SnS2 Nanosheets Coating on Nanohollow Cubic CoS2 /C for Ultralong Life and High Rate Capability Half/Full Sodium-Ion Batteries

Metal-Organic Framework-Based Materials for Advanced Sodium Storage: Development and Anticipation

As a pioneering battery technology, even though sodium-ion batteries (SIBs) are safe, non-flammable, and capable of exhibiting better temperature endurance performance than lithium-ion batteries (LIBs), because of lower energy density and larger ionic size, they are not amicable for large-scale applications. Generally, the electrochemical storage performance of a secondary battery can be improved by monitoring the composition and morphology of electrode materials. Because more is the intricacy of a nanostructured composite electrode material, more electrochemical storage applications would be expected. Despite the conventional methods suitable for practical production, the synthesis of metal-organic frameworks (MOFs) would offer enormous opportunities for next-generation battery applications by delicately systematizing the structure and composition at the molecular level to store sodium ions with larger sizes compared with lithium ions. Here, the review comprehensively discusses the progress of nanostructured MOFs and their derivatives applied as negative and positive electrode materials for effective sodium storage in SIBs. The commercialization goal has prompted the development of MOFs and their derivatives as electrode materials, before which the synthesis and mechanism for MOF-based SIB electrodes with improved sodium storage performance are systematically discussed. Finally, the existing challenges, possible perspectives, and future opportunities will be anticipated.

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

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

Achieving High Performance Electrode for Energy Storage with Advanced Prussian Blue-Drived Nanocomposites-A Review

Recently, Prussian blue analogues (PBAs)-based anode materials (oxides, sulfides, selenides, phosphides, borides, and carbides) have been extensively investigated in the field of energy conversion and storage. This is due to PBAs' unique properties, including high theoretical specific capacity, environmental friendly, and low cost. We thoroughly discussed the formation of PBAs in conjunction with other materials. The performance of composite materials improves the electrochemical performance of its energy storage materials. Furthermore, new insights are provided for the manufacture of low-cost, high-capacity, and long-life battery materials in order to solve the difficulties in different electrode materials, combined with advanced manufacturing technology and principles. Finally, PBAs and their composites' future challenges and opportunities are discussed.

High-Performance Lithium-Ion Storage of FeTiO3 with Morphology Adjustment and Niobium Doping

Ferrous titanate (FeTiO₃) has a high theoretical capacity and physical and chemical properties stability, so it is a potential lithium anode material. In this study, FeTiO₃ nanopowder and nanosheets were prepared by the sol-gel method and the hydrothermal method. In addition, niobium-ion doping was carried out, the radius of Nb close to Ti so the Nb can easily enter into the FeTiO₃ lattice. Nb can provide more free electrons to improve the electrochemical performance. Then, the effects of the morphology and niobium doping on the microstructure and electrochemical properties of FeTiO₃ were systematically studied. The results show that FeTiO₃ nanosheets have a better lithium storage performance than nanopowders because of its high specific surface area. A certain amount of niobium doping can improve the electrochemical performance of FeTiO₃. Finally, a 1 mol% niobium-doping FeTiO₃ nanosheets (1Nb-FTO-S) electrode provided a higher specific capacity of 782.1 mAh g^-1 at 50 mA g^-1. After 200 cycles, the specific capacity of the 1Nb-FTO-S electrode remained at 509.6 mAh g^-1. It is revealed that an increased specific surface area and ion doping are effective means to change the performance of lithium, and the proposed method looks promising for the design of other inorganic oxide electrode materials.

Moderate Specific Surface Areas Help Three-Dimensional Frameworks Achieve Dendrite-Free Potassium-Metal Anodes

The inevitable problem of dendrites growth has hampered the further development of K metal anodes. Constructing a three-dimensional anode framework and potassiophilic nanocoating is an effective way to enlarge the specific surface area, reduce the local current density, and inhibit the formation of K dendrites. However, the effects of the electrochemically active surface area (ECSA) of the framework on deposition behavior have not been clarified. Hence, SnS₂ nanosheets with different sizes are loaded on the surface of carbon paper (SnS₂@CP) to improve the potassiophilicity and realize dendrite-free K-metal anodes. Experiments reveal that the size of SnS₂ nanosheets would determine the ECSA of the framework, while the ECSA reveals the relative sizes of specific surface areas of frameworks. Excessive or limited specific surface areas will cause morphological collapse or weak potassiophilicity during potassiation, respectively, thus leading to high nucleation overpotential. The moderate specific surface area and abundant and stable potassiophilic sites prompt the SnS₂@CP framework to achieve uniform electrodeposition of K. A low nucleation overpotential of 11.2 mV and a cycle life of more than 800 h are exhibited at a current density of 0.25 mA cm^-2, indicating the directional strategy for stable and safe K metal anodes.

