused by the reaction mechanism. Herein, we report the engineering and synthesis of a novel hybrid architecture composed of MoO_2.0N_0.5 atomic nanoclusters bonded in nanosheets of N-doped carbon hierarchical hollow microspheres (MoO_2.0N_0.5/NC) as an anode material for sodium-ion batteries. The facile self-templating strategy for the synthesis of MoO_2.0N_0.5/NC involves chemical polymerization and subsequent one-step calcination treatments. The design is beneficial to improve the electrochemical kinetics, buffer the volume variation of electrodes during cycling, and provide more interfacial active sites for sodium uptake. Due to these unique structural and compositional merits, these MoO_2.0N_0.5/NC exhibits excellent sodium storage performance in terms of superior rate capability and stable long cycle life. The work shows a feasible and effective way to design novel host candidates and solve the long-term cycling stability issues for sodium-ion batteries.

In-situ fabrication of active interfaces towards FeSe as advanced performance anode for sodium-ion batteries

Transition metal selenides have gained enormous interest as anodes for sodium ion batteries (SIBs). Nonetheless, their large volume expansion causing poor rate and inferior cycle stability during Na⁺ insertion/extraction process hinders their further applications in SIBs. Herein, a confined-regulated interfacial engineering strategy towards the synthesis of FeSe microparticles coated by ultrathin nitrogen-doped carbon (NC) is demonstrated (FeSe@NC). The strong interfacial interaction between FeSeand NC endows FeSe@NC with fast electron/Na⁺ transport kinetics and outstanding structural stability, delivering unexceptionable rate capability (364 mAh/gat 10 A/g) and preeminent cycling durability (capacity retention of 100 % at 1 A/g over 1000 cycles). Furthermore, variousex situcharacterization techniques and density functional theory (DFT) calculations have been applied to demonstrate the Na⁺ storage mechanism of FeSe@NC. The assembled Na₃V₂(PO₄)₂F₃@rGO//FeSe@NC full cell also displays a high capacity of 241 mAh/gat 1 A/g with the capacity retention of nearly 100 % over 2000 cycles, and delivers a supreme energy density of 135 Wh kg^-1 and a topmost power density of 495 W kg^-1, manifesting the latent applications of FeSe@NC in the fast charging SIBs.

Integrating Bi@C Nanospheres in Porous Hard Carbon Frameworks for Ultrafast Sodium Storage

Sodium-ion batteries (SIBs) have emerged as an alternative technology because of their merits in abundance and cost. Realizing their real applications, however, remains a formidable challenge. One is that among the limitations of anode materials, the alloy-type candidates tolerate fast capacity fading during cycling. Here, a 3D framework superstructure assembled with carbon nanobelt arrays decorated with a metallic bismuth (Bi) nanospheres coated carbon layer by thermolysis of Bi-based metal-organic framework nanorods is synthesized as an anode material for SIBs. Due to the unique structural superiority, the anode design promotes excellent sodium-storage performance in terms of high capacity, excellent cycling stability, and ultrahigh rate capability up to 80 A g^-1 with a capacity of 308.8 mAh g^-1 . The unprecedented sodium-storage ability is not only attributed to the unique hybrid architecture, but also to the production of a homogeneous and thin solid electrolyte interface layer and the formation of uniform porous nanostructures during cycling in the ether-based electrolyte. Importantly, deeper understanding of the underlying cause of the performance improvement is illuminated, which is vital to provide the theoretical basis for application of SIBs.

