Ultralong Sb2Se3 Nanowire-Based Free-Standing Membrane Anode for Lithium/Sodium Ion Batteries

First principles theoretical of designing sandwich-like metallic BP4monolayer as anode for alkali metal-ion batteries

Phosphorene has been widely used as anode material for batteries. However, the huge volume change during charging and discharging process, the semiconductor properties, and the high open circuit voltage limit its application. Based on this, by introducing the electron-deficient boron atoms into blue phosphorene, we proposed a P-rich sandwich-like BP4monolayer by density functional theory calculation and particle swarm optimization. The BP4monolayer shows good thermodynamic and dynamic stability, as well as chemical stability in O2atmosphere, mainly due to the strengthened P-P bond of the outer layer by the middle boron atoms adoptingsp3hybridization. According to the band structure, the BP4monolayer shows metallic property, which is beneficial to electron conductivity. Furthermore, compared with blue phosphorene and black phosphorene, the P-rich BP4monolayer shows higher theoretical capacity for Li, Na, and K of 1193.90, 1119.28, and 397.97 mA h g-1, respectively. The lattice constant of BP4monolayer increases only 3.73% (Li), 2.52% (Na) after Li/Na fully adsorbed on the anode. More importantly, the wettability of BP4monolayer in the electrolyte is comparable to that of graphene. These findings show that the stable sandwich-like BP4monolayer has potential as a lightweight anode material.

A metallic two-dimensional b-BS2 monolayer as a superior Na/K-ion battery anode

Two-dimensional (2D) materials with light weight and ultra-high electrical conductivity are expected to exhibit high capacity as anodes of batteries. We have explored the curved square lattice BS2 (b-BS2) monolayer possessing a space group similar to the transition metal chloride (space group: P4̄M2). The electrochemical performance of the b-BS2 monolayer as the anode for various metal-ion batteries (Li, Na, K, Mg, Ca, and Al) has been investigated. It exhibits low diffusion energy barrier, high theoretical capacity, and low open circuit voltage for Na/K-ion batteries (SIBs/PIBs). The ultrahigh energy densities of 2146.08 and 715.36 mA h g-1 can be achieved with the stoichiometries BS2Na6 and BS2K2, respectively. Furthermore, the b-BS2 monolayer may be synthesized on the surfaces of metal substrate materials (Ag(111), Al(111), and Au(111)). These results indicate that the b-BS2 monolayer is a good candidate for the anode material of SIBs/PIBs.

Metal Selenides Find Plenty of Space in Architecting Advanced Sodium/Potassium Ion Batteries

The rapid evolution of smart grid system urges researchers on exploiting systems with properties of high-energy, low-cost, and eco-friendly beyond lithium-ion batteries. Under the circumstances, sodium- and potassium-ion batteries with the semblable work mechanism to commercial lithium-ion batteries, hold the merits of cost-effective and earth-abundant. As a result, it is deemed a promising candidate for large-scale energy storage devices. Exploiting appropriate active electrode materials is in the center of the spotlight for the development of batteries. Metal selenides with special structures and relatively high theoretical capacity have aroused broad interest and achieved great achievements. To push the smooth development of metal selenides and enhancement of the electrochemical performance of sodium- and potassium-ion batteries, it is vital to grasp the inherent properties and electrochemical mechanisms of these materials. Herein, the state-of-the-art development and challenges of metal selenides are summarized and discussed. Meanwhile, the corresponding electrochemical mechanism and future development directions are also highlighted.

Scalable Synthesis of Selenide Solid-State Electrolytes for Sodium-Ion Batteries

Solid-state sodium-ion batteries employing superionic solid-state electrolytes (SSEs) offer low manufacturing costs and improved safety and are considered to be a promising alternative to current Li-ion batteries. Solid-state electrolytes must have high chemical/electrochemical stability and superior ionic conductivity. In this work, we employed precursor and solvent engineering to design scalable and cost-efficient solution routes to produce air-stable sodium selenoantimonate (Na3SbSe4). First, a simple metathesis route is demonstrated for the production of the Sb2Se3 precursor that is subsequently used to form ternary Na3SbSe4 through two different routes: alcohol-mediated redox and alkahest amine-thiol approaches. In the former, the electrolyte was successfully synthesized in EtOH by using a similar redox solution coupled with Sb2Se3, Se, and NaOH as a basic reagent. In the alkahest approach, an amine-thiol solvent mixture is utilized for the dissolution of elemental Se and Na and further reaction with the binary precursor to obtain Na3SbSe4. Both routes produced electrolytes with room temperature ionic conductivity (∼0.2 mS cm-1) on par with reported performance from other conventional thermo-mechanical routes. These novel solution-phase approaches showcase the diversity and application of wet chemistry in producing selenide-based electrolytes for all-solid-state sodium batteries.