Bismuth Nanoparticles Anchored on Ti3 C2 Tx MXene Nanosheets for High-Performance Sodium-Ion Batteries

Sodium-ion batteries are promising energy-storage systems, but they are facing huge challenges for developing fast-charging anode materials. Bismuth (Bi)-based anode materials are considered as candidates for fast-charging anodes of sodium-ion batteries due to their excellent rate performance. Herein, we designed a two-dimensional Bi/MXene anode material based on a hydrogen thermal reduction strategy. Benefitting from microstructure advantages, Bi/MXene anodes exhibited an excellent rate capability and superior cycle performance in Na//Bi/MXene half-batteries and Na₃ V₂ (PO₄ )₃ /C//Bi/MXene full-batteries. Moreover, full-batteries can complete a charge/discharge cycle in 7 min and maintain an excellent cycle life (over 7000 cycles). The electrochemical test results showed that Bi/MXene is a promising anode material with fast charge/discharge capability for sodium-ion batteries.

Realizing Spherical Lithium Deposition by In Situ Formation of a Li2S/Li-Sn Alloy Mixed Layer on Carbon Paper for Stable and Safe Li Metal Anodes

Uncontrollable formation of Li dendrites and volume expansion have always been serious obstacles to the practical application of Li metal anodes. Three-dimensional (3D) frameworks are proven to accommodate Li to suppress volume expansion, but the lithiophobic surface tends to cause uncontrollable formation of Li dendrites. Here, uniform SnS₂ nanosheets are coated on the carbon paper (SnS₂@CP) skeleton and then transformed into a mixed layer of Li₂S/Li-Sn after lithiation. Under the joint action of the lithiophilic Li-Sn alloy and low-diffusion energy barrier Li₂S, the dual effects of strong adsorption and rapid diffusion of Li are realized. As a result, Li deposits homogeneously within the whole framework; as the plating amount increases, dendrite-free spherical Li is demonstrated, and the thickness of the electrode stays almost unchanged even at a high areal capacity of 10 mA h cm^-2. The SnS₂@CP electrodes present an ultralow nucleation overpotential (ca. 4 mV), high Coulombic efficiency (above 96.6% for more than 450 cycles), and stable cycle life (>1500 h), indicating that the 3D framework with the Li₂S/Li-Sn alloy mixed coating has excellent lithiophilicity and fast Li transport kinetics, thus effectively inhibiting the formation of Li dendrites. All the findings give new insights into the design strategy for stable and safe Li metal anodes.

SnSe2 /FeSe2 Nanocubes Capsulated in Nitrogen-Doped Carbon Realizing Stable Sodium-Ion Storage at Ultrahigh Rate

Metal selenides have attracted increasing attention recently as anodes for sodium-ion batteries (SIBs) because of their large capacities, high electric conductivity, as well as environmental benignity. However, the application of metal selenides is hindered by the huge volume variation, which causes electrode structure devastation and the consequent degrading cycling stability and rate capability. To overcome the aforementioned obstacles, herein, SnSe₂ /FeSe₂ nanocubes capsulated in nitrogen-doped carbon (SFS@NC) are fabricated via a facile co-precipitation method, followed by poly-dopamine wrapping and one-step selenization/carbonization procedure. The most remarkable feature of SFS@NC is the ultra-stability under high current density while delivering a large capacity. The synergistic effect of dual selenide components and core-shell architecture mitigates the volume effect, alleviates the agglomeration of nanoparticles, and further improves the electric conductivity. The as-prepared SFS@NC nanocubes present a high capacity of 408.1 mAh g^-1 after 1200 cycles at 6 A g^-1 , corresponding to an 85.3% retention, and can achieve a capacity of 345.0 mAh g^-1 at an extremely high current density of 20 A g^-1 . The outstanding performance of SFS@NC may provide a hint to future material structure design strategy, and promote further developments and applications of SIBs.