Superstructured Nanocrystals/Dual-Doped Mesoporous Carbon Anodes for High-Performance Sodium-Ion Batteries

Two-dimensional ordered superstructures have been attracting considerable attention due to their interesting properties and potential applications. However, designing ideal functional superstructures with excellent electrochemical properties is still a major challenge, and an in-depth understanding of the structure-activity relationship of electrodes remains to be achieved. To elucidate this critical issue, herein, we rationally designed and synthesized for the first time superstructured TiO₂/dual-doped mesoporous carbon anodes using confined space and surface coassembly strategies. Our method primarily relied on the larger interlayer space few-layered MXene and its negatively charged surface, allowing hexamethylenetetramine intercalation and surface electrostatic adsorption. The superstructured TiO₂/dual-doped mesoporous carbon was successfully assembled by the thermal decomposition of a confined carbon precursor. Subsequently, the comparison of Na⁺-storage properties of various anodes was carried out based on the results of structural characterization techniques and electrochemical analysis methods. The results showed that the optimized anode (N/O-C@TiO₂-20) can deliver a reversible capacity of 165 mA h g^-1 after 1000 cycles at a current density of 1 A g^-1, indicating excellent electrochemical properties. The enhancement can be attributed to the synergistic effect of carbon domains, defective nanocrystals, and a covalently coupled interface between TiO₂ and mesoporous carbon. Our work not only offered a new strategy for the assembly and regulation of superstructures to promote the electrochemical performance but also enlightened the rational design of advanced anodes for sodium-ion battery application.

Ultrathin-Walled Bi2 S3 Nanoroll/MXene Composite toward High Capacity and Fast Lithium Storage

It is extremely important to develop a high energy density power source with rapid charge-discharge rate to meet people's growing needs. Hence, the development of advanced electrode materials is the top priority. Herein, a simple yet elaborate vacuum-assisted room-temperature phase transfer method is reported to transform MXene nanosheets from water into organic solution. Subsequently, an in-situ growth strategy is employed to deposit ultrathin-walled bismuth sulfide (Bi₂ S₃ ) nanorolls on MXene surface to prepare Bi₂ S₃ /MXene composite as an efficient and high-performance anode material for lithium-ion batteries. Attributed to the unique nanoroll-like structure and the strong synergistic effect, the Bi₂ S₃ /MXene-10 composite can deliver the high discharge capacities of 849 and 541 mAh g^-1 at 0.1 and 5 A g^-1 , respectively. The Bi₂ S₃ /MXene-10 electrode can deliver a high specific capacity of 541 mAh g^-1 even after 600 cycles at a large current density of 1 A g^-1 , proving the superb cycling stability of the Bi₂ S₃ /MXene-10 composite. Additionally, the simple vacuum-assisted room-temperature phase transfer strategy can enlighten researchers to expand the potential application of MXene. Furthermore, the formation mechanism of Bi₂ S₃ nanorolls is also proposed, which may open a new avenue to design and fabricate other nanoroll-like structures.

The Multicomponent Synergistic Effect of Sandwich Structure Hierarchical Nanofibers for Enhanced Sodium Storage

Constructing hierarchical micro/nanostructures as anodes for sodium ion batteries is an important approach for exploiting efficient energy storage devices. Herein, sandwich structure hierarchical nanofibers composed of hollow carbon fibers as the substrate, and MoS₂ as the interlayer with Co and/or ZnS nanoparticles anchoring in carbon skeletons as the outer shell (carbon nanofiber/MoS₂ /Co-ZnS⊂NC) are prepared via a multistep reaction strategy. Profiting from the unique hierarchical structure, abundant migration channels of Na⁺ , and multicomponent synergistic effects, the rapid diffusion kinetics are ensured and the utilization of active materials is maximized. The coaxial structure can evenly disperse volumetric strain, making structural stability guaranteed. Hierarchical nanofibers deliver a high reversible capacity of 352.3 mAh g^-1 at 5.0 A g^-1 over 3000 cycles. A discharge capacity of 182.5 mAh g^-1 is retained even after 10 000 cycles at 10.0 A g^-1 as well as a high rate capacity of 202.0 mAh g^-1 up to 30 A g^-1 . The optimal atomic ratio of Co element is further verified by the kinetic analysis. The full-cells assembled with Na₃ V₂ (PO₄ )₃ cathode provide a high capacity of 179.2 mAh g^-1 at 1.0 A g^-1 for 500 cycles. Combining in situ and ex situ characterizations and theoretical calculations, possible sodium storage mechanisms and the origin of superior electrochemical properties are revealed.