Improving the Initial Coulombic Efficiency of Sodium-Storage Antimony Anodes via Electrochemically Alloying Bismuth

Improving cycling stability while maintaining a high initial Coulombic efficiency (ICE) of the antimony (Sb) anode is always a trade-off for the design of electrodes of sodium-ion batteries (SIBs). Herein, we prepare a carbon-free Sb8Bi1 anode with an ICE of 87.1% at 0.1 A g-1 by a one-step electrochemical reduction of Sb2O3 and Bi2O3 in alkaline solutions. The improved ICE of the Sb8Bi1 anode is due to the alloying of bismuth (Bi) that prevents irreversible interfacial reactions during the sodiation process. Unlike carbon buffers, the use of Bi will reduce the number of side reactions between the carbon buffer and sodium. Moreover, Bi2O3 can promote the reduction of Sb2O3 and reduce the particle size of Sb from ∼20 μm to below 300 nm. The electrolytic products can be modulated by controlling the cell voltages and electrolysis time. The electrolytic Sb8Bi1 anode delivered a capacity of 625 mAh g-1 after 200 cycles with an ICE of 87.1% at 0.1 A g-1 and even 625 mAh g-1 at 1 A g-1 over 100 cycles. Hence, alloying Bi into Sb is an effective way to make a long-lasting Sb anode while maintaining a high Coulombic efficiency.

Synergistically boosting reaction kinetics and suppressing polyselenide shuttle effect by Ti3C2Tx/Sb2Se3 film anode in high-performance sodium-ion batteries

Antimony selenide (Sb₂Se₃), with rich resources and high electrochemical activity, including in conversion and alloying reactions, has been regarded as an ideal candidate anode material for sodium-ion batteries. However, the severe volume expansion, sluggish kinetics, and polyselenide shuttle of the Sb₂Se₃-based anode lead to serious pulverization at high current density, restricting its industrialization. Herein, a unique structure of Sb₂Se₃ nanowires uniformly anchored between Ti₃C₂T_x (MXene) nanosheets was prepared by the electrostatic self-assembly method. The MXene can impede the volume expansion of Sb₂Se₃ nanowires in the sodiation process. Moreover, the Sb₂Se₃ nanowires can reduce the restacking of Ti₃C₂T_x nanosheets and enhance electrolyte accessibility. Furthermore, density functional theory calculations confirm the increased reaction kinetics and better sodium storage capability through the composite of Ti₃C₂T_x with Sb₂Se₃ and the high adsorption capability of Ti₃C₂T_x to polyselenides. Therefore, the resultant Sb₂Se₃/Ti₃C₂T_x anodes show high rate capability (369.4 mAh/g at 5 A/g) and cycling performance (568.9 and 304.1 mAh/g at 0.1 A/g after 100 cycles and at 1.0 A/g after 500 cycles). More importantly, the full sodium-ion batteries using the Sb₂Se₃/Ti₃C₂T_x anode and Na₃V₂(PO₄)₃/carbon cathode exhibit high energy/power densities and outstanding cycle performance.

Hybrid Nano Flake-like Vanadium Diselenide Combined on Multi-Walled Carbon Nanotube as a Binder-Free Electrode for Sodium-Ion Batteries

As the market for electric vehicles and portable electronic devices continues to grow rapidly, sodium-ion batteries (SIBs) have emerged as energy storage systems to replace lithium-ion batteries (LIBs). However, sodium-ion is heavier and larger than lithium-ion, resulting in volume expansion and slower ion transfer. It is necessary to find suitable anode materials with high capacity and stability. In addition, wearable electronics are starting to be commercialized, requiring a binder-free electrode used in flexible batteries. In this work, we synthesized nano flake-like VSe₂ using organic precursor and combined it with MWCNT as carbonaceous material. VSe₂@MWCNT was mixed homogenously using sonication and fabricated film electrodes without a binder and substrate via vacuum filter. The hybrid electrode exhibited high-rate capability and stable cycling performance with a discharge capacity of 469.1 mAhg^-1 after 200 cycles. Furthermore, VSe₂@MWCNT exhibited coulombic efficiency of ~99.7%, indicating good cycle stability. Additionally, VSe₂@MWCNT showed a predominant 85.5% of capacitive contribution at a scan rate of 1 mVs^-1 in sodiation/desodiation process. These results showed that VSe₂@MWCNT is a suitable anode material for flexible SIBs.

Layer-Structured Anisotropic Metal Chalcogenides: Recent Advances in Synthesis, Modulation, and Applications

The unique electronic and catalytic properties emerging from low symmetry anisotropic (1D and 2D) metal chalcogenides (MCs) have generated tremendous interest for use in next generation electronics, optoelectronics, electrochemical energy storage devices, and chemical sensing devices. Despite many proof-of-concept demonstrations so far, the full potential of anisotropic chalcogenides has yet to be investigated. This article provides a comprehensive overview of the recent progress made in the synthesis, mechanistic understanding, property modulation strategies, and applications of the anisotropic chalcogenides. It begins with an introduction to the basic crystal structures, and then the unique physical and chemical properties of 1D and 2D MCs. Controlled synthetic routes for anisotropic MC crystals are summarized with example advances in the solution-phase synthesis, vapor-phase synthesis, and exfoliation. Several important approaches to modulate dimensions, phases, compositions, defects, and heterostructures of anisotropic MCs are discussed. Recent significant advances in applications are highlighted for electronics, optoelectronic devices, catalysts, batteries, supercapacitors, sensing platforms, and thermoelectric devices. The article ends with prospects for future opportunities and challenges to be addressed in the academic research and practical engineering of anisotropic MCs.