Conversion-Alloying Anode Materials for Sodium Ion Batteries

The past decade has witnessed a rapidly growing interest toward sodium ion battery (SIB) for large-scale energy storage in view of the abundance and easy accessibility of sodium resources. Key to addressing the remaining challenges and setbacks and to translate lab science into commercializable products is the development of high-performance anode materials. Anode materials featuring combined conversion and alloying mechanisms are one of the most attractive candidates, due to their high theoretical capacities and relatively low working voltages. The current understanding of sodium-storage mechanisms in conversion-alloying anode materials is presented here. The challenges faced by these materials in SIBs, and the corresponding improvement strategies, are comprehensively discussed in correlation with the resulting electrochemical behavior. Finally, with the guidance and perspectives, a roadmap toward the development of advanced conversion-alloying materials for commercializable SIBs is created.

Electrolyte/Structure-Dependent Cocktail Mediation Enabling High-Rate/Low-Plateau Metal Sulfide Anodes for Sodium Storage

As promising anodes for sodium-ion batteries, metal sulfides ubiquitously suffer from low-rate and high-plateau issues, greatly hindering their application in full-cells. Herein, exemplifying carbon nanotubes (CNTs)-stringed metal sulfides superstructure (CSC) assembled by nano-dispersed SnS₂ and CoS₂ phases, cocktail mediation effect similar to that of high-entropy materials is initially studied in ether-based electrolyte to solve the challenges. The high nano-dispersity of metal sulfides in CSC anode underlies the cocktail-like mediation effect, enabling the circumvention of intrinsic drawbacks of different metal sulfides. By utilizing ether-based electrolyte, the reversibility of metal sulfides is greatly improved, sustaining a long-life effectivity of cocktail-like mediation. As such, CSC effectively overcomes low-rate flaw of SnS₂ and high-plateau demerit of CoS₂, simultaneously realizes a high rate and a low plateau. In half-cells, CSC delivers an ultrahigh-rate capability of 327.6 mAh g^-1_anode at 20 A g^-1, far outperforming those of monometallic sulfides (SnS₂, CoS₂) and their mixtures. Compared with CoS₂ phase and SnS₂/CoS₂ mixture, CSC shows remarkably lowered average charge voltage up to ca. 0.62 V. As-assembled CSC//Na_1.5VPO_4.8F_0.7 full-cell shows a good rate capability (0.05 ~ 1.0 A g^-1, 120.3 mAh g^-1_electrode at 0.05 A g^-1) and a high average discharge voltage up to 2.57 V, comparable to full-cells with alloy-type anodes. Kinetics analysis verifies that the cocktail-like mediation effect largely boosts the charge transfer and ionic diffusion in CSC, compared with single phase and mixed phases. Further mechanism study reveals that alternative and complementary electrochemical processes between nano-dispersed SnS₂ and CoS₂ phases are responsible for the lowered charge voltage of CSC. This electrolyte/structure-dependent cocktail-like mediation effect effectively enhances the practicability of metal sulfide anodes, which will boost the development of high-rate/-voltage sodium-ion full batteries.

Synthesis and Applications of Nanostructured Hollow Transition Metal Chalcogenides

Nanostructures with well-defined structures and rich active sites occupy an important position for efficient energy storage and conversion. Recent studies have shown that a transition metal chalcogenide (TMC) has a unique structure, such as diverse structural morphology, excellent stability, high efficiency, etc., and is used in the fields of electrochemistry and catalysis. The nanohollow structure metal chalcogenide has broad application prospects due to the existence of a large number of active sites and a wide internal space, allowing a large number of ions and electrons to be transported. Summarizing synthetic strategies of nanostructured hollow transition metal sulfides (HTMC) and their applications in the field of energy storage and conversion is discussed here. Through some representative examples, the fabrication and properties of various hollow structures are analyzed, which prompt some emerging nanoengineering designs to be applied to transition metal chalcogenides. It is hoped that the construction of the HTMC will lead to a deeper understanding for the further exploration of energy storage and conversion.

