Advances and Challenges in Metal Sulfides/Selenides for Next-Generation Rechargeable Sodium-Ion Batteries

Colloidal Synthesis and Analysis of CNT-Cu2S for Stability and Capacity Increase Alleviation in Sodium-Ion Storage

With the growing interest in energy storage, significant research has focused on finding suitable anode materials for sodium-ion batteries (SIBs). While developing high-capacity nanosized metal sulfides, issues like low stability and rapid initial capacity decline are common. Instead of maintaining steady capacity, they also tend to exhibit an increase in discharge capacity as cycling continues. We introduce CNT-Cu2S, featuring Cu2S nanoplates integrated onto the surface of MWCNTs, and assess its electrochemical properties for SIBs. Cu2S initially exhibited a rapid decrease in capacity and then showed increased capacity. In contrast, CNT-Cu2S demonstrated a stable capacity of 344.8 mAh g-1 at 2.0 A g-1 over 800 cycles, close to the theoretical capacity with capacitive behavior. This paper carried out analysis using data from in situ EIS and overpotential data from GITT to explain the different outcomes between the Cu2S and CNT-Cu2S experiments. These results show that CNT-Cu2S is a suitable anode material for SIBs.

Pre-Intercalation of TMA Cations in MoS2 Interlayers for Fast and Stable Zinc Ion Storage

Applications of aqueous zinc ion batteries (ZIBs) for grid-scale energy storage are hindered by the lacking of stable cathodes with large capacity and fast redox kinetics. Herein, the intercalation of tetramethylammonium (TMA+) cations is reported into MoS2 interlayers to expand its spacing from 0.63 to 1.06 nm. The pre-intercalation of TMA+ induces phase transition of MoS2 from 2H to 1T phase, contributing to an enhanced conductivity and better wettability. Besides, The calculation from density functional theory indicates that those TMA+ can effectively shield the interactions between Zn2+ and MoS2 layers. Consequently, two orders magnitude high Zn2+ ions diffusion coefficient and 11 times enhancement in specific capacity (212.4 vs 18.9 mAh g‒1 at 0.1 A g‒1) are achieved. The electrochemical investigations reveal both Zn2+ and H+ can be reversibly co-inserted into the MoS2-TMA electrode. Moreover, the steady habitat of TMA+ between MoS2 interlayers affords the MoS2-TMA with remarkable cycling stability (90.1% capacity retention after 2000 cycles at 5.0 A g‒1). These performances are superior to most of the recent zinc ion batteries assembled with MoS2 or VS2-based cathodes. This work offers a new avenue to tuning the structure of MoS2 for aqueous ZIBs.

CoS2/carbon network flexible film with Co-N bond/π-π interaction enables superior mechanical properties and high-rate sodium ion storage

Flexible electrodes based on conversion-type materials have potential applications in low-cost and high-performance flexible sodium-ion batteries (FSIBs), owing to their high theoretical capacity and appropriate sodiation potential. However, they suffer from flexible electrodes with poor mechanical properties and sluggish reaction kinetics. In this study, freestanding CoS2 nanoparticles coupled with graphene oxides and carbon nanotubes (CoS2/GO/CNTs) flexible films with robust and interconnected architectures were successfully synthesized. CoS2/GO/CNTs flexible film displays high electronic conductivity and superior mechanical properties (average tensile strength of 21.27 MPa and average toughness of 393.18 KJ m-3) owing to the defect bridge for electron transfer and the formation of the π-π interactions between CNTs and GO. In addition, the close contact between the CoS2 nanoparticles and carbon networks enabled by the Co-N chemical bond prevents the self-aggregation of the CoS2 nanoparticles. As a result, the CoS2/GO/CNTs flexible film delivered superior rate capability (213.5 mAh g-1 at 6 A g-1, better than most reported flexible anode) and long-term cycling stability. Moreover, the conversion reaction that occurred in the CoS2/GO/CNTs flexible film exhibited pseudocapacitive behavior. This study provides meaningful insights into the development of flexible electrodes with superior mechanical properties and electrochemical performance for energy storage.

Integrating anti-aggregation Ta-Se motifs into copper selenide for fast and robust sodium-ion storage

We report a novel bimetallic selenide Cu3TaSe4 anode for sodium-ion batteries synthesized via a one-step solid-state method. The integration of Ta-Se motifs into copper selenide forms a cubic grid structure that prevents copper atom aggregation and mitigates electrode failure. Cu3TaSe4 exhibits a high specific capacity of 305 mAh g-1 at 1 C, excellent rate performance of 286 mAh g-1 at 50 C, and superior cycling stability with 272 mAh g-1 after 3500 cycles at 20 C. This work demonstrates the potential of bimetallic selenides in enhancing sodium-ion battery performance.

Interlayer Space Engineering-Induced Pseudocapacitive Zinc-Ion Storage in Holey Graphene Oxide-Bearing Vertically Oriented MoS2 Nano-Wall Array Cathode for Aqueous Rechargeable Zn Metal Batteries

Transition metal dichalcogenides, particularly MoS2, are acknowledged as a promising cathode material for aqueous rechargeable zinc metal batteries (ARZMBs). Nevertheless, its lack of hydrophilicity, poor electrical conductivity, significant restacking, and restricted interlayer spacing translate into inadequate capacity and rate performance. Herein, the unique porous structure and additional functional groups present in holey graphene oxide (hGO) are taken advantage of to dictate the vertical growth pattern of oxygen-doped MoS2 nanowalls (O-MoS2/NW) over the hGO surface. Compared to conventional graphene oxide (GO), the presence of nano-pores in hGO facilitates the homogeneous dispersion of Mo precursors and provides stronger interaction sites, promoting the uniform vertical alignment of O-MoS2/NW. The synergistic interaction between O-MoS2-NW and hGO translates to enhanced electron conductivity, efficient electrolyte penetration, enhanced interlayer spacing, reduced restacking, and enhanced surface area. As a consequence of precise control of various factors that decide the overall battery performance, a high discharge capacity (227 mAh g-1 at 100 mA g-1) cathode material with significantly lower charge transfer resistance (66 Ω) compared to pristine O-MoS2 (153 Ω) is developed. These findings underscore the potential of hGO as a multifunctional platform for nanoengineering high-performance cathode materials for the next generation of efficient and durable ARZMBs.

Synthesis, Modulation, and Application of Two-Dimensional TMD Heterostructures

Two-dimensional (2D) transition metal dichalcogenide (TMD) heterostructures have attracted a lot of attention due to their rich material diversity and stack geometry, precise controllability of structure and properties, and potential practical applications. These heterostructures not only overcome the inherent limitations of individual materials but also enable the realization of new properties through appropriate combinations, establishing a platform to explore new physical and chemical properties at micro-nano-pico scales. In this review, we systematically summarize the latest research progress in the synthesis, modulation, and application of 2D TMD heterostructures. We first introduce the latest techniques for fabricating 2D TMD heterostructures, examining the rationale, mechanisms, advantages, and disadvantages of each strategy. Furthermore, we emphasize the importance of characteristic modulation in 2D TMD heterostructures and discuss some approaches to achieve novel functionalities. Then, we summarize the representative applications of 2D TMD heterostructures. Finally, we highlight the challenges and future perspectives in the synthesis and device fabrication of 2D TMD heterostructures and provide some feasible solutions.

An Engineering Porous Spherical Carbon Cathode for High-Energy Sodium-Ion Capacitor

Sodium-ion hybrid capacitors (SICs) are emerging as promising devices that can balance energy and power output. However, the lack of a high-capacity cathode that can match the anode has limited its further application. In this work, we develop an efficient method to prepare spherical porous carbons (SPCs) with great specific surface area and narrow pore size distribution from coal-based humic acid via spray drying and a subsequent chemical activation process. Thanks to this unique porous structure, the SPC cathode has a superb capacity of 223 F g-1 at 0.05 A g-1, as well as splendid rate performance and cycling stability. SICs constructed by an SPC cathode and hard carbon anode can exhibit a high energy density of 179.8 Wh kg-1 at 155 W kg-1 and achieved 89.4% capacity retention after 10 000 cycles at 0.5 A g-1. This outcome presents a viable approach to attaining high-capacity cathodes for constructing outstanding performance hybrid capacitors.