One dimensional MOSFETs for sub-5 nm high-performance applications: a case of Sb2Se3 nanowires

Low-dimensional materials have been proposed as alternatives to silicon-based field-effect transistor (FET) channel materials in order to overcome the scaling limitation. In the present research, gate-all-around (GAA) Sb₂Se₃ nanowire FETs were simulated using the ab initio quantum transport method. The gate-length (L_g, L_g = 5 nm) GAA Sb₂Se₃ FETs with an underlap (UL, UL = 2, 3 nm) could satisfy the on-state current (I_on) and delay time (τ) of the 2028 requirements for high performance (HP) applications of the International Technology Roadmap for Semiconductors (ITRS) 2013. It is interesting that the L_g = 3 nm GAA Sb₂Se₃ FETs with a UL = 3 nm can meet the I_on, power dissipation (PDP), and τ of the 2028 requirements of ITRS 2013 for HP applications. Therefore, GAA Sb₂Se₃ FETs can be a potential candidate scaling Moore's law downward to 3 nm.

Crystal Growth Promotion and Defect Passivation by Hydrothermal and Selenized Deposition for Substrate-Structured Antimony Selenosulfide Solar Cells

Antimony sulfide-selenide (Sb₂(S,Se)₃) is a promising light-harvesting material for stable and high-efficiency thin-film photovoltaics (PV) because of its excellent light-harvesting capability, abundant elemental storage, and excellent stability. This study aimed to expand the application of Sb₂(S,Se)₃ solar cells with a substrate structure as a flexible or tandem device. The use of a hydrothermal method accompanied by a postselenization process for the deposition of Sb₂(S,Se)₃ film based on the solar cell substrate structure was first demonstrated. The mechanism of postselenization treatment on crystal growth promotion of the Sb₂(S,Se)₃ film and the defect passivation of the Sb₂(S,Se)₃ solar cell were revealed through different characterization methods. The crystallinity and the carrier transport property of the Sb₂(S,Se)₃ film improved, and both the interface defect density of the Sb₂(S,Se)₃/CdS interface and the bulk defect density of the Sb₂(S,Se)₃ absorber decreased. Through these above-mentioned processes, the transport and collection of electronics can be improved, and the defect recombination loss can be reduced. By using postselenization treatment to optimize the absorber layer, Sb₂(S,Se)₃ solar cells with the configuration SLG/Mo/Sb₂(S,Se)₃/CdS/ITO/Ag achieved an efficiency of 4.05%. This work can provide valuable information for the further development and improvement of Sb₂(S,Se)₃ solar cells.

Recent Advancements in Chalcogenides for Electrochemical Energy Storage Applications

Energy storage has become increasingly important as a study area in recent decades. A growing number of academics are focusing their attention on developing and researching innovative materials for use in energy storage systems to promote sustainable development goals. This is due to the finite supply of traditional energy sources, such as oil, coal, and natural gas, and escalating regional tensions. Because of these issues, sustainable renewable energy sources have been touted as an alternative to nonrenewable fuels. Deployment of renewable energy sources requires efficient and reliable energy storage devices due to their intermittent nature. High-performance electrochemical energy storage technologies with high power and energy densities are heralded to be the next-generation storage devices. Transition metal chalcogenides (TMCs) have sparked interest among electrode materials because of their intriguing electrochemical properties. Researchers have revealed a variety of modifications to improve their electrochemical performance in energy storage. However, a stronger link between the type of change and the resulting electrochemical performance is still desired. This review examines the synthesis of chalcogenides for electrochemical energy storage devices, their limitations, and the importance of the modification method, followed by a detailed discussion of several modification procedures and how they have helped to improve their electrochemical performance. We also discussed chalcogenides and their composites in batteries and supercapacitors applications. Furthermore, this review discusses the subject’s current challenges as well as potential future opportunities.

Heterojunction-Promoted Sodium Ion Storage of Bimetallic Selenides Encapsulated in a Carbon Sheath with Boosted Ion Diffusion and Stable Structure

Although metallic chalcogenides are deemed as attractive sodium anode materials recently, the electrochemical performance is severely confined by the liability of structural collapse and sluggish ion diffusion kinetics. Herein a composite of carbon-encapsulated bimetallic selenides MoSe₂-Sb₂Se₃ was prepared by a hydrothermal method on the basis of abundant reaction sites, high activity, an extra built-in electric field generated from heterointerfaces, and synergistic effects between the different components. Equally important, the carbon coating is effective to support the structural stability by restraining the vast volumetric variation to achieve the purpose of improving the cycling performance. The density functional theory calculation results indicate that the band gap is narrowed and that the work function is decreased on the interface of the MoSe₂-Sb₂Se₃ heterojunction, leading to an additional driving force stemming from the introduction of the built-in electric field and the formation of the Sb-Se (Se from MoSe₂) bond. Therefore, the resultant composite presents increased reaction kinetics and good electrochemical properties by acquiring a capacity of 376.0 mA h g^-1 over 580 cycles at 2.0 A g^-1 for the half-cell and 276 mA h g^-1 over 750 cycles at 2 A g^-1 for the full-cell. This work highlights bimetallic selenides with facilitated ion transferability with high performance.