Carbon nanotubes coupled with layered graphite to support SnTe nanodots as high-rate and ultra-stable lithium-ion battery anodes

SnTe exhibits a layered crystal structure, which enables fast Li-ion diffusion and easy storage, and is considered to be a promising candidate for an advanced anode material. However, its applications are hindered by the large volume variation caused by intercalation/deintercalation during the electrochemical reaction processes. Herein, topological insulator SnTe and carbon nanotubes (CNTs) supported on a graphite (G) carbon framework (SnTe-CNT-G) were prepared as a new, active and robust anode material for high-rate lithium-ion batteries by a scalable ball-milling method. Remarkably, the SnTe-CNT-G composite used as a lithium-ion battery anode offered an excellent reversible capacity of 840 mA h g-1 at 200 mA g-1 after 100 cycles and high initial coulombic efficiencies of 76.0%, and achieved a long-term cycling stability of 669 mA h g-1 at 2 A g-1 after 1400 cycles. The superior electrochemical performance of SnTe-CNT-G is attributed to the stable design of its electrode structure and interesting topological transition of SnTe, combined with multistep conversion and alloying processes. Furthermore, in situ X-ray diffraction and ex situ X-ray photoelectron spectroscopy were employed to study the reaction mechanism. The results presented here provide new insights to design and reveal the reaction mechanisms of transition metal telluride materials in various energy-storage materials.

In-situ self-assembled hollow urchins F-Co-MOF on rGO as advanced anodes for lithium-ion and sodium-ion batteries

To obtain MOFs materials with good electrochemical performance in both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), a kind of hollow urchins Co-MOF with doping fluorine (F) was in-situ assembled on reduced graphene oxide (rGO) using a simple solvothermal reaction. According to XRD, XPS and EDS mapping analysis, the molecular structure should be Co₂[F_x(OH)_1-x]₂(C₈O₄H₄) (denoted as F-Co-MOF). When the composite material is used as active material to assemble LIBs, it not only presents the outstanding reversible capacity (1202.0 mA h g^-1 at 0.1 A g^-1), but also gives the excellent rate performance and cycle performance (771.5 mA h g^-1 at 2 A g^-1 after 550 repeated cycles). The remarkable lithium storage capacity of F-Co-MOF/rGO is also reflected in the full cell, where it can still maintain a high capacity of 165.2 mA h g^-1 after 300 cycles at 0.2 A g^-1. It benefits from the synergistic effect of F-Co-MOF and high conductive rGO networks, so that the reversibility of lithium and sodium storage can be improved. This kind of F doped solvothermal synthesis of MOFs is of great significance for the exploration of high performance materials.

Rare earth material CeO2 modified CoS2 nanospheres for efficient photocatalytic hydrogen evolution

The construction of a heterojunction promoted the separation of electrons and holes, so that CeO2/CoS2 exhibited an excellent hydrogen evolution performance.

Fabrication of van der Waals Heterostructured FePSe3/Carbon Hybrid Nanosheets for Sodium Storage with High Performance

Iron phosphorus triselenide (FePSe₃) is attractive for energy applications owing to its interesting layered geometry, electronic structure, and physiochemical property, while it is limited in actual application because of a very long fabrication time of over 7 days. Herein, we report a new synthetic route to a high-quality sheetlike hybrid of iron phosphorus triselenide nanocrystals coated with graphitic carbon (FePSe₃/C) as an alternative kind of van der Waals heterostructures for the first time via a pyrolytic process at 600 °C from the precursors of ferrocene, red phosphorus, and selenium in a quartz tube with a significantly shortened reaction time of 24 h and even down to 30 min. Investigations demonstrated that the component phase of FePSe₃ in the layered FePSe₃/C hybrid nanosheets is the rhombohedral phase, and the hybrid nanosheets other than bulk crystals are about 15 nm in thickness. Acting as a cathode in fabricating half-cell sodium-ion batteries, the layered FePSe₃/C hybrid nanosheets exhibited remarkable performance. Typically, when current density was set as 50 mA g^-1, the hybrid nanosheet-assembled battery exhibited a capacity of 182.7 mA h g^-1 after performing over 50 cycles, and the nanosheet battery exhibited a capacity of 142 mA h g^-1 after performing for 200 cycling trials at 1 A g^-1 in the 0.8-2.2 V voltage window. Meanwhile, the layered FePSe₃/C hybrid nanosheets also exhibited very high rate capabilities at a relatively large current density in the present study, that is, 172 and 95 mA h g^-1 under typical performing conditions at 0.5 and 5 A g^-1, respectively.