Construction of 1T@2H MoS2 heterostructures in situ from natural molybdenite with enhanced electrochemical performance for lithium-ion batteries

Natural molybdenite, an inexpensive and naturally abundant material, can be directly used as an anode material for lithium-ion batteries. However, how to release the intrinsic capacity of natural molybdenite to achieve high rate performance and high capacity is still a challenge. Herein, we introduce an innovative, effective, and one-step approach to preparing a type of heterostructure material containing 1T@2H MoS2 crafted from insertion and expansion of natural molybdenite. The metallic 1T phase formed in situ can significantly improve the electronic conductivity of MoS2. At the same time, 1T@2H MoS2 heterostructures can provide an internal electric field (E-field) to accelerate the migration rate of electrons and ions, promote the charge transfer behaviour, and ensure the reaction reversibility and lithium storage kinetics. Such worm-like 1T@2H MoS2 heterostructures also have a large specific surface area and a large number of defects, which will help shorten the lithium-ion transmission distance and provide more ion transmission channels. As a result, it exhibits a discharge capacity of 788 mA h g-1 remarkably at 100 mA g-1 after 485 cycles and stable cycling performance. It also shows excellent magnification performance of 727 mA h g-1 at 1 A g-1, compared to molybdenite concentrate. Briefly, this work's heterostructure architectures open up a new avenue for applying natural molybdenite in lithium-ion batteries, which has the potential to achieve large-scale commercial applications.

Controllable Synthesis of Novel Orderly Layered VMoS2 Anode Materials with Super Electrochemical Performance for Sodium-Ion Batteries

Sodium-ion batteries (SIBs), being an attractive candidate of lithium-ion batteries, have attracted widespread attention as a result of sufficient sodium resource with low price and their comparable suitability in the field of energy storage. However, one of the main challenges for their wide-scale application is to develop suitable anode materials with excellent electrochemical performance. Herein, a novel orderly layered VMoS₂ (OL-VMS) anode material was synthesized through a facile hydrothermal self-assembly approach followed by a heating procedure. As the anode material of the SIBs, the unique structure of OL-VMS not only facilitated the rapid migration of sodium ions between the stacked layers but also provided a stable framework for the volume change in the process of intercalation/deintercalation. In addition, vanadium mediating in the framework caused more defects to produce abundant storage sites for Na⁺. As such, the obtained OL-VMS-based anode exhibited high reversible capacities of 602.9 mAh g^-1 at 0.2 mA g^-1 and 534 mAh g^-1 even after 190-cycle operation at 2 A g^-1. Furthermore, the OL-VMS-based anode delivered an outstanding specific capacity of 626.4 mAh g^-1 after 100-cycle testing at 2 A g^-1 in a voltage range from 0.01 to 3 V. In particular, even in the absence of conductive carbon, it still showed an excellent specific capacity of 260 mAh g^-1 at 1 A g^-1 after 130 cycles in a 0.3-3 V voltage range, which should contribute to the cost reduction and energy density increase.

Electron-Injection-Engineering Induced Phase Transition toward Stabilized 1T-MoS2 with Extraordinary Sodium Storage Performance

