Neuron-Inspired Design of High-Performance Electrode Materials for Sodium-Ion Batteries

Constructing Hollow Microcubes SnS2 as Negative Electrode for Sodium-ion and Potassium-ion Batteries

Sodium/potassium-ion batteries (NIBs and KIBs) are considered the most promising candidates for lithium-ion batteries in energy storage fields. Tin sulfide (SnS2) is regarded as an attractive negative candidate for NIBs and KIBs thanks to its superior power density, high-rate performance and natural richness. Nevertheless, the slow dynamics, the enormous volume change and the decomposition of polysulfide intermediates limit its practical application. Herein, microcubes SnS2 were prepared through sacrificial MnCO3 template-assisted and a facile solvothermal reaction strategy and their performance was investigated in Na and K-based cells. The unique hollow cubic structure and well-confined SnS2 nanosheets play an important role in Na+/K+ rapid kinetic and alleviating volume change. The effect of the carbon additives (Super P/C65) on the electrochemical properties were investigated thoroughly. The in operando and ex-situ characterization provide a piece of direct evidence to clarify the storage mechanism of such conversion-alloying type negative electrode materials.

Anion Defects Engineering of Ternary Nb-Based Chalcogenide Anodes Toward High-Performance Sodium-Based Dual-Ion Batteries

Highlights

We developed an efficient and extensible strategy to produce the single-phase ternary NbSSe nanohybrids with defect-enrich microstructure. The anionic-Se doping play a key role in effectively modulating the electronic structure and surface chemistry of NbS2 phase, including the increased interlayers distance (0.65 nm), the enhanced intrinsic electrical conductivity (3.23 × 103 S m-1) and extra electroactive defect sites. The NbSSe/NC composite as anode exhibits rapid Na+ diffusion kinetics and increased capacitance behavior for Na+ storage, resulting in high reversible capacity and excellent cycling stability.

Abstract

Sodium-based dual-ion batteries (SDIBs) have gained tremendous attention due to their virtues of high operating voltage and low cost, yet it remains a tough challenge for the development of ideal anode material of SDIBs featuring with high kinetics and long durability. Herein, we report the design and fabrication of N-doped carbon film-modified niobium sulfur–selenium (NbSSe/NC) nanosheets architecture, which holds favorable merits for Na+ storage of enlarged interlayer space, improved electrical conductivity, as well as enhanced reaction reversibility, endowing it with high capacity, high-rate capability and high cycling stability. The combined electrochemical studies with density functional theory calculation reveal that the enriched defects in such nanosheets architecture can benefit for facilitating charge transfer and Na+ adsorption to speed the electrochemical kinetics. The NbSSe/NC composites are studied as the anode of a full SDIBs by pairing the expanded graphite as cathode, which shows an impressively cyclic durability with negligible capacity attenuation over 1000 cycles at 0.5 A g−1, as well as an outstanding energy density of 230.6 Wh kg−1 based on the total mass of anode and cathode.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40820-023-01070-0.

SiOxCy Microspheres with Homogeneous Atom Distribution for a High-Performance Li-Ion Battery

The broad application of silicon-based materials is limited by large volume fluctuation, high preparation costs, and complicated preparation processes. Here, we synthesized SiO_xC_y microspheres on 3D copper foams by a simple chemical vapor deposition method using a low-cost silane coupling agent (KH560) as precursors. The SiO_xC_y microspheres are available with a large mass loading (>3 mg/cm²) on collectors and can be directly used as the electrode without any binders or extra conductive agents. As a result, the as-prepared SiO_xC_y shows a high reversible capacity of ∼1240 mAh g^-1 and can be cycled more than 1900 times without decay. Ex situ characterizations show that the volume change of the microspheres is only 55% and the spherical morphology as well as the 3D structure remain intact after cycles. Full-cell electrochemical tests paired with LiFePO₄ as cathodes show 87% capacity retention after 500 cycles, better than most reported results, thus showing the commercial potential of the material.