Recent Advances on Mixed Metal Sulfides for Advanced Sodium-Ion Batteries

Sodium-ion batteries (SIBs) have drawn enormous attention in the past few years from both academic and industrial battery communities in view of the fascinating advantages of rich abundance and low cost of sodium resources. Among various electrode materials, mixed metal sulfides (MMSs) stand out as promising negative electrode materials for SIBs considering their superior structural and compositional advantages, such as decent electrochemical reversibility, high electronic conductivity, and rich redox reactions. Here, a summary of some recent developments in the rational design and synthesis of various kinds of MMSs with tailorable architectures, structural/compositional complexity, controllable morphologies, and enhanced electrochemical properties is presented. The effect of structural engineering and compositional design of MMSs on the sodium storage properties is highlighted. It is anticipated that further innovative works on the material design of advanced electrodes for batteries can be inspired.

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

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

Ion Reservoir Enabled by Hierarchical Bimetallic Sulfides Nanocages Toward Highly Effective Sodium Storage

Designing and constructing bimetallic hierarchical structures is vital for the conversion-alloy reaction anode of sodium-ion batteries (SIBs). Particularly, the rationally designed hetero-interface engineering can offer fast diffusion kinetics in the interface, leading to the improved high-power surface pseudocapacitance and cycling stability for SIBs. Herein, the hierarchical zinc-tin sulfide nanocages (ZnS-NC/SnS₂ ) are constructed through hydrothermal and sulfuration reactions. The unconventional hierarchical design with internal void space greatly optimizes the structure stability, and bimetallic sulfide brings a bimetallic composite interface and N heteroatom doping, which are devoted to high electrochemical activity and improved interfacial charge transfer rate for Na⁺ storage. Remarkably, the ZnS-NC/SnS₂ composite anode exhibits a delightful reversible capacity of 595 mAh g^-1 after 100 cycles at 0.2 A g^-1 , and long cycling capability for 500 cycles with a low capacity loss of 0.08% per cycle at 1 A g^-1 . This study opens up a new route for rationally constructing hierarchical heterogeneous interfaces and sheds new light on efficient anode material for SIBs.

Pore structure regulation of hard carbon: Towards fast and high-capacity sodium-ion storage

Hard carbon is regarded as one of the most promising anode material for sodium-ion batteries in virtue of the low cost and stable framework. However, the correlation between pore structures of hard carbon and sodium-ion storage is still ambiguous. In this work, based on precise control of pore-size distribution, the capacity, ion diffusion, and initial Coulombic efficiency were improved. Meanwhile, the relationship between pore structure and capacity was investigated. Our result indicates that the micropores hinder ion diffusion and hardly ever accommodate Na⁺ ions, while mesopores facilitate Na⁺ ion intercalation. Hard carbon with negligible micropores and abundant mesopores delivers a maximum capacity of 283.7 mAh g^-1 at 20 mA g^-1, which is 83% higher than that of micropore-rich one. Even after 320 cycles at 200 mA g^-1, the capacity still remains 189.4 mAh g^-1.

Highly pseudocapacitive metal-organic framework derived carbon skeleton supported Fe-Ti-O nanotablets as an anode material for efficient lithium storage

A facile and effective method to fabricate highly pseudocapacitive electrodes of Fe-Ti-O@C has been proposed here. In this strategy, FeOOH crystals were firstly grown uniformly on the surface of Ti-based MOF (MIL-125) tablet substrates through a solution immersion method, and then converted to uniform carbon supported Fe-Ti-O composites by calcination under argon. The obtained Fe-Ti-O@C composites were first utilized as an efficient anode for lithium ion batteries with a high reversible capacity of 988 mA h g^-1 after 160 cycles at 200 mA g^-1. Such a superior lithium storage performance may be due to the synergistic effect of the Fe₃O₄ nanoparticles with a high capacity, FeTiO₃ nanocomposites with a nearly stable structure during the Li⁺ insertion/removal process, and the conductive carbon skeleton with a large surface area and porous structure. This work represents an important step forward in the fabrication of MOF-derived hybrids and enables transition metal oxides (TMOs) to have potential applications in energy storage systems.