3D MoS2/graphene oxide integrated composite as anode for high-performance sodium-ion batteries

Sodium-ion batteries (SIBs) are emerging as a promising alternative to conventional lithium-ion technology, due to the abundance of sodium resources. The major drawbacks for the commercial application of SIBs lie in the slow kinetic processes and poor energy density of the devices. Molybdenum sulfide (MoS2), a graphene-like material, is becoming a promising anode material for SIBs, because of its high theoretical capacity (670 mAh g-1) and layered structure that suitable for Na+ intercalation/extraction. However, the intrinsic properties of MoS2, such as low conductivity, slow Na+ diffusion kinetics and large volume change during charging/discharging, restrict its rate capability and cycle stability. Here, molybdenum disulfide and graphene oxide (3D MoS2/GO) with excellent conductivity were fabricated through layer-by-layer method using amino-functionalized SiO2 nanospheres as templates. The 3D MoS2/GO composite demonstrates excellent cycling stability and capacity of 525 mA h g-1 at 500 mA g-1 after 100 cycles, which mainly due to the integrated MoS2/GO components and unique 3D macroporous structure, facilitating the material conductivity and Na+ diffusion rate, while tolerating the volume expansion of MoS2 during the charge/discharge processes.

High-Performance Sodium-Ion Batteries with Graphene: An Overview of Recent Developments and Design

Due to their low production cost, sodium-ion batteries (SIBs) are considered attractive alternatives to lithium-ion batteries (LIBs) for next generation sustainable and large-scale energy storage systems. However, during the charge/discharge cycle, a large volume strain is resulted due to the presence of a large radius of sodium ions and high molar compared to lithium ions, which further leads to poor cyclic stability and lower reversible capacity. In the past, researchers have devoted significant efforts to explore various anode materials to achieve SIBs with high energy density. Hence, as a promising anode material for SIBs, the two-dimensional (2D) materials including graphene and its derivatives and metal oxides have attracted remarkable attention due to their layered structure and superior physical and chemical properties. The inclusion of graphene and metal oxides with other nanomaterials in electrodes have led to the significant enhancements in electrical conductivity, reaction kinetics, capacity, rate performance and accommodating the large volume change respectively. Moreover, these 2D materials facilitated large surface areas and shorter paths for sodium ion adsorption and transportation respectively. In this review article, the fabrication techniques, structural configuration, sodium ion storage mechanism and its electrochemical performances will be introduced. Subsequently, an insight into the recent advancements in SIBs associated with 2D anode materials (graphene, graphene oxide (GO), transition metal oxides etc.) and other graphene-like elementary analogues (germanene, stanine etc.) as anode materials respectively will be discussed. Finally, the key challenges and future perspectives of SIBs towards enhancing the sodium storage performance of graphene-based electrode materials are discussed. In summary, we believe that this review will shed light on the path towards achieving long-cycling life, low operation cost and safe SIBs with high energy density using 2D anode materials and to be suitably commercialized for large-scale energy storage applications in the future.

In Situ Construction of (NiCo)3Se4 Nanobeads Embedded in N-Doped Carbon 3D Interconnected Networks for Enhanced Sodium Storage

Transition metal selenides, boasting remarkable specific capacity, have emerged as a promising electrode material. However, the substantial volume fluctuations during sodium ion insertion and extraction result in inadequate cyclic stability and rate performance, impeding their practical utility. Here, we synthesized N-doped carbon three-dimensional (3D) interconnected networks encapsulating (NiCo)3Se4 nanoparticles, denoted as ((NiCo)3Se4/N-C), exhibiting a bead-like structure and carbon confinement through electrospinning and subsequent thermal treatment. The N-doped carbon 3D interconnected networks possess high porosity and ample volume buffering capacity, enhance conductivity, shorten ion diffusion paths, and mitigate mechanical stress induced by volume changes during cycling. The uniformly distributed (NiCo)3Se4 nanoparticles, featuring a stable structure, demonstrate rapid electrochemical kinetics and numerous available active sites. The distinctive structure and composition of the optimized (NiCo)3Se4/N-C material showcase a high specific capacity (656.2 mAh g-1 at 0.1 A g-1) and an outstanding rate capability. A kinetic analysis confirms that (NiCo)3Se4/N-C stimulates the pseudocapacitive Na+ storage mechanism with capacitance contributing up to 89.2% of the total capacity. This unique structure design and doping approach provide new insights into the design of electrode materials for high-performance batteries.

Enhanced redox kinetics in hierarchical tubular FeSe2 by incorporating Se quantum dots towards high-performance sodium-ion batteries

Metal selenides have emerged as promising Na-storage anode materials owing to their substantial theoretical capacity and high cost-effectiveness. However, the application of metal selenides is hindered by inferior electronic conductivity, huge volume variation, and sluggish kinetics of ionic migration. In response to these challenges, herein, a hierarchical hollow tube consisting of FeSe2 nanosheets and Se quantum dots anchored within a carbon skeleton (HT-FeSe2/Se/C) is strategically engineered and synthesized. The most remarkable feature of HT-FeSe2/Se/C is the introduction of Se quantum dots, which could lead to high electron density near the Fermi level and significantly enhance the overall charge transfer capability of the electrode. Moreover, the distinctive hollow tubular structure enveloped by the carbon skeleton endows the HT-FeSe2/Se/C anode with robust structural stability and fast surface-controlled Na-storage kinetics. Consequently, the as-synthesized HT-FeSe2/Se/C demonstrates a reversible capacity of 253.5 mAh/g at a current density of 5 A/g and a high specific capacity of 343.9 mAh/g at 1 A/g after 100 cycles in sodium-ion batteries (SIBs). Furthermore, a full cell is assembled with HT-FeSe2/Se/C as the anode, and a vanadium-based cathode (Na3V2(PO4)2O2F), showcasing a high specific capacity of 118.1 mAh/g at 2 A/g. The excellent performance of HT-FeSe2/Se/C may hint at future material design strategies and advance the development and application of SIBs.

Strain Self-Adaptive Iron Selenides Toward Stable Na+-Ion Batteries with Impressive Initial Coulombic Efficiency

High tap density electrodes play a vital role in developing rechargeable batteries with high volumetric capacities, however, developing advanced electrodes with satisfied capacity, excellent structural stability, and achieving the resulted batteries with a high initial Coulombic efficiency (ICE) and good rate capability with long lifespan simultaneously, are still an intractable challenge. Herein, an ultrahigh ICE of 94.1% and stable cycling of carbon-free iron selenides anode is enabled with a high tap density of 2.57 g cm-3 up to 4000 cycles at 5 A g-1 through strain-modulating by constructing a homologous heterostructure. Systematical characterization and theoretical calculation show that the self-adaptive homologous heterointerface alleviates the stress of the iron selenide anodes during cycling processes and subsequently improves the stability of the assembled batteries. Additionally, the well-formed homologous heterostructure also contributes to the rapid Na+ diffusion kinetic, increased charge transfer, and good reversibility of the transformation reactions, endowing the appealing rate capability of carbon-free iron selenides. The proposed design strategy provides new insight and inspiration to aid in the ongoing quest for advanced electrode materials with high tap densities and excellent stability.