Engineering Nanostructured Antimony-Based Anode Materials for Sodium Ion Batteries

Sodium-ion batteries (SIBs) are considered a potential alternative to lithium-ion batteries (LIBs) for energy storage due to their low cost and the large abundance of sodium resources. The search for new anode materials for SIBs has become a vital approach to satisfying the ever-growing demands for better performance with higher energy/power densities, improved safety and a longer cycle life. Recently, antimony (Sb) has been extensively researched as a promising candidate due to its high specific capacity through an alloying/dealloying process. In this review article, we will focus on different categories of the emerging Sb based anode materials with distinct sodium storage mechanisms including Sb, two-dimensional antimonene and antimony chalcogenide (Sb2S3 and Sb2Se3). For each part, we emphasize that the novel construction of an advanced nanostructured anode with unique structures could effectively improve sodium storage properties. We also highlight that sodium storage capability can be enhanced through designing advanced nanocomposite materials containing Sb based materials and other carbonaceous modification or metal supports. Moreover, the recent advances in operando/in-situ investigation of its sodium storage mechanism are also summarized. By providing such a systematic probe, we aim to stress the significance of novel nanostructures and advanced compositing that would contribute to enhanced sodium storage performance, thus making Sb based materials as promising anodes for next-generation high-performance SIBs.

Close-spaced thermally evaporated 3D Sb2Se3 film for high-rate and high-capacity lithium-ion storage

As a key factor for fast-charging lithium-ion batteries (LIBs), high-rate anode materials that can recharge in a few minutes have aroused increasing attention. However, high-rate performance is always accompanied by low theoretical capacities, such as the widely known high-rate electrode of Li4Ti5O12 (175 mA h g-1), which severely limits its large-scale implementation in the development of high power density LIBs. Here, we report a modified close-spaced thermal evaporation process to deposit 3D-structured Sb2Se3 films (3D-SSF) with tunable morphology as an additive-free anode for LIBs. After a high-rate activation process, 3D-SSF exhibits a flatter discharge plateau than the reported results and could deliver a high capacity of 471 mA h g-1 at an ultrahigh current density of 21 440 mA g-1, which is superior to the widely known high-rate Li4Ti5O12 anode (over 150 mA h g-1 at 8750 mA g-1). Moreover, we reveal a current-regulated Li-ion storage mechanism where 3D-SFF undergoes a synergistic conversion and alloying reaction at low current densities, while an alloying reaction-dominated process at high rates. Beyond that, full batteries with excellent rate performance were successfully assembled by pairing with homemade LiFePO4 (LFP) as the cathode.

Dual carbon-confined Sb2Se3 nanoparticles with pseudocapacitive properties for high-performance lithium-ion half/full batteries

Transition metal selenides have attracted enormous research attention as anodes for lithium-ion batteries (LIBs) due to their high theoretical specific capacities. Nevertheless, the low electronic conductivity and dramatic volume variation in electrochemical reaction processes result in rapid capacity fading and poor rate capability. Herein, a metal-organic framework is used as a template to in situ synthesize Sb₂Se₃ nanoparticles encapsulated in N-doped carbon nanotubes (N-CNTs) grafted on reduced graphene oxide (rGO) nanosheets. The synergistic effects of N-doped carbon nanotubes and reduced graphene oxide nanosheets are beneficial for providing good electrical conductivity and maintaining the structural stability of electrode materials, leading to stable cycling performance and superior rate performance. Kinetic analysis suggests that the electrochemical reaction kinetics is dominated by pseudocapacitive contribution. Notably, a high discharge capacity of 451.1 mA h g^-1 at a current density of 2.0 A g^-1 is delivered after 450 cycles. Even at a high current density of 10.0 A g^-1, a discharge capacity of 192.6 mA h g^-1 is maintained after 10 000 cycles. When coupled with a commercial LiFePO₄ cathode, the full batteries show an excellent discharge specific capacity of 534.5 mA h g^-1 at 0.2 A g^-1. This work provides an effective strategy for constructing high-performance anodes for Li⁺ storage.

Thermoelectric properties of antimony selenide hexagonal nanotubes

Antimony selenide (Sb₂Se₃) is a material widely used in photodetectors and relatively new as a possible material for thermoelectric applications. Taking advantage of the new properties after nanoscale fabrication, this material shows great potential for the development of efficient low temperature thermoelectric devices. Here we study the synthesis, the crystal properties and the thermal and thermoelectric transport response of Sb₂Se₃ hexagonal nanotubes (HNT) in the temperature range between 120 and 370 K. HNT have a moderate electrical conductivity ∼10² S m^-1 while maintaining a reasonable Seebeck coefficient ∼430 μV K^-1 at 370 K. The electrical conductivity in Sb₂Se₃ HNT is about 5 orders of magnitude larger and its thermal conductivity one half of what is found in bulk. Moreover, the calculated figure of merit (ZT) at room temperature is the largest value reported in antimony selenide 1D structures.