Structure Engineering of BiSbSx Nanocrystals Embedded within Sulfurized Polyacrylonitrile Fibers for High Performance of Potassium-Ion Batteries

Potassium-ion batteries (PIBs) are regarded as promising candidates in next-generation energy storage technology; however, the electrode materials in PIBs are usually restricted by the shortcomings of large volume expansion and poor cycling stability stemming from a high resistance towards diffusion and insertion of large-sized K ions. In this study, BiSbS_x nanocrystals are rationally integrated with sulfurized polyacrylonitrile (SPAN) fibres through electrospinning technology with an annealing process. Such a unique structure, in which BiSbS_x nanocrystals are embedded inside the SPAN fibre, affords multiple binding sites and a short diffusion length for K⁺ to realize fast kinetics. In addition, the molecular structure of SPAN features robust chemical interactions for stationary diffluent discharge products. Thus, the electrode demonstrates a superior potassium storage performance with an excellent reversible capacity of 790 mAh g^-1 (at 0.1 A g^-1 after 50 cycles) and 472 mAh g^-1 (at 1 A g^-1 after 2000 cycles). It's one of the best performances for metal dichalcogenides anodes for PIBs to date. The unusual performance of the BiSbS_x @SPAN composite is attributed to the synergistic effects of the judicious nanostructure engineering of BiSbS_x nanocrystals as well as the chemical interaction and confinement of SPAN fibers.

In Situ Growth of W2C/WS2 with Carbon-Nanotube Networks for Lithium-Ion Storage

The combination of W₂C and WS₂ has emerged as a promising anode material for lithium-ion batteries. W₂C possesses high conductivity but the W₂C/WS₂-alloy nanoflowers show unstable performance because of the lack of contact with the leaves of the nanoflower. In this study, carbon nanotubes (CNTs) were employed as conductive networks for in situ growth of W₂C/WS₂ alloys. The analysis of X-ray diffraction patterns and scanning/transmission electron microscopy showed that the presence of CNTs affected the growth of the alloys, encouraging the formation of a stacking layer with a lattice spacing of ~7.2 Å. Therefore, this self-adjustment in the structure facilitated the insertion/desertion of lithium ions into the active materials. The bare W₂C/WS₂-alloy anode showed inferior performance, with a capacity retention of ~300 mAh g⁻¹ after 100 cycles. In contrast, the WCNT01 anode delivered a highly stable capacity of ~650 mAh g⁻¹ after 100 cycles. The calculation based on impedance spectra suggested that the presence of CNTs improved the lithium-ion diffusion coefficient to 50 times that of bare nanoflowers. These results suggest the effectiveness of small quantities of CNTs on the in situ growth of sulfides/carbide alloys: CNTs create networks for the insertion/desertion of lithium ions and improve the cyclic performance of metal-sulfide-based lithium-ion batteries.

Facile fabrication of WS2 nanocrystals confined in chlorella-derived N, P co-doped bio-carbon for sodium-ion batteries with ultra-long lifespan

Sodium-ion batteries (SIBs) have been regarded as a promising substitute for lithium-ion batteries but there are still formidable challenges in developing an anode material with adequate lifespan and outstanding rate performance. Transition metal dichalcogenides (TMDs) are promising anode materials for SIBs due to their high theoretical capacities. However, their severe volume expansions and low electronic conductivity impede their practical developments. In addition, the synthesis of energy storage materials from waste biomass has aroused extensive attention. Herein, we synthesize WS₂ nanocrystals embedded in N and P co-doped biochar via a facile bio-sorption followed by sulphurization, employing waste chlorella as the adsorbent and bio-reactor. The WS₂ nanocrystals are beneficial for storing more sodium ions and expediting the transportation of sodium ions, thus improving the capacity and reaction kinetics. Chlorella acts as a reactor and not only inhibits the stacking of WS₂ nanocrystals during the synthesis process but also alleviates the mechanical pressure of composite during the charge/discharge process. As a result, the WS₂/NPC-2 electrode delivers a high specific capacity (436 mA h g^-1 at 0.1 A g^-1) and superior rate performance of 311 mA h g^-1 at 3 A g^-1 for SIBs. It also exhibits excellent stability even up to 6000 cycles at 5 A g^-1, which is one of the optimal long-cycle properties reported for WS₂-based materials to date.