Dual engineering of hetero-interfaces and architecture in MoSe2/VSe1.6@NC nanoflower for fast and stable sodium/potassium storage

Rational structure design is significant for the selenide anodes in the sodium/potassium ion batteries (SIBs/PIBs). Herein, dual engineering of hetero-interfaces and architecture is proposed to design SIB/PIB anodes. Attributed to the coordination binding with Mo7O246- and VO3-, the polydopamine assembly is demonstrated as an ideal template to produce bimetallic selenide of MoSe2/VSe1.6 anchoring on the in-situ N-doped carbon matrix (MoSe2/VSe1.6@NC). This ingenious hierarchical nanoflower structure can shorten the Na+/K+ diffusion length, increase the electron conductivity and buffer the volume changes, which can promote Na+/K+ reaction kinetics and stabilize the cycling performance. Consequently, the sodium/ potassium storage performance of MoSe2/VSe1.6@NC can be boosted. In SIBs, it achieves a capacity of 202 mAh/g at 10.0 A/g for 5000 cycles. Meanwhile, stable capacities of 207.1 mAh/g can be reached at 1.0 A/g over 1000 cycles in the PIBs. Furthermore, impressive capacities of 222.1 mAh/g and 100.4 mAh/g are delivered in the full cells of MoSe2/VSe1.6@NC//Na3V2(PO4)3@C and MoSe2/VSe1.6@NC//FePBA, respectively. This proves the potential practical application for the MoSe2/VSe1.6@NC anode in SIBs/PIBs.

Se-p Orbitals Induced "Strong d-d Orbitals Interaction" Enable High Reversibility of Se-Rich ZnSe/MnSe@C Electrode as Excellent Host for Sodium-Ion Storage

The heterostructure of transition-metal chalcogenides is a promising approach to boost alkali ion storage due to fast charge kinetics and reduction of activation energy. However, cycling performance is a paramount challenge that is suffering from poor reversibility. Herein, it is reported that Se-rich particles can chemically interact with local hexagonal ZnSe/MnSe@C heterostructure environment, leading to effective ions insertion/extraction, enabling high reversibility. Enlightened by theoretical understanding, Se-rich particles endow high intrinsic conductivities in term of low energy barriers (1.32 eV) compared with those without Se-rich particles (1.50 eV) toward the sodiation process. Moreover, p orbitals of Se-rich particles may actively participate and further increase the electronegativity that pushes the Mn d orbitals (dxy and dx2-y2) and donate their electrons to dxz and dyz orbitals, manifesting strong d-d orbitals interaction between ZnSe and MnSe. Such fundamental interaction will adopt a well-stable conducive electronic bridge, eventually, charges are easily transferred from ZnSe to MnSe in the heterostructure during sodiation/desodiation. Therefore, the optimized Se-rich ZnSe/MnSe@C electrode delivered high capacity of 576 mAh g-1 at 0.1 A g-1 after 100 cycles and 384 mAh g-1 at 1 A g-1 after 2500 cycles, respectively. In situ and ex situ measurements further indicate the integrity and reversibility of the electrode materials upon charging/discharging.

Transition Metal Selenide-Based Anodes for Advanced Sodium-Ion Batteries: Electronic Structure Manipulation and Heterojunction Construction Aspect

In recent years, sodium-ion batteries (SIBs) have gained a foothold in specific applications related to lithium-ion batteries, thanks to continuous breakthroughs and innovations in materials by researchers. Commercial graphite anodes suffer from small interlayer spacing (0.334 nm), limited specific capacity (200 mAh g-1), and low discharge voltage (<0.1 V), making them inefficient for high-performance operation in SIBs. Hence, the current research focus is on seeking negative electrode materials that are compatible with the operation of SIBs. Many studies have been reported on the modification of transition metal selenides as anodes in SIBs, mainly targeting the issue of poor cycling life attributed to the volume expansion of the material during sodium-ion extraction and insertion processes. However, the intrinsic electronic structure of transition metal selenides also influences electron transport and sodium-ion diffusion. Therefore, modulating their electronic structure can fundamentally improve the electron affinity of transition metal selenides, thereby enhancing their rate performance in SIBs. This work provides a comprehensive review of recent strategies focusing on the modulation of electronic structures and the construction of heterogeneous structures for transition metal selenides. These strategies effectively enhance their performance metrics as electrodes in SIBs, including fast charging, stability, and first-cycle coulombic efficiency, thereby facilitating the development of high-performance SIBs.

Superlong cycle-life sodium-ion batteries supported by electrode/active material interaction and heteroatom doping: Mechanism and application

To achieve both the capacity and stability of metal sulfides simultaneously remains a significant challenge. In this study, we have synthesized the manganese-doped copper sulfide three-dimensional (3D) hollow flower-like sphere (M/CuS-NSC), encapsulated in a nitrogen and sulfur co-doped carbon. The hollow lamellae structure allows the rational self-aggregation process of numerous active surface area enlarged nanosheets, thereby enhancing electrochemical activity. The subsurface framework characterized by CSC bonds enhances the pseudo-capacitive properties. Furthermore, the transformation of sulfur and the isomerization of carbon contribute to the enhancement of sodium ion storage. The incorporation of Mn into CuS lattice increases the interplanar distance, providing additional space for the accommodation of sodium ions. Mn doping facilitates the localization of electrons near the Fermi level, thereby improving conductivity. Additionally, Cu foils coated with M/CuS-NSC-2 engage with the electrolyte and sulfur, initiating the reaction sequence through the formation of Cu9S8. Consequently, M/CuS-NSC-2 exhibits highly reversible capacities of 676.24 mAh g-1 after 100 cycles at 0.1 A g-1 and 511.52 mAh g-1 after 10000 cycles at 10 A g-1, with an average attenuation ratio of only 0.009 %. In this study, we propose an effective strategy that combines structural design with heteroatom doping, providing a novel approach to enhance the electrochemical performance of monometallic sulfide.

Designing 3D SnS@Cu-Ni Nanoporous Column Array Electrode for High-Capacity and High-Rate Lithium-Ion Batteries

Sn-based materials with high capacity showcase great potential for next-generation lithium-ion batteries (LIBs). Yet, the large volume change and limited ion/electron transfer efficiency of Sn-based materials upon operation significantly compromises the battery performance. In this study, a unique 3D copper-nickel nanoporous column array current collector is rationally developed via a facile template-free galvanostatic electrodeposition method, followed by electrodepositing SnS active material onto it (denoted as 3D SnS@CNCA). Excitingly, the morphology of the 3D SnS@CNCA electrode perfectly inherited the nanoporous column array structure of the 3D current collector, which not only endows the electrode with a large specific surface area to provide more active sites and sufficient ion/electron transport pathways, but also effectively alleviates the volume expansion of SnS upon repeated charge-discharge cycles. Therefore, the binder-free 3D SnS@CNCA electrode showcases a significantly enhanced Li storage performance, showing a high initial reversible capacity of 1019.7 mAh g-1 with noteworthy cycling stability (a capacity retention rate of 89.4% after 200 cycles). Moreover, the designed electrode also manifests high rate performance with a high capacity of 570.6 mAh g-1 at 4 A g-1. This work provides a novel design idea for the preparation of high-performance electrodes beyond LIBs.

Atomic-level modulation of electron density in iron sulfides for enhancing sodium storage kinetics

Iron sulfides (FeS2) are promising anode materials for sodium ion batteries (SIBs); however, their inferior electronic conductivity, large volume swelling, and sluggish sodium ion diffusion kinetics lead to unsatisfactory rate performance and cycling durability. Heteroatom doping plays a crucial role in modifying the physicochemical properties of FeS2 anodes to enhance its sodium storage. Herein, ultra-fine Ni-doped FeS2 nanocrystals derived from a metal-organic framework (MOF) and in-situ anchored on a nitrogen doped carbon skeleton (Ni-FeS2@NC) are proposed to enhance both structural stability and reaction kinetics. Material characterization, electrochemical performance, and kinetics analysis demonstrate the critical role of Ni doping in sodium storage, particularly in accelerating Na+ diffusion efficiency. The N-doped carbon derived from the MOF can buffer the volume expansion and enhance the structural stability of electrode materials during sodiation/desodiation processes. As expected, Ni-FeS2@NC exhibits a high reversible capacity of 656.6 ± 65.1 mAh g-1 at 1.0 A g-1 after 200 cycles, superior rate performance (308.8 ± 6.0 mAh g-1 at 10.0 A g-1), and long-term cycling durability over 2000 cycles at 1.0 A g-1. Overall, this study presents an effective approach for enhancing the sodium storage performance and kinetics of anode materials for high efficiency SIBs.