Ultra-stable Sb confined into N-doped carbon fibers anodes for high-performance potassium-ion batteries

Antimony-based materials with high theoretical capacity are known as promising anodes for potassium-ion batteries (PIBs). However, they still face challenges from the large ionic radius of the K ion, which has sluggish kinetics. Much effort is needed to exploit high-performance electrode materials to satisfy the reversible capacity of PIBs. In this paper, nano Sb confined in N-doped carbon fibers (Sb@CN nanofibers) were successfully prepared through an electrospinning method, which was designed to improve potassium storage performances. Sb@CN nanofibers benefit from the fact that the synergy between the porous nanofiber frame structure and the uniformly distributed Sb nano-components in the carbon matrix can effectively accelerate the ion migration rate and reduce the mechanical stress caused by K⁺ insertion/extraction, Sb@CN nanofiber electrodes thus exhibited excellent potassium storage performance, especially long cycle stability, as expected. When utilized as a PIB anode, they delivered high reversible capacity of 360.2 mAh g^-1 after 200 cycles at 50 mA g^-1, and a particularly stable capacity of 212.7 mAh g^-1 was also obtained after 1000 cycles even at 5000 mA g^-1. Given such outstanding electrochemical performances, this work is expected to provide insight into the development and exploration of advanced alloy-type electrodes for PIBs.

High Na+ Mobility in rGO Wrapped High Aspect Ratio 1D SbSe Nano Structure Renders Better Electrochemical Na+ Battery Performance

We chose to understand the cyclic instability and rate instability issues in the promising class of Na⁺ conversion and alloying anodes with Sb₂ Se₃ as a typical example. We employ a synthetic strategy that ensures efficient rGO (reduced graphene oxide) wrapping over Sb₂ Se₃ material. By utilization of the minimum weight of additive (5 wt.% of rGO), we achieved a commendable performance with a reversible capacity of 550 mAh g^-1 at a specific current of 100 mA g^-1 and an impressive rate performance with 100 % capacity retention after high current cycling involving a 2 Ag^-1 intermediate current step. The electrochemical galvanostatic intermittent titration technique (GITT) has been employed for the first time to draw a rationale between the enhanced performance and the increased mobility in the rGO wrapped composite (Sb₂ Se₃ -rGO) compared to bare Sb₂ Se₃ . GITT analysis reveals higher Na⁺ diffusion coefficients (approx. 30 fold higher) in the case of Sb₂ Se₃ -rGO as compared to bare Sb₂ Se₃ throughout the operating voltage window. For Sb₂ Se₃ -rGO the diffusion coefficients in the range of 8.0×10^-15  cm²  s^-1 to 2.2×10^-12  cm²  s^-1 were observed, while in case of bare Sb₂ Se₃ the diffusion coefficients in the range of 1.6×10^-15  cm²  s^-1 to 9.4×10^-15  cm²  s^-1 were observed.

Structural Reorganization-Based Nanomaterials as Anodes for Lithium-Ion Batteries: Design, Preparation, and Performance

In recent years, with the growing demand for higher capacity, longer cycling life, and higher power and energy density of lithium ion batteries (LIBs), the traditional insertion-based anodes are increasingly considered out of their depth. Herein, attention is paid to the structural reorganization electrode, which is the general term for conversion-based and alloying-based materials according to their common characteristics during the lithiation/delithiation process. This Review summarizes the recent achievements in improving and understanding the lithium storage performance of conversion-based anodes (especially the most widely studied transition metal oxides like Mn-, Fe-, Co-, Ni-, and Cu-based oxides) and alloying-based anodes (mainly including Si-, Sn-, Ge-, and Sb-based materials). The synthesis schemes, morphological control and reaction mechanism of these materials are also included. Finally, viewpoints about the challenges and feasible improvement measures for future development in this direction are given. The aim of this Review is to shed some light on future electrode design trends of structural reorganization anode materials for LIBs.

A fluorinated alloy-type interfacial layer enabled by metal fluoride nanoparticle modification for stabilizing Li metal anodes

Using highly dispersed metal fluoride nanoparticles to construct a uniform fluorinated alloy type interfacial layer on the surface of Li metal anodes is realized by an ex situ solution chemical modification method. The fluorinated alloy-type interfacial layer can effectively inhibit the growth of undesirable Li dendrites while enhancing the performance of Li metal anodes.

Vanadium-based nanowires for sodium-ion batteries

Sodium-ion batteries (SIBs) have received great attention because of the abundance source and low cost. To date, some Na⁺ storage materials have achieved great performance, but the larger Na⁺ radius and more complex Na⁺ storage mechanism compared with Li⁺ still limit the energy density and power density. This review systematically summarizes emerging synthetic technologies of vanadium-based materials from simple nanowires to complicated modified/optimized structures. In addition, vanadium-based nanowire materials are reviewed at both the cathode and anode side, and advantages and drawbacks are proposed to explain the challenges facing application of novel materials. Furthermore, a vanadium-based single-nanowire device is reported to reveal the Na⁺ storage mechanism, which contributes to the understanding of the reaction in SIBs. Finally, this review summarizes the current development challenges of SIBs and looks forward to the future development prospects of vanadium-based nanowires, providing a new direction for further applications of SIBs.