Three-dimensional microspheres constructed with MoS2 nanosheets supported on multiwalled carbon nanotubes for optimized sodium storage

Molybdenum disulfide (MoS2) has been regarded as a promising anode material in the field of sodium-ion batteries (SIBs), with the advantages of high theoretical capacity and large interlayer spacings. Unfortunately, its intrinsic poor electrical conductivity and large volume changes during the sodiation/desodiation reactions still limit its practical application. To deal with this shortcoming, we built MoS2 nanosheet/multiwalled carbon nanotube (denoted as MoS2-MSs/MWCNTs) composites with a three-dimensional (3D) micro-spherical structure, assembled in situ from MoS2 nanosheets. These nanosheets are connected to each other by the MWCNTs network, which provides a highly conductive pathway for electrons/ions through interparticle and intraparticle interfaces, accelerating charge transfer and ion diffusion capabilities. More importantly, the carbon network can boost electrical conductivity and relieve structural strain. Consequently, the as-prepared MoS2-MSs/MWCNTs composite presents a high reversible specific capacity of 519 mA h g-1 at 0.1 A g-1 after 100 cycles with a capacity retention of 94.4% and excellent rate performance (227 mA h g-1 at 10 A g-1). Outstanding cycling stability was also achieved (327.1 mA h g-1 over 1000 cycles at 2 A g-1) and was characterized by scanning electron microscopy (SEM) analysis. Our findings provide a simple and effective strategy to explore anode materials with advanced sodium storage properties.

Nature-inspired hierarchical materials for sensing and energy storage applications

Nature-inspired hierarchical architectures have recently drawn enormous interest in the materials science community, being considered as promising materials for the development of high-performance wearable electronic devices. Their highly dynamic interfacial interactions have opened new horizons towards the fabrication of sustainable sensing and energy storage materials with multifunctional properties. Nature-inspired assemblies can exhibit impressive properties including ultrahigh sensitivity, excellent energy density and coulombic efficiency behaviors as well as ultralong cycling stability and durability, which can be finely tuned and enhanced by controlling synergistic interfacial interactions between their individual components. This tutorial review article aims to address recent breakthroughs in the development of advanced Nature-inspired sensing and energy storage materials, with special emphasis on the influence of interfacial interactions over their improved properties.

Template-free fabrication of 1D core-shell MoO2@MoS2/nitrogen-doped carbon nanorods for enhanced lithium/sodium-ion storage

A universal anode material of 1D core-shell MoO₂@MoS₂/nitrogen-doped carbon (MoO₂@MoS₂/NC) nanorods has been elaborately synthesized via a facile fabrication route for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), in which MoO₂ core not only acts as a conductive backbone for efficient electron transport, but creates structural disorders in MoS₂ nanosheets to prevent aggregation and expose more active sites for alkali-ions. Meanwhile, the MoO₂ core is tightly encapsulated by the parallelly aligned MoS₂ nanosheets to constrain the size of crystals, which greatly shortens the ionic diffusion path and accelerates diffusion rate, thus ensuring fast reaction kinetics. Additionally, the resilient and conductive N-doped carbon matrix in the hybrid could maintain the structural integrity and enhance the electrical conductivity of the electrodes, improving the rate capability and life span. The flexible 1D nanorods could contract freely during the charge/discharge process, further assuring the structural stability of the electrodes. Benefiting from the above-mentioned advantages, the MoO₂@MoS₂/NC electrodes still remains a specific capacity of 583.5 mA h g^-1 after 1500 cycles at a high current density up to 10 A g^-1 in LIBs, and a capacity of 419.8 mA h g^-1 is steadily kept over 800 cycles at 2 A g^-1 in SIBs.

Co-construction of sulfur vacancies and carbon confinement in V5S8/CNFs to induce an ultra-stable performance for half/full sodium-ion and potassium-ion batteries

The construction of anode materials for sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) with a high energy and a long lifespan is significant and still challenging. Here, sulfur-defective vanadium sulfide/carbon fiber composites (D-V5S8/CNFs) are designed and fabricated by a facile electrospinning method, followed by sulfuration treatment. The unique architecture, in which V5S8 nanoparticles are confined inside the carbon fiber, provides a short-range channel and abundant adsorption sites for ion storage. Moreover, enlarged interlayer spacings could also alleviate the volume changes, and offer small vdW interactions and ionic diffusion resistance to store more Na and K ions reversibly and simultaneously. The DFT calculations further demonstrate that sulfur defects can effectively facilitate the adsorption behavior of Na+ and K+ and offer low energy barriers for ion intercalation. Taking advantage of the functional integration of these merits, the D-V5S8/CNF anode exhibits excellent storage performance and long-term cycling stability. It reveals a high capacity of 462 mA h g-1 at a current density of 0.2 A g-1 in SIBs, while it is 350 mA h g-1 at 0.1 A g-1 in PIBs, as well as admirable long-term cycling characteristics (190 mA h g-1/17 000 cycles/5 A g-1 for SIBs and 165 mA h g-1/3000 cycles/1 A g-1 for PIBs). Practically, full SIBs upon pairing with a Na3V2(PO4)3 cathode also exhibit superior performance.