Deciphering the Performance Enhancement, Cell Failure Mechanism, and Amelioration Strategy of Sodium Storage in Metal Chalcogenides-Based Andes

Transition metal chalcogenides (TMCs) emerge as promising anode materials for sodium-ion batteries (SIBs), heralding a new era of energy storage solutions. Despite their potential, the mechanisms underlying their performance enhancement and susceptibility to failure in ether-based electrolytes remain elusive. This study delves into these aspects, employing CoS2 electrodes as a case in point to elucidate the phenomena. The investigation reveals that CoS2 undergoes a unique irreversible and progressive solid-liquid-solid phase transition from its native state to sodium polysulfides (NaPSs), and ultimately to a Cu1.8S/Co composite, accompanied by a gradual morphological transformation from microspheres to a stable 3D porous architecture. This reconstructed 3D porous structure is pivotal for its exceptional Na+ diffusion kinetics and resilience to cycling-induced stress, being the main reason for ultrastable cycling and ultrahigh rate capability. Nonetheless, the CoS2 electrode suffers from an inevitable cycle life termination due to the microshort-circuit induced by Na metal corrosion and separator degradation. Through a comparative analysis of various TMCs, a predictive framework linking electrode longevity is established to electrode potential and Gibbs free energy. Finally, the cell failure issue is significantly mitigated at a material level (graphene encapsulation) and cell level (polypropylene membrane incorporation) by alleviating the NaPSs shuttling and microshort-circuit.

Metal Phosphide Anodes in Sodium-Ion Batteries: Latest Applications and Progress

Sodium-ion batteries (SIBs), as the next-generation high-performance electrochemical energy storage devices, have attracted widespread attention due to their cost-effectiveness and wide geographical distribution of sodium. As a crucial component of the structure of SIBs, the anode material plays a crucial role in determining its electrochemical performance. Significantly, metal phosphide exhibits remarkable application prospects as an anode material for SIBs because of its low redox potential and high theoretical capacity. However, due to volume expansion limitations and other factors, the rate and cycling performance of metal phosphides have gradually declined. To address these challenges, various viable solutions have been explored. In this paper, the recent research progress of metal phosphide materials for SIBs is systematically reviewed, including the synthesis strategy of metal phosphide, the storage mechanism of sodium ions, and the application of metal phosphide in electrochemical aspects. In addition, future challenges and opportunities based on current developments are presented.

Structure regulation and synchrotron radiation investigation of cathode materials for aqueous Zn-ion batteries

In view of the advantages of low cost, environmental sustainability, and high safety, aqueous Zn-ion batteries (AZIBs) are widely expected to hold significant promise and increasingly infiltrate various applications in the near future. The development of AZIBs closely relates to the properties of cathode materials, which depend on their structures and corresponding dynamic evolution processes. Synchrotron radiation light sources, with their rich advanced experimental methods, serve as a comprehensive characterization platform capable of elucidating the intricate microstructure of cathode materials for AZIBs. In this review, we initially examine available cathode materials and discuss effective strategies for structural regulation to boost the storage capability of Zn2+. We then explore the synchrotron radiation techniques for investigating the microstructure of the designed materials, particularly through in situ synchrotron radiation techniques that can track the dynamic evolution process of the structures. Finally, the summary and future prospects for the further development of cathode materials of AZIBs and advanced synchrotron radiation techniques are discussed.

Electrochemical coupling in subnanometer pores/channels for rechargeable batteries

Subnanometer pores/channels (SNPCs) play crucial roles in regulating electrochemical redox reactions for rechargeable batteries. The delicately designed and tailored porous structure of SNPCs not only provides ample space for ion storage but also facilitates efficient ion diffusion within the electrodes in batteries, which can greatly improve the electrochemical performance. However, due to current technological limitations, it is challenging to synthesize and control the quality, storage, and transport of nanopores at the subnanometer scale, as well as to understand the relationship between SNPCs and performances. In this review, we systematically classify and summarize materials with SNPCs from a structural perspective, dividing them into one-dimensional (1D) SNPCs, two-dimensional (2D) SNPCs, and three-dimensional (3D) SNPCs. We also unveil the unique physicochemical properties of SNPCs and analyse electrochemical couplings in SNPCs for rechargeable batteries, including cathodes, anodes, electrolytes, and functional materials. Finally, we discuss the challenges that SNPCs may face in electrochemical reactions in batteries and propose future research directions.

Tailoring Na+ Solvation Environment and Electrode-Electrolyte Interphases with Sn(OTf)2 Additive in Non-flammable Phosphate Electrolytes towards Safe and Efficient Na-S Batteries

Room-temperature sodium-sulfur (RT Na-S) batteries are promising for low-cost and large-scale energy storage applications. However, these batteries are plagued by safety concerns due to the highly flammable nature of conventional electrolytes. Although non-flammable electrolytes eliminate the risk of fire, they often result in compromised battery performance due to poor compatibility with sodium metal anode and sulfur cathode. Herein, we develop an additive of tin trifluoromethanesulfonate (Sn(OTf)2 ) in non-flammable phosphate electrolytes to improve the cycling stability of RT Na-S batteries via modulating the Na+ solvation environment and interface chemistry. The additive reduces the Na+ desolvation energy and enhances the electrolyte stability. Moreover, it facilitates the construction of Na-Sn alloy-based anode solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI). These interphases help to suppress the growth of Na dendrites and the dissolution/shuttling of sodium polysulfides (NaPSs), resulting in improved reversible capacity. Specifically, the Na-S battery with the designed electrolyte boosts the capacity from 322 to 906 mAh g-1 at 0.5 A g-1 . This study provides valuable insights for the development of safe and high-performance electrolytes in RT Na-S batteries.

Stress Dissipation Driven by Multi-Interface Built-In Electric Fields and Desert-Rose-Like Structure for Ultrafast and Superior Long-Term Sodium Ion Storage

The kinetics and durability of conversion-based anodes greatly depend on the intrinsic stress regulating ability of the electrode materials, which has been significantly neglected. Herein, a stress dissipation strategy driven by multi-interface built-in electric fields (BEFs) and architected structure, is innovatively proposed to design ultrafast and long-term sodium ion storage anodes. Binary Mo/Fe sulfide heterostructured nanorods with multi-interface BEFs and staggered cantilever configuration are fabricated to prove our concept. Multi-physics simulations and experimental results confirm that the inner stress in multiple directions can be dissipated by the multi-interface BEFs at the micro-scale, and by the staggered cantilever structure at the macro-scale, respectively. As a result, our designed heterostructured nanorods anode exhibits superb rate capability (332.8 mAh g-1 at 10.0 A g-1 ) and durable cyclic stability over 900 cycles at 5.0 A g-1 , outperforming other metal chalcogenides. This proposed stress dissipation strategy offers a new insight for developing stable structures for conversion-based anodes.