Carbon-Based Alloy-Type Composite Anode Materials toward Sodium-Ion Batteries

In the scenario of renewable clean energy gradually replacing fossil energy, grid-scale energy storage systems are urgently necessary, where Na-ion batteries (SIBs) could supply crucial support, due to abundant Na raw materials and a similar electrochemical mechanism to Li-ion batteries. The limited energy density is one of the major challenges hindering the commercialization of SIBs. Alloy-type anodes with high theoretical capacities provide good opportunities to address this issue. However, these anodes suffer from the large volume expansion and inferior conductivity, which induce rapid capacity fading, poor rate properties, and safety issues. Carbon-based alloy-type composites (CAC) have been extensively applied in the effective construction of anodes that improved electrochemical performance, as the carbon component could alleviate the volume change and increase the conductivity. Here, state-of-the-art CAC anode materials applied in SIBs are summarized, including their design principle, characterization, and electrochemical performance. The corresponding alloying mechanism along with its advantages and disadvantages is briefly presented. The crucial roles and working mechanism of the carbon matrix in CAC anodes are discussed in depth. Lastly, the existing challenges and the perspectives are proposed. Such an understanding critically paves the way for tailoring and designing suitable alloy-type anodes toward practical applications.

Construction of Sb2Se3 nanocrystals on Cu2−xSe@C nanosheets for high performance lithium storage

Cu_2−xSe@C@Sb₂Se₃ with enhanced electrochemical performance was designed and fabricated, where Sb₂Se₃ nanoparticles were anchored on Cu_2−xSe@C nanosheets.

Recent Advances in Nanowire-Based, Flexible, Freestanding Electrodes for Energy Storage

The rational design of flexible electrodes is essential for achieving high performance in flexible and wearable energy-storage devices, which are highly desired with fast-growing demands for flexible electronics. Owing to the one-dimensional structure, nanowires with continuous electron conduction, ion diffusion channels, and good mechanical properties are particularly favorable for obtaining flexible freestanding electrodes that can realize high energy/power density, while retaining long-term cycling stability under various mechanical deformations. This Minireview focuses on recent advances in the design, fabrication, and application of nanowire-based flexible freestanding electrodes with diverse compositions, while highlighting the rational design of nanowire-based materials for high-performance flexible electrodes. Existing challenges and future opportunities towards a deeper fundamental understanding and practical applications are also presented.

Hierarchically Porous Fe2 CoSe4 Binary-Metal Selenide for Extraordinary Rate Performance and Durable Anode of Sodium-Ion Batteries

Owing to high energy capacities, transition metal chalcogenides have drawn significant research attention as the promising electrode materials for sodium-ion batteries (SIBs). However, limited cycle life and inferior rate capabilities still hinder their practical application. Improvement of the intrinsic conductivity by smart choice of elemental combination along with carbon coupling of the nanostructures may result in excellence of rate capability and prolonged cycling stability. Herein, a hierarchically porous binary transition metal selenide (Fe2 CoSe4 , termed as FCSe) nanomaterial with improved intrinsic conductivity was prepared through an exclusive methodology. The hierarchically porous structure, intimate nanoparticle-carbon matrix contact, and better intrinsic conductivity result in extraordinary electrochemical performance through their synergistic effect. The synthesized FCSe exhibits excellent rate capability (816.3 mA h g-1 at 0.5 A g-1 and 400.2 mA h g-1 at 32 A g-1 ), extended cycle life (350 mA h g-1 even after 5000 cycles at 4 A g-1 ), and adequately high energy capacity (614.5 mA h g-1 at 1 A g-1 after 100 cycles) as anode material for SIBs. When further combined with lab-made Na3 V2 (PO4 )3 /C cathode in Na-ion full cells, FCSe presents reasonably high and stable specific capacity.

The State and Challenges of Anode Materials Based on Conversion Reactions for Sodium Storage

Sodium-ion batteries (SIBs) have huge potential for applications in large-scale energy storage systems due to their low cost and abundant sources. It is essential to develop new electrode materials for SIBs with high performance in terms of energy density, cycle life, and cost. Metal binary compounds that operate through conversion reactions hold promise as advanced anode materials for sodium storage. This Review highlights the storage mechanisms and advantages of conversion-type anode materials and summarizes their recent development. Although conversion-type anode materials have high theoretical capacities and abundant varieties, they suffer from multiple challenging obstacles to realize commercial applications, such as low reversible capacity, large voltage hysteresis, low initial coulombic efficiency, large volume changes, and low cycling stability. These key challenges are analyzed in this Review, together with emerging strategies to overcome them, including nanostructure and surface engineering, electrolyte optimization, and battery configuration designs. This Review provides pertinent insights into the prospects and challenges for conversion-type anode materials, and will inspire their further study.

A Dealloying Synthetic Strategy for Nanoporous Bismuth-Antimony Anodes for Sodium Ion Batteries

Metal-based anodes have recently aroused much attention in sodium ion batteries (SIBs) owing to their high theoretical capacities and low sodiation potentials. However, their progresses are prevented by the inferior cycling performance caused by severe volumetric change and pulverization during the (de)sodiation process. To address this issue, herein an alloying strategy was proposed and nanoporous bismuth (Bi)-antimony (Sb) alloys were fabricated by dealloying of ternary Mg-based precursors. As an anode for SIBs, the nanoporous Bi₂Sb₆ alloy exhibits an ultralong cycling performance (10 000 cycles) at 1 A/g corresponding to a capacity decay of merely 0.0072% per cycle, due to the porous structure, alloying effect and proper Bi/Sb atomic ratio. More importantly, a (de)sodiation mechanism ((Bi,Sb) ↔ Na(Bi,Sb) ↔ Na₃(Bi,Sb)) is identified for the discharge/charge processes of Bi-Sb alloys by using operando X-ray diffraction and density functional theory calculations.