In situ hydrothermal synthesis of double-carbon enhanced novel cobalt germanium hydroxide composites as promising anode material for sodium ion batteries

Germanium (Ge)-based materials are considered to be one of the most promising anode materials for sodium-ion batteries (SIBs). Nevertheless, the practical electrochemical performance is severely hampered by poor cyclability due to volumetric expansion of Ge upon cycling. Herein, double-carbon confined cobalt germanium hydroxide (CGH@C/rGO) composites has been facilely synthesized with the supportion of l-ascorbic acid and graphene oxide (GO) as anode materials for sodium-ion storage. As a result, the CGH@C/rGO anode delivers a high cyclic stability with a reversible capacity of 416 mA h g^-1 after 100 cycles at 100 mA g^-1 and an excellent rate capability of 206 mA h g^-1 at 2000 mA g^-1 compared with CGH, CGH@C and CGH/rGO composites. Besides, the reversible capacity of 266 mA h g^-1 still remained even after 500 cycles at current density of 1 A g^-1. Such outstanding electrochemical performance could be accredited to a strong interaction between CGH, carbon, and graphene, which increases the electronic conductivity, relieves the volume expansion aroused by sodiation/desodiation, shortens the pathway of electron/ion transportation that further improving the reaction kinetics and endowing the material with remarkable cycling capability. Obviously, this in situ hydrothermal synthesis of double carbon coating strategy can be extended to designing other candidates of anode materials for SIBs.

Dual carbon decorated germanium-carbon composite as a stable anode for sodium/potassium-ion batteries

In the present work, we introduce a dual carbon accommodated structure in which germanium nanoparticles are encapsulated into an ordered mesoporous carbon matrix (Ge-CMK) and further coated with an amorphous carbon layer (Ge@C-CMK) through a nano-casting route followed by chemical vapor deposition (CVD) treatment. In the resultant Ge@C-CMK composite, the unique lane-like pore structure that cooperates with the amorphous carbon surface can not only mitigate the volume expansion of germanium particles, but also improve the electrical conductivity of germanium as well as facilitate Na⁺/K⁺ diffusion. When employed as the anode of sodium-ion batteries, the Ge@C-CMK electrode exhibits stable capacity as well as long-term cycling stability (a stable capacity of 176 mAh g^-1 at 1 A g^-1 after 5000 cycles). Furthermore, it also delivers a reversible capacity when used as the anode of potassium-ion batteries. This demonstrates that the Ge@C-CMK electrode possesses promising application potential as an alternative anode in sodium and potassium ion storage applications.

Construction of a C@MoS2@C sandwiched heterostructure for accelerating the pH-universal hydrogen evolution reaction

Herein a facile and versatile hydrothermal method has been developed to construct a polypyrrole-derived carbon nanotube (PCN), MoS2 nanosheets and a carbon shell integrated sandwich-like heterostructure (PCN@MoS2@C). This heterostructure shows excellent performance in the hydrogen evolution reaction (HER) over a wide pH range. The results indicate that the porous carbon shell coated heterostructure provides MoS2 nanosheets with sufficient conductivity, increased number of active sites, and strong structural stability, and thus boosts its HER performance.

State-of-the-Art Electrode Materials for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) were investigated as recently as in the seventies. However, they have been overshadowed for decades, due to the success of lithium-ion batteries that demonstrated higher energy densities and longer cycle lives. Since then, the witness a re-emergence of the SIBs and renewed interest evidenced by an exponential increase of the publications devoted to them (about 9000 publications in 2019, more than 6000 in the first six months this year). This huge effort in research has led and is leading to an important and constant progress in the performance of the SIBs, which have conquered an industrial market and are now commercialized. This progress concerns all the elements of the batteries. We have already recently reviewed the salts and electrolytes, including solid electrolytes to build all-solid-state SIBs. The present review is then devoted to the electrode materials. For anodes, they include carbons, metal chalcogenide-based materials, intercalation-based and conversion reaction compounds (transition metal oxides and sulfides), intermetallic compounds serving as functional alloying elements. For cathodes, layered oxide materials, polyionic compounds, sulfates, pyrophosphates and Prussian blue analogs are reviewed. The electrode structuring is also discussed, as it impacts, importantly, the electrochemical performance. Attention is focused on the progress made in the last five years to report the state-of-the-art in the performance of the SIBs and justify the efforts of research.