Dual Design on Hierarchically Hollow MoTe2/C with Ion/Electron Channel Engineering for High-Performance Sodium Storage

Transition-metal tellurides have been investigated as novel anode materials for application in sodium-ion batteries (SIBs) due to their rich active sites and unique and controllable layered nanostructures. However, the weak structural strength and inferior intercalation/deintercalation kinetics inhibit the development of transition-metal tellurides. In this work, MoTe2/C composites with two different hollow nanostructures are designed and prepared. By adjustment of the precursor structure, MoTe2/C-2 exhibits superior sodium-storage performance because of its uniquely hollow nanostructure with self-assembled 2D flexible nanosheets grown on the external surface. MoTe2/C-2 delivers a higher specific capacity (276 mAh g-1 at 0.1 A g-1 after 300 cycles), much more than MoTe2/C-1 (201 mAh g-1 at 0.1 A g-1 after 300 cycles), and exhibits a long-time cycling performance (131 mAh g-1 at 1 A g-1 after 2000 cycles). The excellent sodium-storage performance derived from the rational structure design is beneficial for shortening the ion paths, facilitating the sodiation/desodiation process, and reinforcing the intrinsic structural stability, thus boosting the reaction kinetics and prolonging the cycling life. Meanwhile, the assembled full-cell maintains 101 mAh g-1 at 0.1 A g-1 after 50 cycles and lights an electric watch. The findings provide several new views for preparation of more transition-metal tellurides with multi-ion/electron migration channel engineering.

MOF-Derived Bimetallic Selenide CoNiSe2 Nanododecahedrons Encapsulated in Porous Carbon Matrix as Advanced Anodes for Lithium-Ion Batteries

Transition metal selenides have received considerable attention as promising candidates for lithium-ion battery (LIB) anode materials due to their high theoretical capacity and safety characteristics. However, their commercial viability is hampered by insufficient conductivity and volumetric fluctuations during cycling. To address these issues, we have utilized bimetallic metal-organic frameworks to fabricate CoNiSe2/C nanodecahedral composites with a high specific surface area, abundant pore structures, and a surface-coated layer of the carbon-based matrix. The optimized material, CoNiSe2/C-700, exhibited impressive Li+ storage performance with an initial discharge specific capacity of 2125.5 mA h g-1 at 0.1 A g-1 and a Coulombic efficiency of 98% over cycles. Even after 1000 cycles at 1.0 A g-1, a reversible discharge specific capacity of 549.9 mA h g-1 was achieved. The research highlights the synergistic effect of bimetallic selenides, well-defined nanodecahedral structures, stable carbon networks, and the formation of smaller particles during initial cycling, all of which contribute to improved electronic performance, reduced volume change, increased Li+ storage active sites, and shorter Li+ diffusion paths. In addition, the pseudocapacitance behavior contributes significantly to the high energy storage of Li+. These features facilitate rapid charge transfer and help maintain a stable solid-electrolyte interphase layer, which ultimately leads to an excellent electrochemical performance. This work provides a viable approach for fabricating bimetallic selenides as anode materials for high-performance LIBs through architectural engineering and compositional tailoring.

Amorphous MoS3-modified porous Co4S3-embedded N,S co-doped carbon polyhedron as new high-capacity and high-rate anode materials for sodium-ion half/full cells

In this study, amorphous MoS3-modified porous Co4S3-embedded N,S co-doped carbon polyhedron (Co4S3@NSC/MoS3) was rationally prepared via a multi-step method. One-dimensional linear-like MoS3 with a high specific capacity of 894 mAh g-1 and abundant active sites compensated for the low capacity of Co4S3, thus enhancing the sodium ion storage capacity of the entire electrode. Moreover, three-dimensional N,S co-doped carbon networks (NSC) significantly inhibited large volumetric fluctuations in Co4S3 and MoS3, thereby sustaining the structural stability and enhancing the electron transfer efficiency. As a new anode material for sodium-ion half batteries, the constructed Co4S3@NSC/MoS3 with rapid Na+ diffusion and charge transfer kinetics demonstrated better sodium storage properties than Co4S3@NSC. At a rate of 0.5 A g-1 over 100 cycles, the reversible specific capacity of Co4S3@NSC/MoS3 reached 594 mAh g-1. Even when cycled at a rate of 2 A g-1 for 600 cycles, the charge capacity was stable at 435 mAh g-1. The rate performance of Co4S3@NSC/MoS3 was also found to be remarkable; when the rate increased to 10 A g-1, the average capacity was retained at 382 mAh g-1. Apart from half cells, reduced graphene oxide (rGO)-modified Na3V2(PO4)3 composite (Na3V2(PO4)3@rGO) was used as the cathode material to match with Co4S3@NSC/MoS3. The assembled full batteries were analyzed and their electrochemical properties were discussed. They also exhibited outstanding rate capability and high-rate long-life cyclic property. Even at 1 A g-1 over 500 cycles, the discharge capacity was stably maintained at 246 mAh g-1. The outstanding sodium storage properties of Co4S3@NSC/MoS3 mainly depended on the cooperative effects of MoS3 and Co4S3@NSC, indicating the potential application of Co4S3@NSC/MoS3 in energy storage fields.

A Se-induced heterostructure electrode with polymetallic-CoNiFe towards high performance supercapacitors

Rational regulation of electrode materials with high conductivity and unexceptionable cycling stability is crucial to meet the requirements of high-performance supercapacitors (SCs). Herein, a hierarchical porous kebab-like heterostructure (CoNiFe-Se) is prepared by a facile solvothermal reaction and selenization step. Both experimental and computational results demonstrate that incorporating Se via hydrothermal reaction contributes to modulating the morphology and electronic structure of transition metal carbonate hydroxides. The heterostructured electrode with abundant active sites composed of electroactive polymetallic-CoNiFe imparts excellent charge storage. Additionally, the unique structure of CoNiFe-Se with its heterogeneous interface, oxygen vacancies and cavities improves electrochemical activity, accelerates electron transfer and suppresses the volume expansion during the cycling. As a result, the CoNiFe-Se exhibits excellent electrochemical performance of 5040 mF cm-2 at 1 mA cm-2 and long-term durability with 85.7% retained capacitance after 10 000 cycles. Interestingly, an integrated asymmetric supercapacitor performs well for energy storage. This finding opens a new avenue for developing transition metal carbonate hydroxides using selenization strategies in the field of SCs.

SiSe2 for Superior Sulfide Solid Electrolytes and Li-Ion Batteries

Among the various existing layered compounds, silicon diselenide (SiSe2) possesses diverse chemical and physical properties, owing to its large interlayer spacing and interesting atomic arrangements. Despite the unique properties of layered SiSe2, it has not yet been used in energy applications. Herein, we introduce the synthesis of layered SiSe2 through a facile solid-state synthetic route and demonstrate its versatility as a sulfide solid electrolyte (SE) additive for all-solid-state batteries (ASSBs) and as an anode material for Li-ion batteries (LIBs). Li-argyrodites with various compositions substituted with SiSe2 are synthesized and evaluated as sulfide SEs for ASSBs. SiSe2-substituted Li-argyrodites exhibit high ionic conductivities, low activation energies, and high air stabilities. In addition, when using a sulfide SE, the ASSB full cell exhibits a high discharge/charge capacity of 202/169 mAh g-1 with a high initial Coulombic efficiency (ICE) of 83.7% and stable capacity retention at 1C after 100 cycles. Furthermore, the Li-storage properties of SiSe2 as an anode material for LIBs are evaluated, and its Li-pathway mechanism is explored by using various cutting-edge ex situ analytical tools. Moreover, the SiSe2 nanocomposite anode exhibits a high Li- insertion/extraction capacity of 950/775 mAh g-1, a high ICE of 81.6%, a fast rate capability, and stable capacity retention after 300 cycles. Accordingly, layered SiSe2 and its versatile applications as a sulfide SE additive for ASSBs and an anode material for LIBs are promising candidates in energy storage applications as well as myriad other applications.