Heterostructured Bi2S3-Bi2O3 Nanosheets with a Built-In Electric Field for Improved Sodium Storage

Constructing novel heterostructures has great potential in tuning the physical/chemical properties of functional materials for electronics, catalysis, as well as energy conversion and storage. In this work, heterostructured Bi₂S₃-Bi₂O₃ nanosheets (BS-BO) have been prepared through an easy water-bath approach. The formation of such unique BS-BO heterostructures was achieved through a controllable thioacetamide-directed surfactant-assisted reaction process. Bi₂O₃ sheets and Bi₂S₃ sheets can be also prepared through simply modifying the synthetic recipe. When employed as the sodium-ion battery anode material, the resultant BS-BO displays a reversible capacity of ∼630 mA h g^-1 at 100 mA g^-1. In addition, the BS-BO demonstrates improved rate capability and enhanced cycle stability compared to its Bi₂O₃ sheets and Bi₂S₃ sheets counterparts. The improved electrochemical performance can be ascribed to the built-in electric field in the BS-BO heterostructure, which effectively facilitates the charge transport. This work would shed light on the construction of novel heterostructures for high-performance sodium-ion batteries and other energy-related devices.

Composition-Dependent Aspect Ratio and Photoconductivity of Ternary (BixSb1-x)2S3 Nanorods

The chemical composition, size and shape, and surface engineering play key roles in the performance of electronic, optoelectronic, and energy devices. V₂VI₃ (V = Sb, Bi; VI = S, Se) group materials are actively studied in these fields. In this paper, we introduce a colloidal method to synthesize uniform ternary (Bi_xSb_1-x)₂S₃ (0 < x < 1) nanorods. These nanorods show composition-dependent aspect ratios, enabling their composition, size, and shape control by varying Bi/Sb precursor ratios. It is found that the surface passivation by various thiols (L-SH) efficiently enhances the photoconductivity and optical responsive capability of (Bi_xSb_1-x)₂S₃ nanorods when used as active materials in indium tin oxide (ITO)/(Bi_xSb_1-x)₂S₃/ITO optoelectronic devices. Meanwhile, the increase of Sb content causes a gradual deterioration of photoconductivity of thiol-passivated nanorods. We propose that the thiol passivation is able to reduce the number of S vacancies, which act as the recombination centers (trapped states) for photogenerated electrons and holes, and thus boosts the carrier transport in (Bi_xSb_1-x)₂S₃ nanorods, and in particular that the composition-related conductivity deterioration is attributed to the increase of unpassivated S vacancies and surface oxidation due to the rise of Sb content.

1D Nanomaterials: Design, Synthesis, and Applications in Sodium-Ion Batteries

Sodium-ion batteries (SIBs) have received extensive attention as ideal candidates for large-scale energy storage systems (ESSs) owing to the rich resources and low cost of sodium (Na). However, the larger size of Na⁺ and the less negative redox potential of Na⁺ /Na result in low energy densities, short cycling life, and the sluggish kinetics of SIBs. Therefore, it is necessary to develop appropriate Na storage electrode materials with the capability to host larger Na⁺ and fast ion diffusion kinetics. 1D materials such as nanofibers, nanotubes, nanorods, and nanowires, are generally considered to be high-capacity and stable electrode materials, due to their uniform structure, orientated electronic and ionic transport, and strong tolerance to stress change. Here, the synthesis of 1D nanomaterials and their applications in SIBs are reviewed. In addition, the prospects of 1D nanomaterials on energy conversion and storage as well as the development and application orientation of SIBs are presented.

Scalable Low-Band-Gap Sb2Se3 Thin-Film Photocathodes for Efficient Visible-Near-Infrared Solar Hydrogen Evolution

A highly efficient low-band-gap (1.2-0.8 eV) photoelectrode is critical for accomplishing efficient conversion of visible-near-infrared sunlight into storable hydrogen. Herein, we report an Sb₂Se₃ polycrystalline thin-film photocathode having a low band gap (1.2-1.1 eV) for efficient hydrogen evolution for wide solar-spectrum utilization. The photocathode was fabricated by a facile thermal evaporation of a single Sb₂Se₃ powder source onto the Mo-coated soda-lime glass substrate, followed by annealing under Se vapor and surface modification with an antiphotocorrosive CdS/TiO₂ bilayer and Pt catalyst. The fabricated Sb₂Se₃(Se-annealed)/CdS/TiO₂/Pt photocathode achieves a photocurrent density of ca. -8.6 mA cm^-2 at 0 V_RHE, an onset potential of ca. 0.43 V_RHE, a stable photocurrent for over 10 h, and a significant photoresponse up to the near-infrared region (ca. 1040 nm) in near-neutral pH buffered solution (pH 6.5) under AM 1.5G simulated sunlight. The obtained photoelectrochemical performance is attributed to the reliable synthesis of a micrometer-sized Sb₂Se₃ (Se-annealed) thin film as photoabsorber and the successful construction of an appropriate p-n heterojunction at the electrode-liquid interface for effective charge separation. The demonstration of a low-band-gap and high-performance Sb₂Se₃ photocathode with facile fabrication might facilitate the development of cost-effective PEC devices for wide solar-spectrum utilization.