A MoS2@SnS heterostructure for sodium-ion storage with enhanced kinetics

Layered metal sulphides are promising anode materials for sodium-ion batteries (SIBs) and capacitors owing to their distinctive crystal structures and large interlayer spacings, which are suitable for Na⁺ insertion/extraction. However, low electronic conductivity, sluggish ion transfer and large volume variation of metal sulphides during sodiation/desodiation processes have hindered their practical application. In this work, we report the construction of a walnut-like core-shell MoS₂@SnS heterostructure composite as an anode for SIBs with high capacity, remarkable rate and superior cycling stability. Experimental observations and first-principles density functional theory (DFT) calculations reveal that the enhanced electrochemical performances can be mainly ascribed to the boosted charge transfer and ion diffusion capabilities at the heterostructure interface driven by a self-building internal electric field. Our findings herein may pave the way for the development of novel heterostructure composite materials for beyond lithium-ion batteries and capacitors.

Confinement Growth of Layered WS2 in Hollow Beaded Carbon Nanofibers with Synergistic Anchoring Effect to Reinforce Li+ /Na+ Storage Performance

Novel nitrogen doped (N-doped) hollow beaded structural composite carbon nanofibers are successfully applied for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Tungsten disulfide (WS₂ ) nanosheets are confined, through synergistic anchoring, on the surface and inside of hollow beaded carbon nanofibers (HB CNFs) via a hydrothermal reaction method to construct the hierarchical structure HB WS₂ @CNFs. Benefiting from this unique advantage, HB WS₂ @CNFs exhibits remarkable lithium-storage performance in terms of high rate capability (≈351 mAh g^-1 at 2 A g^-1 ) and stable long-term cycle (≈446 mAh g^-1 at 1 A g^-1 after 100 cycles). Moreover, as an anode material for SIBs, HB WS₂ @CNFs obtains excellent long cycle life and rate performance. During the charging/discharging process, the evolution of morphology and composition of the composite are analyzed by a set of ex situ methods. This synergistic anchoring effect between WS₂ nanosheets and HB CNFs is capable of effectively restraining volume expansion from the metal ions intercalation/deintercalation process and improving the cycling stability and rate performance in LIBs and SIBs.

Facile fabrication of a vanadium nitride/carbon fiber composite for half/full sodium-ion and potassium-ion batteries with long-term cycling performance

Vanadium-based composite anodes have been designed for applications in alkali metal ion batteries, including lithium-ion batteries (LIBs), sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs). However, the problems of inferior long-term cycling stability caused by the large volume change and dissolution of vanadium-based active materials during cycles and slow diffusion for large radii of Na⁺ and K⁺ still limit their underlying capability and need to be addressed. In the present work, we initially designed and fabricated a vanadium nitride/carbon fiber (VN/CNF) composite via a facile electrospinning method followed by the ammonization process. The obtained VN/CNF composite anode exhibited excellent half/full sodium and potassium storage performance. When used as an anode material for SIBs, it delivered a high capacity of 403 mA h g^-1 at 0.1 A g^-1 after 100 cycles and as large as 237 mA h g^-1 at 2 A g^-1 even after 4000 cycles with negligible capacity fading. More importantly, the VN/CNFs//Na₃V₂(PO₄)₃ full cell by coupling the VN/CNF composite anode with the Na₃V₂(PO₄)₃ (NVP) cathode also exhibited a desirable capacity of 257 mA h g^-1 at 500 mA g^-1 after 50 cycles. Besides, when further evaluated as an anode for PIBs, the VN/CNF composite anode achieved a large capacity of 266 mA h g^-1 after 200 cycles at 0.1 A g^-1 and maintained a stable capacity of 152 mA h g^-1 at 1 A g^-1 even after 1000 cycles, showing significant long-term cycling stability. This is one of the best performances of vanadium-based anode materials for SIBs and PIBs reported so far.