Inorganic All-Solid-State Sodium Batteries: Electrolyte Designing and Interface Engineering

Inorganic all-solid-state sodium batteries (IASSSBs) are emerged as promising candidates to replace commercial lithium-ion batteries in large-scale energy storage systems due to their potential advantages, such as abundant raw materials, robust safety, low price, high-energy density, favorable reliability and stability. Inorganic sodium solid electrolytes (ISSEs) are an indispensable component of IASSSBs, gaining significant attention. Herein, this review begins by discussing the fundamentals of ISSEs, including their ionic conductivity, mechanical property, chemical and electrochemical stabilities. It then presents the crystal structures of advanced ISSEs (e.g., β/β''-alumina, NASICON, sulfides, complex hydride and halide electrolytes) and the related issues, along with corresponding modification strategies. The review also outlines effective approaches for forming intimate interfaces between ISSEs and working electrodes. Finally, current challenges and critical perspectives for the potential developments and possible directions to improve interfacial contacts for future practical applications of ISSEs are highlighted. This comprehensive review aims to advance the understanding and development of next-generation rechargeable IASSSBs.

Co4S3 Nanoparticles Confined in an MnS Nanorod-Grafted N, S-Codoped Carbon Polyhedron for Highly Efficient Sodium-Ion Batteries

Sodium-ion batteries (SIBs) suffer from limited ion diffusion and structural expansion, generating the urgent demand for Na+ accommodable materials with promising architectures. In this work, the rational exploration for Co4S3 nanoparticles confined in an MnS nanorod-grafted N, S-codoped carbon polyhedron (Co-Mn-S@N-S-C) is achieved by the in situ growth of MOF on MnO2 nanorod along with the subsequent carbonization and sulfurization. Benefiting from the distinctive nanostructure, the Co-Mn-S@N-S-C anode delivers excellent structural stability, resulting in prolonged cycling stability with a capacity retention of 90.2% after 1000 cycles at 2 A g-1. Moreover, the reaction storage mechanism is clarified by the in situ X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The results indicate that properly designed electrode materials have huge potential applications for highly efficient energy storage devices.

A cobalt-doped hollow ZnS polyhedra@porous carbon shell composite anode for high-rate sodium-ion batteries

Transition metal sulfides (TMSs) have drawn promising attention due to their low cost and high theoretical capacity for sodium storage. However, the critical issues of TMSs with huge volume changes and lower ionic/electronic conductivity are the major challenges for their practical application in sodium-ion batteries. Herein, we constructed cobalt-doped ZnS encapsulated in an N-doped carbon shell (denoted as Co-ZnS@NC), which effectively alleviates the volume expansion and improves sodium storage performance. The mechanism analysis and ion diffusion kinetics analysis (GITT, EIS, and CV) prove the acceleration of Na+ diffusion by the built-in electric field and buffer carbon layer in the Co-ZnS@NC, optimizing the cycle life and rate capability. The as-prepared Co-ZnS@NC has a high reversible capacity of 456.8 mA h g-1 after 1000 cycles at 1.0 A g-1 and superior rate capability (368.8 mA h g-1 at 20.0 A g-1), with Na metal as the counter electrode. Moreover, the assembled full cell shows a high energy density of 214.4 W h kg-1. This work provides insight on heteroatom doping for optimizing the rate capability of TMS anodes.

Co quantum dots embedded in modified montmorillonite loaded with graphitized carbon as an ultra-stable anode material for sodium-ion battery

Carbonaceous materials are competitive anodes in sodium-ion batteries (SIBs) due to their advantages, such as low cost, abundant active sites, and porosity. However, this type of material still suffers from slow rate capability and low capacity, which greatly hinders its application. In this work, the biomass-derived carbon is optimized based on a layered montmorillonite (Mt) skeleton and the cobalt quantum dots (Co QDs). A three-dimensional (3D) combination, specifically a 3D flower-like structure, of 0D material (Co QDs) and a two-dimensional (2D) material (Mt) has been achieved. The optimization and local limited effects of the Co QDs on the electronic properties have been demonstrated by density functional theory (DFT). The metallic Co QDs and carbon could form a Mott-Schottky junction, enhancing the conductivity and Na+ adsorption. Due to the synergetic improvement of structure and conductivity, the stripped Mt embedded with Co QDs loaded with nitrogen doped carbon (FMt@Co-NC) shows ultra-stable cycle stability (99.12% retention after 10,000 cycles at 10 A/g). This is the first time that Mt has been employed in high performance SIBs, which incubates a grand blueprint for effectively utilizing similar inactive energy-storage materials, through a simple and reliable approach.

A TiSe monolayer as a superior anode for applications of Li/Na/K-ion batteries

Using density functional theory (DFT), we investigated the energy-storage capabilities of a two-dimensional TiSe monolayer for applications of the anode material of Li/Na/K-ion batteries. The TiSe monolayer showed high thermodynamic stability at 800 K according to ab initio molecular dynamics (AIMD) simulation. The ion-diffusion barrier was estimated to be 0.29/0.36/0.33 eV for Li/Na/K, respectively, indicating the high-rate capacity of this material. The theoretical specific capacity was 422.63 mA h g-1 for Li/Na/K, with an energy density of 1000.19, 802.30, and 802.41 mW h g-1, respectively. Fully charged TiSe was mechanically stable according to the calculated elastic constants. Our results show that the TiSe monolayer could be used as an excellent anode material for Li/Na/K-ion batteries.

Manipulating Molecular Structure to Trigger Ultrafast and Long-Life Potassium Storage of Fe0.4 Ni0.6 S Solid Solution

Currently, the main obstacle to the widespread utilization of metal chalcogenides (MSx ) as anode for potassium-ion batteries (PIBs) is their poor rate capability and inferior cycling stability as a result of the undesirable electrical conductivity and severe pulverization of the nanostructure during large K-ions intercalation-extraction processes. Herein, an ultrafast and long-life potassium storage of metal chalcogenide is rationally demonstrated by employing Fe0.4 Ni0.6 S solid-solution (FNS/C) through molecular structure engineering. Benefiting from improved electroactivity and intense interactions within the unique solid solution phase, the electrical conductivity and structure durability of Fe0.4 Ni0.6 S are vastly improved. As anticipated, the FNS/C electrode delivers superior rate properties (538.7 and 210.5 mAh g-1 at 0.1 and 10 A g-1 , respectively) and long-term cycle stability (180.8 mAh g-1 at 5 A g-1 after 2000 cycles with a capacity decay of 0.011% per cycle). Moreover, the potassium storage mechanisms of Fe0.4 Ni0.6 S solid solution are comprehensively revealed by several in situ characterizations and theoretical calculations. This innovative molecular structure engineering strategy opens avenues to achieve high-quality metal chalcogenides for future advanced PIBs.

Engineering CSFe Bond Confinement Effect to Stabilize Metallic-Phase Sulfide for High Power Density Sodium-Ion Batteries

Metallic-phase iron sulfide (e.g., Fe7 S8 ) is a promising candidate for high power density sodium storage anode due to the inherent metal electronic conductivity and unhindered sodium-ion diffusion kinetics. Nevertheless, long-cycle stability can not be achieved simultaneously while designing a fast-charging Fe7 S8 -based anode. Herein, Fe7 S8 encapsulated in carbon-sulfur bonds doped hollow carbon fibers (NHCFs-S-Fe7 S8 ) is designed and synthesized for sodium-ion storage. The NHCFs-S-Fe7 S8 including metallic-phase Fe7 S8 embrace higher electron specific conductivity, electrochemical reversibility, and fast sodium-ion diffusion. Moreover, the carbonaceous fibers with polar CSFe bonds of NHCFs-S-Fe7 S8 exhibit a fixed confinement effect for electrochemical conversion intermediates contributing to long cycle life. In conclusion, combined with theoretical study and experimental analysis, the multinomial optimized NHCFs-S-Fe7 S8 is demonstrated to integrate a suitable structure for higher capacity, fast charging, and longer cycle life. The full cell shows a power density of 1639.6 W kg-1 and an energy density of 204.5 Wh kg-1 , respectively, over 120 long cycles of stability at 1.1 A g-1 . The underlying mechanism of metal sulfide structure engineering is revealed by in-depth analysis, which provides constructive guidance for designing the next generation of durable high-power density sodium storage anodes.