Phase transition engineering, with the ability to alter the electronic structure and physicochemical properties of materials, has been widely used to achieve the thermodynamically unstable metallic phase MoS₂ (1T-MoS₂), although the complex operating conditions and low yield of previous strategies make the large-scale fabrication of 1T-MoS₂ a big challenge. Herein, we report a facile electron injection strategy for phase transition engineering and fabricate a composite of conductive TiO chemically bonded to 1T-MoS₂ nanoflowers (TiO-1T-MoS₂ NFs) on a large scale. The underlying mechanism analysis reveals that electron-injection-engineering triggers a reorganization of the Mo 4d orbitals and results in a 100% phase transition of MoS₂ from 2H to 1T. In the TiO-1T-MoS₂ NFs composite, the 1T-MoS₂ demonstrates a higher electronic conductivity, a lower Na⁺ diffusion barrier, and a more restricted S release than 2H-MoS₂. In addition, conductive TiO bonding successfully resolves the stability challenge of the 1T phase. These merits endow TiO-1T-MoS₂ NFs electrodes with an excellent rate capability (650/288 mAh g^-1 at 50/20 000 mA g^-1, respectively) and an outstanding cyclability (501 mAh g^-1 at 1000 mA g^-1 after 700 cycles) in sodium ion batteries. Such an improvement signifies that this facile and scalable phase-transition engineering combined with a deep mechanism analysis offers an important reference for designing advanced materials for various applications.

A Series of Molecule-Intercalated MoS2 as Anode Materials for Sodium Ion Batteries

Molybdenum disulfide (MoS₂) with a graphite-like layer structure has attracted substantial interest as an anode material for sodium ion batteries (SIBs), but its inherent poor electrical conductivity and slow sodium ion transportation are the two important factors that limit its use in SIBs. Here, we report a general approach to synthesize a series of molecule-intercalated MoS₂ with a precisely controlled interlayer distance of 0.62 to 1.24 nm in which the electrical conductivity could be also widely and finely adjusted from 1.3 × 10^-4 to 3.5 × 10^-2 S cm^-1 via the insertion of different molecules. By adjusting the interlayer space and enhancing the electrical conductivity, the highest initial sodium ion storage capacity of 465 mA h g^-1 (vs 195 mA h g^-1 for the pure MoS₂ anode) and the highest capacity of 420 mA h g^-1 (vs 31 mA h g^-1 for the pure MoS₂ anode) after 600 cycles at a rate of 100 mA g^-1 were obtained. The excellent performance is credited to the rapid Na⁺ and electron transport and higher material utilization derived from the synergistic effect of the expanded interlayer space and the higher electronic conductivity. The results provide some inspiration for the design and construction of superior layered anode materials for sodium-ion batteries.

MoS2 encapsulated in three-dimensional hollow carbon frameworks for stable anode of sodium ion batteries

MoS₂ wrapped in nitrogen-doped three-dimensional hollow carbon frameworks is designed for improved sodium ion battery anode performance.

Rational Design of Sb@C@TiO2 Triple-Shell Nanoboxes for High-Performance Sodium-Ion Batteries

Antimony is an attractive anode material for sodium-ion batteries (SIBs) owing to its high theoretical capacity and appropriate sodiation potential. However, its practical application is severely impeded by its poor cycling stability caused by dramatic volumetric variations during sodium uptake and release processes. Here, to circumvent this obstacle, Sb@C@TiO₂ triple-shell nanoboxes (TSNBs) are synthesized through a template-engaged galvanic replacement approach. The TSNB structure consists of an inner Sb hollow nanobox protected by a conductive carbon middle shell and a TiO₂ -nanosheet-constructed outer shell. This structure offers dual protection to the inner Sb and enough room to accommodate volume expansion, thus promoting the structural integrity of the electrode and the formation of a stable solid-electrolyte interface film. Benefiting from the rational structural design and synergistic effects of Sb, carbon, and TiO₂ , the Sb@C@TiO₂ electrode exhibits superior rate performance (212 mAh g^-1 at 10 A g^-1 ) and outstanding long-term cycling stability (193 mAh g^-1 at 1 A g^-1 after 4000 cycles). Moreover, a full cell assembled with a configuration of Sb@C@TiO₂ //Na₃ (VOPO₄ )₂ F displays a high output voltage of 2.8 V and a high energy density of 179 Wh kg^-1 , revealing the great promise of Sb@C@TiO₂ TSNBs as the electrode in SIBs.