In Situ Recyclable Surface-Enhanced Raman Scattering-Based Detection of Multicomponent Pesticide Residues on Fruits and Vegetables by the Flower-like MoS2@Ag Hybrid Substrate

Pesticides, extensively used in agriculture production, have received enormous attention because of their potential threats to the environment and human health. Hence, in this study, a kind of highly sensitive and stable hybrid surface-enhanced Raman scattering (SERS)-active substrates constructed with flower-like two-dimensional molybdenum sulfide and Ag (MoS₂@Ag) has been developed, and then the above substrate was sequentially utilized in the recyclable detection of pesticide residues on several kinds of fruits and vegetables. In the first place, the excellent photocatalytic performance of the MoS₂@Ag hybrid substrate was demonstrated, which was attributed to the inhibition of electron-hole combination after the formation of Schottky barrier between the Ag NPs and MoS₂ matrix. Thereafter, two calibration curves with ultra-low limits of detection (LOD) as 6.4 × 10^-7 and 9.8 × 10^-7 mg/mL were established for the standard solutions of thiram (tetramethylthiuram disulfide, TMTD) and methyl parathion (MP), and then the recyclable assay of their single and mixed residues on eggplant, Chinese cabbage, grape, and strawberry was successfully realized. It is interesting to note that the detection recoveries from 95.5 to 63.1% for TMTD and 92.3 to 62.6% for MP are greatly dependent on the size and surface roughness of these foods. In a word, the MoS₂@Ag composite matrix shows attractive SERS and photocatalysis performance, and it is expected to have the potential application on food safety monitoring.

Confined growth of 2D MoS2 nanosheets in N-doped pearl necklace-like structured carbon nanofibers with boosted lithium and sodium storage performance

N-Doped amber necklace-like structured MoS₂@carbon nanofibers (ANL MoS₂@CNFs) were fabricated via the confined growth, constructing a hierarchical structure with 2D nanosheets, yolk–shell structures, 1D nanofibers, and 3D cross-linked networks.

A composite of ultra-fine few-layer MoS2 structures embedded on N,P-co-doped bio-carbon for high-performance sodium-ion batteries

Highly dispersed ultra-fine few-layer MoS₂ embedded on N/P co-doped bio-carbon composite (MoS₂-N/P-C) was synthesized and it delivers excellent high-rate long term cycling performance (175 mA h g⁻¹ after 2000 cycles at 5 A g⁻¹).

Tailoring Coral-Like Fe7Se8@C for Superior Low-Temperature Li/Na-Ion Half/Full Batteries: Synthesis, Structure, and DFT Studies

The intrinsic charge-transfer property bears the primary responsibility for the sluggish redox kinetics of the common electrode materials, especially operated at low temperatures. Herein, we report the crafting of homogeneously confined Fe₇Se₈ nanoparticles with a well-defined graphitic carbon matrix that demonstrate a highly efficient charge-transfer system in a designed natural coral-like structure (cl-Fe₇Se₈@C). Notably, the intricate architecture as well as highly conductive peculiarity of C concurrently satisfy the demands of achieving fast ionic/electrical conductivities for both Li/Na-ion batteries in a wide temperature range. For example, when cl-Fe₇Se₈@C is employed as the anode material to assemble full batteries with the cathode of Na₃V₂(PO₄)₂O₂F (NVPOF), decent capacities of 323.1 and 175.9 mA h g^-1 can be acquired at temperatures of 25 and -25 °C, respectively. This work is significant for further developing potential anode materials for advanced energy storage and conversion under low-temperature conditions.

Core-shell anatase anode materials for sodium-ion batteries: the impact of oxygen vacancies and nitrogen-doped carbon coating

In this work, the impact of oxygen vacancies and nitrogen-doped carbon coating on the sodium-ion storage properties of anatase TiO2 has been demonstrated. Oxygen vacancies and nitrogen-doped carbon coating were introduced simultaneously by the calcination of core-shell structured TiO2 spheres in a reducing atmosphere. Compared to the anatase TiO2 with and without oxygen vacancies, TiO2-x@NC exhibits much better electrochemical performance in the storage of sodium ions. A high reversible capacity of 245.6 mA h g-1 is maintained at 0.1 A g-1 after 200 cycles, and a high specific capacity of 155.6 mA h g-1 is achieved at a high rate of 5.0 A g-1. The significantly improved electrochemical performance of the core-shell structured anatase TiO2 spheres is attributed to the synergistic effect of the oxygen vacancies in the anatase lattice and surface nitrogen-doped carbon coating. This work provides an efficient strategy for improving the electrochemical performance of metal-oxide-based electrode materials for sodium-ion batteries.