Three-Dimensional (3D) Ordered Macroporous Bimetallic (Mn,Fe) Selenide/Carbon Composite with Heterojunction Interface for High-Performance Sodium Ion Batteries

Transition-metal selenides have captured significant research attention as anode materials for sodium ion batteries (SIBs) due to their high theoretical specific capacities and excellent electronic conductivity. However, volumetric expansion and inferior cycle life still hinder their practical application. Herein, a three-dimensional (3D) ordered macroporous bimetallic (Mn,Fe) selenide modified by a carbon layer (denoted as 3DOM-MnFeSex@C) composite containing a heterojunction interface is fabricated through selenizing a 3D ordered macroporous Mn-based Prussian Blue analogue single crystal. The 3DOM-MnFeSex@C exhibits hierarchically porous architecture with enhanced mass-transfer efficiency; MnSe and FeSe2 particles are encapsulated into macroporous carbon framework, which can significantly promote the electronic conductivity and maintain the structural integrity. The density functional theory calculation indicates that the heterojunction interface between MnSe and FeSe2 has been successfully engineered so that Na+ can be readily adsorbed and rapidly converted, thus promoting the reaction kinetics and extending the cyclic life. As expected, the 3DOM-MnFeSex@C composite delivers excellent rate performance (277.6 mA h g-1 at 10 A g-1), and prolonged cycling life (191.6 mA h g-1 even after 1000 cycles at 2 A g-1) as a sodium storage anode. The sodium storage mechanism of the composite was further investigated by in situ X-ray diffraction and ex situ high-resolution transmission electron microscopy characterization techniques.

A NiS2/C composite as an innovative anode material for sodium-ion batteries: ex situ XANES and EXAFS studies to investigate the sodium storage mechanism

The successful deployment of sodium-ion batteries (SIBs) requires high-performance sustainable and cost-effective anode materials having a high current density. In this regard, sodium disulphide (NiS2) has been prepared as a composite with activated carbon (C) using a facile hydrothermal synthesis route in the past. The X-ray diffraction pattern of the as-prepared NiS2/C composite material shows well-defined diffraction peaks of NiS2. Most carbonaceous materials are amorphous, and the Brunauer-Emmett-Teller (BET) study shows that the surface area is close to 148 m2 g-1. At a current density of 50 mA g-1, the NiS2/C composite exhibits a high capacity of 480 mA h g-1 during the initial cycle, which subsequently decreases to 333 mA h g-1 after the completion of the 100th cycle. The NiS2/C composite electrode provides an exceptional rate capability by delivering a capacity of 270 mA h g-1 at a high current density of 2000 mA g-1, suggesting the suitability of the NiS2/C composite for SIBs. Ex situ X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses at the Ni K-edge have been used to examine the type of chemical bonding present in the anode and also how it changes during electrochemical redox cycling. The understanding of the sodium storage mechanism is improved by the favorable results, which also offer insights for developing high-performance electrode materials for rechargeable SIBs.

Recent progress and strategic perspectives of inorganic solid electrolytes: fundamentals, modifications, and applications in sodium metal batteries

Solid-state electrolytes (SEs) have attracted overwhelming attention as a promising alternative to traditional organic liquid electrolytes (OLEs) for high-energy-density sodium-metal batteries (SMBs), owing to their intrinsic incombustibility, wider electrochemical stability window (ESW), and better thermal stability. Among various kinds of SEs, inorganic solid-state electrolytes (ISEs) stand out because of their high ionic conductivity, excellent oxidative stability, and good mechanical strength, rendering potential utilization in safe and dendrite-free SMBs at room temperature. However, the development of Na-ion ISEs still remains challenging, that a perfect solution has yet to be achieved. Herein, we provide a comprehensive and in-depth inspection of the state-of-the-art ISEs, aiming at revealing the underlying Na⁺ conduction mechanisms at different length scales, and interpreting their compatibility with the Na metal anode from multiple aspects. A thorough material screening will include nearly all ISEs developed to date, i.e., oxides, chalcogenides, halides, antiperovskites, and borohydrides, followed by an overview of the modification strategies for enhancing their ionic conductivity and interfacial compatibility with Na metal, including synthesis, doping and interfacial engineering. By discussing the remaining challenges in ISE research, we propose rational and strategic perspectives that can serve as guidelines for future development of desirable ISEs and practical implementation of high-performance SMBs.

Copper removal and recovery from electroplating effluent with wide pH ranges through hybrid capacitive deionization using CuSe electrode

In modern industry, selective extraction and recovery of Cu from strongly acidic electroplating effluent are crucial to reduce carbon emissions, alleviate resource scarcity, and mitigate water pollution, yielding considerable economic and environmental benefits. This study proposed a high-efficiency CuSe electrode to selectively remove Cu from electroplating effluent via hybrid capacitive deionization (HCDI). The potential of this electrode was thoroughly evaluated to assess its effectiveness. The CuSe electrode exhibited superior deionization performance in terms of Cu adsorption capacity, selectivity, and applicability in various water matrices. Specifically, under strong acid conditions (1 M H⁺), the CuSe electrode maintained an optimal adsorption capacity of 357.36 mg g^-1 toward Cu²⁺. In systems containing salt ions, heavy metals, and actual electroplating wastewater, the CuSe electrode achieved a remarkable removal efficiency of up to 90% for Cu²⁺ with a high distribution coefficient K_d. Notably, the capacitive deionization (CDI) system demonstrated the simultaneous removal of Cu-EDTA. The removal mechanism was further revealed using ex-situ X-ray diffraction and X-ray photoelectron spectroscopy analyses. Overall, this study presents a practical approach that extends the capabilities of CDI platforms for effectively removing and recovering Cu from acidic electroplating effluent.

Designing Sphere-like FeSe2-Carbon Composites with Rational Construction of Interfacial Traits towards Considerable Sodium-storage Capabilities

Due to their low cost and high stability, sodium-ion batteries have been increasingly studied. However, their further development is limited by the relative energy density, resulting in the search for high-capacity anodes. FeSe₂ displays high conductivity and capacity but still suffers from sluggish kinetics and serious volume expansion. Herein, through sacrificial template methods, a series of sphere-like FeSe₂-carbon composites are successfully prepared, displaying uniform carbon coatings and interfacial chemical FeOC bonds. Moreover, benefiting from the unique traits of precursor and acid treatment, rich structural voids are prepared, effectively alleviating volume expansion. Utilized as anodes of sodium-ion batteries, the optimized sample displays considerable capacity, achieving 462.9 mAh g^-1, with 88.75% coulombic efficiency at 1.0 A g^-1. Even at 5.0 A g^-1, their capacity can be kept at approximately 318.8 mAh g^-1, while the stable cycling can be prolonged to 200 cycles above. Supported by the detailed kinetic analysis, it can be noted that the existing chemical bonds facilitate the fast shuttling of ions at the interface, and the enhanced surface/near-surface properties are further vitrified. Given this, the work is expected to offer valuable insights for the rational design of metal-based samples toward advanced sodium-storage materials.

Synthesis of F-doped materials and applications in catalysis and rechargeable batteries

Elemental doping is one of the most essential techniques for material modification. It is well known that fluorine is considered to be a highly efficient and inexpensive dopant in the field of materials. Fluorine is one of the most reactive elements with the highest electronegativity (χ = 3.98). Compared to cationic doping, anionic doping is another valuable method for improving the properties of materials. Many materials have physicochemical limitations that affect their practical application in the field of catalysis and rechargeable ion batteries. Many researchers have demonstrated that F-doping can significantly improve the performance of materials for practical applications. This paper reviews the applications of various F-doped materials in photocatalysis, electrocatalysis, lithium-ion batteries, and sodium-ion batteries, as well as briefly introducing their preparation methods and mechanisms to provide researchers with more ideas and options for material modification.