Alloy-Based Anode Materials toward Advanced Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are considered as promising alternatives to lithium-ion batteries owing to the abundant sodium resources. However, the limited energy density, moderate cycling life, and immature manufacture technology of SIBs are the major challenges hindering their practical application. Recently, numerous efforts are devoted to developing novel electrode materials with high specific capacities and long durability. In comparison with carbonaceous materials (e.g., hard carbon), partial Group IVA and VA elements, such as Sn, Sb, and P, possess high theoretical specific capacities for sodium storage based on the alloying reaction mechanism, demonstrating great potential for high-energy SIBs. In this review, the recent research progress of alloy-type anodes and their compounds for sodium storage is summarized. Specific efforts to enhance the electrochemical performance of the alloy-based anode materials are discussed, and the challenges and perspectives regarding these anode materials are proposed.

Synthesis of long hierarchical MoS2 nanofibers assembled from nanosheets with an expanded interlayer distance for achieving superb Na-ion storage performance

MoS₂ material is considered as a promising anode material candidate in Na-ion batteries (NIBs) due to its high theoretical capacity and layered structure. However, MoS₂ nanosheets usually tend to restack or aggregate during the synthesis and cycling process, which makes the advantages of the separated nanosheets disappear. Here, we present a PVP-assisted synthesis for growing long hierarchical MoS₂ nanofibers with a length up to 74.5 μm, which were further assembled from intercrossed curly nanosheets with expanded (002) interlayer spacings in the range of 0.62 nm to 1.14 nm. Such architectural design simultaneously combines multiple-scale structural features that are desired for Na-ion storage. On the one hand, the nanosheets can provide a large surface area which is in contact with the electrolyte, a short Na-ion diffusion pathway from the lateral side and facile Na-ion insertion and extraction through the expanded (002) interlayer; on the other hand, the hierarchical MoS₂ nanofibers possess a one dimensional structure and a suitable amount of carbon, which can both serve as an electrical highway and prevent them from restacking, resulting in an enhanced electrochemical performance. When used as an anode in NIBs, they demonstrated excellent cycling performance (537 mA h g^-1 at 0.1 A g^-1 after 200 cycles, and 370 mA h g^-1 at 2 A g^-1 over 200 cycles) and outstanding rate capability (329 mA h g^-1 at 10 A g^-1).

Rodlike Sb2Se3 Wrapped with Carbon: The Exploring of Electrochemical Properties in Sodium-Ion Batteries

One-dimensional Sb₂Se₃/C rods are prepared through self-assembly by inducing anisotropy, and their corresponding sodium storage behaviors are evaluated, presenting excellent electrochemical performances with superior cycling stability and rate capability. Sb₂Se₃ delivers a high initial charge capacity of 657.6 mA h g^-1 at a current density of 0.2 A g^-1 between 2.5 and 0.01 V. After 100 cycles, the reversible capacity of Sb₂Se₃/C is still retained at 485.2 mA h g^-1. Even at a high rate current density of 2.0 A g^-1, the charge capacity is still retained at 311.5 mA h g^-1. Through the analysis of cyclic voltammetry and in situ electrochemical impedance spectroscopy, the in-depth understanding of high rate performances is explored effectively. Briefly, the sodium storage performance of Sb₂Se₃/C is observably enhanced, benefiting from the 1D structure and the introduction of a carbon layer with robust structure stability and conductivity.

H2V3O8 Nanowires as High-Capacity Cathode Materials for Magnesium-Based Battery

Magnesium-based batteries have received much attention as promising candidates to next-generation batteries because of high volumetric capacity, low price, and dendrite-free property of Mg metal. Herein, we reported H₂V₃O₈ nanowire cathode with excellent electrochemical property in magnesium-based batteries. First, it shows a satisfactory magnesium storage ability with 304.2 mA h g^-1 capacity at 50 mA g^-1. Second, it possesses a high-voltage platform of ∼2.0 V vs Mg/Mg²⁺. Furthermore, when evaluated as a cathode material for magnesium-based hybrid Mg²⁺/Li⁺ battery, it exhibits a high specific capacity of 305.4 mA h g^-1 at 25 mA g^-1 and can be performed in a wide working temperature range (-20 to 55 °C). Notably, the insertion-type ion storage mechanism of H₂V₃O₈ nanowires in hybrid Mg²⁺/Li⁺ batteries are investigated by ex situ X-ray diffraction and Fourier transform infrared. This research demonstrates that the H₂V₃O₈ nanowire cathode is a potential candidate for high-performance magnesium-based batteries.

Hollow-sphere ZnSe wrapped around carbon particles as a cycle-stable and high-rate anode material for reversible Li-ion batteries

Hollow-sphere ZnSe is successfully obtained through Ostwald ripening. Carbon nanoparticles are designed and utilized to form a wrapped carbon network as a conductive buffering matrix by subsequent annealing.