Electrospun VSe1.5/CNF composite with excellent performance for alkali metal ion batteries

Exploring advanced anode materials with excellent electrochemical performance for rechargeable batteries, including lithium-ion batteries (LIBs), sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs), has attracted great attention. However, low electronic conductivity, severe particle agglomeration and lack of effective synthesis methods have still greatly hampered their rapid development. Herein, we initially fabricate a novel VSe_1.5/CNF composite through a facile electrospinning method followed by selenization. The electrochemical measurements show that VSe_1.5/CNFs can enable the rapid and durable storage of Li⁺, Na⁺, and K⁺ ions. When used as an anode material for LIBs, the VSe_1.5/CNF composite delivers a high capacity of 932 mA h g^-1 after 400 cycles at a high current density of 1 A g^-1. In addition, for SIBs, the VSe_1.5/CNF composite manifests a high reversible capacity of 668 mA h g^-1 after 50 cycles and an excellent capacity of 265 mA h g^-1 at 2 A g^-1 even after an ultra-long 6000 cycles. This is one of the best performances of vanadium-based anode materials for SIBs reported so far. Most remarkably, the VSe_1.5/CNF composite also demonstrates a satisfactory reversible K⁺ storage performance. The simple synthetic route and excellent ion storage properties make the VSe_1.5/CNF composite a great prospect for application as an anode material for alkali metal ion batteries.

Conductive carbon nanofiber interpenetrated graphene architecture for ultra-stable sodium ion battery

Long-term stability and high-rate capability have been the major challenges of sodium-ion batteries. Layered electroactive materials with mechanically robust, chemically stable, electrically and ironically conductive networks can effectively address these issues. Herein we have successfully directed carbon nanofibers to vertically penetrate through graphene sheets, constructing robust carbon nanofiber interpenetrated graphene architecture. Molybdenum disulfide nanoflakes are then grown in situ alongside the entire framework, yielding molybdenum disulfide@carbon nanofiber interpenetrated graphene structure. In such a design, carbon nanofibers prevent the restacking of graphene sheets and provide ample space between graphene sheets, enabling a strong structure that maintains exceptional mechanical integrity and excellent electrical conductivity. The as-prepared sodium ion battery delivers outstanding electrochemical performance and ultrahigh stability, achieving a remarkable specific capacity of 598 mAh g⁻¹, long-term cycling stability up to 1000 cycles, and an excellent rate performance even at a high current density up to 10 A g⁻¹.

Here the authors construct carbon nanofiber interpenetrated graphene architecture with in-situ grown MoS₂ nanoflakes alongside the framework. The design combines exceptional mechanical integrity and excellent electronic conductivity, enabling outstanding electrochemical performance in sodium-ion battery.

Growth of Bouquet-like Zn2GeO4 Crystal Clusters in Molten Salt and Understanding the Fast Na-Storage Properties

The exploration of high-performance anode materials is imperative for the development of sodium-ion batteries (SIBs). Herein, a molten-salt-assisted approach is developed to prepare crystallized Zn₂GeO₄ clusters constructed by interconnected nanorods, and the Na-ion storage mechanism is studied systemically through in situ X-ray diffraction, ex situ X-ray photoelectron spectroscopy, and high-resolution transmission microscopy associated with galvanostatic intermittent titration technique. The Zn₂GeO₄ anode undergoes conversion reactions followed by the alloying reaction. The large channel in the Zn₂GeO₄ crystal structure ensures insertion of sodium ions. The amorphous transformation during the initial discharge process increases the active site for the fast electrochemical reaction. As the anode for SIBs, the Zn₂GeO₄ cluster exhibits good rate capability with a capacity retention of 111.1 mA h g^-1 at 20 A g^-1 in half cells and 118.9 mA h g^-1 at 2 A g^-1 in full cells, associated with a capacity of 184.2 mA h g^-1 at 0.5 A g^-1 after 500 cycles. The ex situ scanning electron microscopy images of the electrode material disclose that the hierarchical structure can accommodate the volume variation of Zn₂GeO₄ during discharge/charge cycling, facilitating long cycling stability. The investigation of Zn₂GeO₄ provides new insight for the development of high-rate anode materials for SIBs.