Multicomponent Metal Oxide- and Metal Hydroxide-Based Electrocatalysts for Alkaline Water Splitting

Developing cost-effective, highly catalytic active, and stable electrocatalysts in alkaline electrolytes is important for the development of highly efficient anion-exchange membrane water electrolysis (AEMWE). To this end, metal oxides/hydroxides have attracted wide research interest for efficient electrocatalysts in water splitting owing to their abundance and tunable electronic properties. It is very challenging to achieve an efficient overall catalytic performance based on single metal oxide/hydroxide-based electrocatalysts due to low charge mobilities and limited stability. This review is mainly focused on the advanced strategies to synthesize the multicomponent metal oxide/hydroxide-based materials that include nanostructure engineering, heterointerface engineering, single-atom catalysts, and chemical modification. The state of the art of metal oxide/hydroxide-based heterostructures with various architectures is extensively discussed. Finally, this review provides the fundamental challenges and perspectives regarding the potential future direction of multicomponent metal oxide/hydroxide-based electrocatalysts.

Electrolyte Engineering on Performance Enhancement of NiCo2 S4 Anode for Sodium Storage

NiCo₂ S₄ is an attractive anode for sodium-ion batteries (SIBs) due to its high capacity and excellent redox reversibility. Practical deployment of NiCo₂ S₄ electrode in SIBs, however, is still hindered by the inferior capacity and unsatisfactory cycling performance, which result from the mismatch between the electrolyte chemistry and electrode. Herein, a functional electrolyte containing 1.0 m NaCF₃ SO₃ in diethylene glycol dimethyl ether (DEGDME) (1.0 m NaCF₃ SO₃ -DEGDME) is developed, which can be readily used for NiCo₂ S₄ anode with high initial coulomb efficiency (96.2%), enhanced cycling performance, and boosted capacities (341.7 mA h g^-1 after 250 continuous cycles at the current density of 200 mA g^-1 ). The electrochemical tests and related phase characterization combined with density functional theory (DFT) calculation indicate the ether-based electrolyte is more suitable for the NiCo₂ S₄ anode in SIBs due to the formation of a stable electrode-electrolyte interface. Additionally, the importance of the voltage window is also demonstrated to further optimize the electrochemical performance of the NiCo₂ S₄ electrode. The formation of sulfide intermediates during charging and discharging is predicted by combining DFT and verified by in situ XRD and HRTEM. The findings indicate that electrolyte engineering would be an effective way of performance enhancement for sulfides in practical SIBs.

Synergistically Achieving Superior Sodium Storage of Metal Selenides by Constructing N-Doped Carbon Foams and Utilizing Cu-Driven Replacement Reaction

Metal selenides are considered as one of the most promising anode materials for Na-ion batteries owing to high specific capacity and relatively higher electronic conductivity compared with metal sulfides or oxides. However, such anodes still suffer from huge volume change upon repeated Na⁺ insertion/extraction processes and simultaneously undergo severe shuttle effect of polyselenides, thus leading to poor electrochemical performance. Herein, a facile chemical-blowing and selenization strategy to fabricate 3D interconnected hybrids built from metal selenides (MSe, M = Mn, Co, Cr, Fe, In, Ni, Zn) nanoparticles encapsulated in in situ formed N-doped carbon foams (NCFs) is reported. Such hybrids not only provide ultrasmall active nanobuilding blocks (≈15 nm), but also efficiently anchor them inside the conductive NCFs, thus enabling both high-efficiency utilization of active components and high structural stability. On the other hand, Cu-driven replacement reaction is utilized for efficiently inhibiting the shuttle effect of polyselenides in ether-based electrolyte. Benefiting from the combined merits of the unique MSe@NCFs and the utilization of the conversion of metal selenides to copper selenides, the as-obtained hybrids (MnSe as an example) exhibit superior rate capability (386.6 mAh g^-1 up to 8 A g^-1 ) and excellent cycling stability (347.7 mAh g^-1 at 4.0 A g^-1 after 1200 cycles).

CoSe2 nanoparticles anchored on porous carbon network structure for efficient Na-ion storage

Cobalt selenide, as a star material in battery industry, has attracted much attention. However, when it is applied solely in sodium ion batteries, it will cause large volume expansion and material agglomeration, which will seriously affect the overall performance of batteries. In this work, we use ice bath impregnation to combine CoSe₂ nanoparticles with porous nitrogen-doped carbon networks (NC) as advanced anodes for ultra-long cycle life sodium ion batteries (SIBs). CoSe₂ nanoparticles are evenly attached to NC with strong interfacial contacts in CoSe₂@NC. The strong contact of CoSe₂ on the porous carbon network, along with the carbon network's unique network cross-linking structure, results in rapid electron transfer and Na ion diffusion kinetics of CoSe₂@NC, resulting in superior electrochemical performance. Besides, we have synthesized CoSe₂@NC with different loading by changing Co²⁺ concentration. The results show that CoSe₂@NC anode thus provides a high reversible capacity of 406 mAh/g. In addition, at high current 5 A/g, it can keep a reversible capacity of 300 mAh/g after 4500 cycles with an average capacity loss of less than 0.01 % per cycle. The excellent anchoring structure enables it to form stable solid electrolyte film (SEI) and reduce the amount of dead sodium in the first charge-discharge process, showing high Initial Coulombic Efficiency (ICE) (89.2 %). Finally, CoSe₂@NC and Na₃V₂(PO₄)₃ (NVP) are assembled into a full cell and the results shows an ultra-long cycle stability at 0.1 A/g. This strategy will facilitate the application of transition metal selenides in next-generation energy storage systems.

CuSe2 Nanocubes Enabling Efficient Sodium Storage

As the most promising candidate for lithium-ion batteries (LIBs), the electrochemical performance of sodium-ion batteries (SIBs) is highly dependent on the electrode materials. Copper selenides have established themselves as potential anode materials for SIBs due to their high theoretical capacity and good conductivity. However, the poor rate performance and fast capacity fading are the major challenges to their practical application in SIBs. Herein, single-crystalline CuSe₂ nanocubes (CuSe₂ NCs) are successfully synthesized via a solvothermal method. As an anode of SIBs, the CuSe₂ NCs render an almost 100% initial Coulombic efficiency, an outstanding long cycle life, e.g., 380 mA h g^-1 after 1700 cycles at 10 A g^-1, and an unprecedented rate performance of 344 mA h g^-1 at 50 A g^-1. Ex situ X-ray diffraction (XRD) patterns reveal the crystalline transformation of energy-storage materials, and the density functional theory (DFT) conclusion suggests that fast and stable ion diffusion kinetics enhances their electrochemical performance upon sodiation/desodiaton. The investigation into the mechanism provides a theoretical basis for subsequent practical applications.

Interface Modulation of Metal Sulfide Anodes for Long-Cycle-Life Sodium-Ion Batteries

Although studies of transition metal sulfides (TMS) as anode materials for sodium-ion batteries are extensively reported, the short cycle life is still a thorny problem that impedes their practical application. In this work, a new capacity fading mechanism of the TMS electrodes is demonstrated; that is, the parasitic reaction between electrolyte anions (i.e., ClO₄ ^- ) and metal sulfides yields non-conductive and unstable solid-electrolyte interphase (SEI) and meanwhile, corrosively turns metal sulfides into less-active oxides. This knowledge guides the development of an electrochemical strategy to manipulate the anion decomposition and construct a stable interface that prevents extensive parasitic reactions. It is shown that introducing sodium nitrate to the electrolyte radically changes the Na⁺ solvation structure by populating nitrate ions in the first solvation sheath, generating a stable and conductive SEI layer containing both Na₃ N and NaF. The optimized interface enables an iron sulfide anode to stably cycle for over 2000 cycles with negligible capacity loss, and a similar enhancement in cycle performance is demonstrated on a number of other metal sulfides. This work discloses metal sulfides' cycling failure mechanism from a unique perspective and highlights the critical importance of manipulating the interface chemistry in sodium-ion batteries.