Anchoring SnS2 on TiC/C Backbone to Promote Sodium Ion Storage by Phosphate Ion Doping

Tin disulfide (SnS₂ ) shows promising properties toward sodium ion storage with high capacity, but its cycle life and high rate capability are still undermined as a result of poor reaction kinetics and unstable structure. In this work, phosphate ion (PO₄ ^3- )-doped SnS₂ (P-SnS₂ ) nanoflake arrays on conductive TiC/C backbone are reported to form high-quality P-SnS₂ @TiC/C arrays via a hydrothermal-chemical vapor deposition method. By virtue of the synergistic effect between PO₄ ^3- doping and conductive network of TiC/C arrays, enhanced electronic conductivity and enlarged interlayer spacing are realized in the designed P-SnS₂ @TiC/C arrays. Moreover, the introduced PO₄ ^3- can result in favorable intercalation/deintercalation of Na⁺ and accelerate electrochemical reaction kinetics. Notably, lower bandgap and enhanced electronic conductivity owing to the introduction of PO₄ ^3- are demonstrated by density function theory calculations and UV-visible absorption spectra. In view of these positive factors above, the P-SnS₂ @TiC/C electrode delivers a high capacity of 1293.5 mAh g^-1 at 0.1 A g^-1 and exhibits good rate capability (476.7 mAh g^-1 at 5 A g^-1 ), much better than the SnS₂ @TiC/C counterpart. This work may trigger new enthusiasm on construction of advanced metal sulfide electrodes for application in rechargeable alkali ion batteries.

MnSe embedded in carbon nanofibers as advanced anode material for sodium ion batteries

MnSe with high theoretical capacity and reversibility is considered as a promising material for the anode of sodium ion batteries. In this study, MnSe nanoparticles embedded in 1D carbon nanofibers (MnSe-NC) are successfully prepared via facile electrospinning and subsequent selenization. A carbon framework can effectively protect MnSe dispersed in it from agglomeration and can accommodate volume variation in the conversion reaction between MnSe and Na⁺ to guarantee cycling stability. The 1D fiber structure can increase the area of contact between electrode and electrolyte to shorten the diffusion path of Na⁺ and facilitate its transfer. According to the kinetic analysis, the storage process of sodium by MnSe-NC is a surface pseudocapacitive-controlled process with promising rate capability. Impressively, An MnSe-NC anode in sodium ion full cells is investigated by pairing with an Na₃V₂(PO₄)₂@rGO cathode, which exhibits a reversible capacity of 195 mA h g^-1 at 0.1 A g^-1.

Hierarchical Octahedra Constructed by Cu2 S/MoS2 ⊂Carbon Framework with Enhanced Sodium Storage

Metal sulfides have aroused considerable attention for efficient sodium storage because of their high capacity and decent redox reversibility. However, the poor rate capability and fast capacity decay greatly hinder their practical application in sodium-ion batteries. Herein, a self-template-based strategy is designed to controllably synthesize hierarchical microoctahedra assembled with Cu₂ S/MoS₂ heterojunction nanosheets in the porous carbon framework (Cu₂ S/MoS₂ ⊂PCF) via a facile coprecipitation method coupled with vulcanization treatment. The Cu₂ S/MoS₂ ⊂PCF microoctahedra with 2D hybrid nanosubunits reasonably integrate several merits including facilitating the diffusion of electrons and Na⁺ ions, enhancing the electric conductivity, accelerating the ion and charge transfer, and buffering the volume variation. Therefore, the Cu₂ S/MoS₂ ⊂PCF composite manifests efficient sodium storage performance with high capacity, long cycling life, and excellent rate capability.

Porous CuO@C composite as high-performance anode materials for lithium-ion batteries

The in situ formation of a carbon matrix can confine the growth of CuO nanoparticles, which can provide more exposed active sites for electrochemical reactions.