α-Fe2 O3 Nanoparticles Decorated C@MoS2 Nanosheet Arrays with Expanded Spacing of (002) Plane for Ultrafast and High Li/Na-Ion Storage

MoS₂ nanosheets as a promising 2D nanomaterial have extensive applications in energy storage and conversion, but their electrochemical performance is still unsatisfactory as an anode for efficient Li⁺ /Na⁺ storage. In this work, the design and synthesis of vertically grown MoS₂ nanosheet arrays, decorated with graphite carbon and Fe₂ O₃ nanoparticles, on flexible carbon fiber cloth (denoted as Fe₂ O₃ @C@MoS₂ /CFC) is reported. When evaluated as an anode for lithium-ion batteries, the Fe₂ O₃ @C@MoS₂ /CFC electrode manifests an outstanding electrochemical performance with a high discharge capacity of 1541.2 mAh g^-1 at 0.1 A g^-1 and a good capacity retention of 80.1% at 1.0 A g^-1 after 500 cycles. As for sodium-ion batteries, it retains a high reversible capacity of 889.4 mAh g^-1 at 0.5 A g^-1 over 200 cycles. The superior electrochemical performance mainly results from the unique 3D ordered Fe₂ O₃ @C@MoS₂ array-type nanostructures and the synergistic effect between the C@MoS₂ nanosheet arrays and Fe₂ O₃ nanoparticles. The Fe₂ O₃ nanoparticles act as spacers to steady the structure, and the graphite carbon could be incorporated into MoS₂ nanosheets to improve the conductivity of the whole electrode and strengthen the integration of MoS₂ nanosheets and CFC by the adhesive role, together ensuring high conductivity and mechanical stability.

Rational design of few-layer MoSe2 confined within ZnSe-C hollow porous spheres for high-performance lithium-ion and sodium-ion batteries

Rechargeable battery systems, including Li-ion batteries and Na-ion batteries, have attracted great interest in energy storage because of their high energy density, low cost, efficient energy storage and suitable redox potential. Nevertheless, their rapid development is still greatly hampered by some typical constraints including low coulombic efficiency, large volume changes and severe particle agglomeration and pulverization during the charge-discharge process. Here, we fabricate a few-layer MoSe2 confined within a ZnSe-C hollow porous sphere nanocomposite through a simple self-assembly strategy followed by selenization, which efficiently circumvents these problems. The fabricated ZnSe/MoSe2@C electrode demonstrates diverse advantages, including the existence of a few-layer structure, an in situ porous carbon matrix, multicomponent coordination and excellent pseudocapacitive behavior. When used as an anode material, it displays extraordinarily attractive electrochemical performance for both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). The reversible capacity of ZnSe/MoSe2@C for LIBs reaches as high as 1051 mA h g-1 at 0.2 A g-1 (150 cycles). A long-term high-rate cycling test reveals an excellent stability of 524 mA h g-1 at 4 A g-1 after 600 cycles. In addition, for SIBs, ZnSe/MoSe2@C also manifests a high initial coulombic efficiency of 89% at 0.2 A g-1 and a remarkable reversible capacity of 381 mA h g-1 at a high current density of 4 A g-1 even after 250 cycles with negligible capacity loss. This is one of the best performances of ZnSe-based anode materials for SIBs reported so far. The regulation strategy reported in the present work is expected to offer new insights into the fabrication of high performance anode materials for SIBs.

An ultra-small few-layer MoS2-hierarchical porous carbon fiber composite obtained via nanocasting synthesis for sodium-ion battery anodes with excellent long-term cycling performance

Rational fabrication of anode electrodes for sodium-ion batteries remains a challenge due to the problem of sluggish Na+ diffusion kinetics, large volume expansion etc. Significant efforts, such as fabricating carbon composites and novel nanostructures, have been devoted to the development of anode materials. Herein, an ultra-small few-layer MoS2 nanostructure confined on a hierarchical porous carbon fiber composite was synthesized through the nanocasting route using a novel hierarchical porous carbon fiber as the template. As an anode material, the composite displays outstanding electrochemical performance for sodium-ion batteries. For instance, it delivers high reversible capacities (491 mA h g-1 after 50 cycles at 0.1 A g-1), high rate performance (387 mA h g-1 at 2 A g-1) and long-term cycling stability (234 mA h g-1 at 1 A g-1 after 3000 cycles). Note that it shows one of the best long-term cycling properties reported to date for MoS2-based anode materials for sodium-ion batteries. This regulation strategy may offer new insights into the fabrication of high-performance anode materials for sodium-ion batteries.

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.

An Sn doped 1T–2H MoS2 few-layer structure embedded in N/P co-doped bio-carbon for high performance sodium-ion batteries

A facile route for fabrication of an Sn doped 1T–2H MoS₂ few-layer structure embedded in N/P co-doped bio-carbon is initially developed using natural chlorella as an adsorbent and a nanoreactor.