Rationally Designed Three-Layered Cu2 S@Carbon@MoS2 Hierarchical Nanoboxes for Efficient Sodium Storage

Hybrid materials, integrating the merits of individual components, are ideal structures for efficient sodium storage. However, the construction of hybrid structures with decent physical/electrochemical properties is still challenging. Now, the elaborate design and synthesis of hierarchical nanoboxes composed of three-layered Cu₂ S@carbon@MoS₂ as anode materials for sodium-ion batteries is reported. Through a facile multistep template-engaged strategy, ultrathin MoS₂ nanosheets are grown on nitrogen-doped carbon-coated Cu₂ S nanoboxes to realize the Cu₂ S@carbon@MoS₂ configuration. The design shortens the diffusion path of electrons/Na⁺ ions, accommodates the volume change of electrodes during cycling, enhances the electric conductivity of the hybrids, and offers abundant active sites for sodium uptake. By virtue of these advantages, these three-layered Cu₂ S@carbon@MoS₂ hierarchical nanoboxes show excellent electrochemical properties in terms of decent rate capability and stable cycle life.

Nanostructured metal chalcogenides confined in hollow structures for promoting energy storage

The engineering of progressive nanostructures with subtle construction and abundant active sites is a key factor for the advance of highly efficient energy storage devices. Nanostructured metal chalcogenides confined in hollow structures possess abundant electroactive sites, more ions and electron pathways, and high local conductivity, as well as large interior free space in a quasi-closed structure, thus showing promising prospects for boosting energy-related applications. This review focuses on the most recent progress in the creation of diverse confined hollow metal chalcogenides (CHMCs), and their electrochemical applications. Particularly, by highlighting certain typical examples from these studies, a deep understanding of the formation mechanism of confined hollow structures and the decisive role of microstructure engineering in related performances are discussed and analyzed, aiming at prompting the nanoscale engineering and conceptual design of some advanced confined metal chalcogenide nanostructures. This will appeal to not only the chemistry-, energy-, and materials-related fields, but also environmental protection and nanotechnology, thus opening up new opportunities for applications of CHMCs in various fields, such as catalysis, adsorption and separation, and energy conversion and storage.

A novel electrochemical immunosensor based on CoS2 for early screening of tumor marker carcinoembryonic antigen

In this work, PANI–HRP nanoparticles integrate biometric recognition and signal amplification functions in one body, which can be converted to each other without consuming the material itself.

Recent progress on metal–organic framework-derived materials for sodium-ion battery anodes

Recent progress on MOF-derived materials, including carbon and metal oxides/sulfides/selenides/phosphides, as anode materials for sodium-ion batteries is summarized.

Fabrication of an anode composed of a N, S co-doped carbon nanotube hollow architecture with CoS2 confined within: toward Li and Na storage

Over the years, transition metal chalcogenides (TMCs) have attracted ample attention from researchers on account of their high theoretical capacity, through which they show great potential for use in lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Nevertheless, there are some serious obstacles (particle pulverization and large volume change) still in the way to achieving satisfactory cycling performance and rate property. Here, we report the preparation of a N, S co-doped carbon nanotube hollow architecture confining CoS₂ (CoS₂/NSCNHF) derived from bimetal-organic-frameworks. The rationally designed structure possesses excellent Li⁺/Na⁺ storage performances. Further investigation of the Li⁺/Na⁺ storage behavior indicated the presence of a partial pseudocapacitive contribution, facilitating the fast Li⁺/Na⁺ interaction/extraction process and thus giving it superb electrochemical property. This work may represent an important step forward in the fabrication of MOF-derived hierarchical hybrids combined with a hollow structure and TMCs to help such TMCs achieve their potential in energy storage systems.

Sandwich-type electrochemical immunosensor constructed using three-dimensional lamellar stacked CoS2@C hollow nanotubes prepared by template-free method to detect carcinoembryonic antigen

Effective treatment of cancer depends on early detection of tumor markers. In this paper, an effective template-free method was used to prepare CoS₂@C three-dimensional hollow sheet nanotubes as the matrix of the immunosensor. The unique three-dimensional hybrid hollow tubular nanostructure provides greater contact area and enhanced detection limit. The CoS₂@C-NH₂-HRP nanomaterial was synthesized as a marker and had a high specific surface area, which can effectively improve the electrocatalytic ability of hydrogen peroxide (H₂O₂) reduction while increasing the amount of capture-fixed carcinoembryonic antigen antibody (anti-CEA). In addition, the co-bonded horseradish peroxidase (HRP) can further promote the redox of H₂O₂ and amplify the electrical signal. Carcinoembryonic antigen (CEA) was quantified by immediate current response (i-t), and the prepared immunosensor had good analytical performance under optimized conditions. The current signal and the concentration of CEA were linear in the range of 0.001-80 ng/mL, and the detection limit was 0.33 pg/mL (S/N = 3). The designed immunosensor has good selectivity, repeatability and stability, and the detection of human serum samples shows good performance. Furthermore, electrochemical immunosensor has broad application prospects in the clinical diagnosis of CEA.

Ionic-liquid-bifunctional wrapping of ultrafine SnO2 nanocrystals into N-doped graphene networks: high pseudocapacitive sodium storage and high-performance sodium-ion full cells

Sodium ion batteries are in great need of electrode materials with high specificity and rate capability being developed. The sluggish reaction kinetics of SnO2-based materials has impeded their applications as anodes of SIBs. Designing electrode materials with high pseudocapacitive contribution can increase the near-surface faradaic reaction, which helps to improve their kinetics and achieve high rate capability. Here, we designed a high-pseudocapacitance sodium storage anode SnO2/N-rGO by downsizing the particle size of SnO2 and constructing an N-doped graphene wrapped structure. The ultrafine structure of SnO2 ensures the high faradaic near-surface reaction, while the N-doped graphene matrix guarantees the superior electron and Na+ diffusion. Meanwhile, the wrapped N-doped graphene acts as a buffer layer to alleviate the volumetric changes of the active SnO2. The obtained ultrafine SnO2/N-graphene composite exhibits a high capacity of 607.6 mA h g-1 at 50 mA g-1 with an impressive rate capability (261.8 mA h g-1 at 2 A g-1) in Na+ half-cells. Furthermore, a good performance with a capacity of 133.3 mA h g-1 at 2.4 A g-1 in Na+ full-cells can also be achieved, which makes it a promising anode material for SIBs.

Nonaqueous Sodium-Ion Full Cells: Status, Strategies, and Prospects

With ever-increasing efforts focused on basic research of sodium-ion batteries (SIBs) and growing energy demand, sodium-ion full cells (SIFCs), as unique bridging technology between sodium-ion half-cells (SIHCs) and commercial batteries, have attracted more and more interest and attention. To promote the development of SIFCs in a better way, it is essential to gain a systematic and profound insight into their key issues and research status. This Review mainly focuses on the interface issues, major challenges, and recent progresses in SIFCs based on diversified electrolytes (i.e., nonaqueous liquid electrolytes, quasi-solid-state electrolytes, and all-solid-state electrolytes) and summarizes the modification strategies to improve their electrochemical performance, including interface modification, cathode/anode matching, capacity ratio, electrolyte optimization, and sodium compensation. Outlooks and perspectives on the future research directions to build better SIFCs are also provided.

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.

Metal-organic framework derived 3D graphene decorated NaTi2(PO4)3 for fast Na-ion storage

NASCION-type materials featuring super ionic conductivity are of considerable interest for energy storage in sodium ion batteries. However, the issue of inherent poor electronic conductivity of these materials represents a fundamental limitation in their utilization as battery electrodes. Here, for the first time, we develop a facile strategy for the synthesis of NASICON-type NaTi2(PO4)3/reduced graphene oxide (NTP-rGO) Na-ion anode materials from three-dimensional (3D) metal-organic frameworks (MOFs). The selected MOF serves as an in situ etching template for the titanium resource, and importantly, endows the materials with structure-directing properties for the self-assembly of graphene oxide (GO) through a one-step solvothermal process. Through the subsequent carbonization, an rGO decorated NTP architecture is obtained, which offers fast electron transfer and improved Na+ ion accessibility to active sites. Benefiting from its unique structural merits, the NTP-rGO exhibits improved sodium storage properties in terms of high capacity, excellent rate performance and good cycling life. We believe that the findings of this work provide new opportunities to design high performance NASICON-type materials for energy storage.

Sn nanocrystals embedded in porous TiO2/C with improved capacity for sodium-ion batteries

A cylinder-like Sn/TiO₂/C composite was prepared by carbonization and exhibited improved specific capacity in SIBs due to the combination of a porous TiO₂/C structure and Sn nanocrystals.