Designed Formation of Hybrid Nanobox Composed of Carbon Sheathed CoSe2 Anchored on Nitrogen‐Doped Carbon Skeleton as Ultrastable Anode for Sodium‐Ion Batteries

Research on sodium‐ion batteries (SIBs) has recently been revitalized due to the unique features of much lower costs and comparable energy/power density to lithium‐ion batteries (LIBs), which holds great potential for grid‐level energy storage systems. Transition metal dichalcogenides (TMDCs) are considered as promising anode candidates for SIBs with high theoretical capacity, while their intrinsic low electrical conductivity and large volume expansion upon Na⁺ intercalation raise the challenging issues of poor cycle stability and inferior rate performance. Herein, the designed formation of hybrid nanoboxes composed of carbon‐protected CoSe₂ nanoparticles anchored on nitrogen‐doped carbon hollow skeletons (denoted as CoSe₂@C∩NC) via a template‐assisted refluxing process followed by conventional selenization treatment is reported, which exhibits tremendously enhanced electrochemical performance when applied as the anode for SIBs. Specifically, it can deliver a high reversible specific capacity of 324 mAh g^?1 at current density of 0.1 A g^?1 after 200 cycles and exhibit outstanding high rate cycling stability at the rate of 5 A g^?1 over 2000 cycles. This work provides a rational strategy for the design of advanced hybrid nanostructures as anode candidates for SIBs, which could push forward the development of high energy and low cost energy storage devices.     

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.     

Porous Carbon Nanofibers Encapsulated with Peapod‐Like Hematite Nanoparticles for High‐Rate and Long‐Life Battery Anodes

Fe₂O₃ is regarded as a promising anode material for lithium‐ion batteries (LIBs) and sodium‐ion batteries (SIBs) due to its high specific capacity. The large volume change during discharge and charge processes, however, induces significant cracking of the Fe₂O₃ anodes, leading to rapid fading of the capacity. Herein, a novel peapod‐like nanostructured material, consisting of Fe₂O₃ nanoparticles homogeneously encapsulated in the hollow interior of N‐doped porous carbon nanofibers, as a high‐performance anode material is reported. The distinctive structure not only provides enough voids to accommodate the volume expansion of the pea‐like Fe₂O₃ nanoparticles but also offers a continuous conducting framework for electron transport and accessible nanoporous channels for fast diffusion and transport of Li/Na‐ions. As a consequence, this peapod‐like structure exhibits a stable discharge capacity of 1434 mAh g^?1 (at 100 mA g^?1) and 806 mAh g^?1 (at 200 mA g^?1) over 100 cycles as anode materials for LIBs and SIBs, respectively. More importantly, a stable capacity of 958 mAh g^?1 after 1000 cycles and 396 mAh g^?1 after 1500 cycles can be achieved for LIBs and SIBs, respectively, at a large current density of 2000 mA g^?1. This study provides a promising strategy for developing long‐cycle‐life LIBs and SIBs.     

Unique Cobalt Sulfide/Reduced Graphene Oxide Composite as an Anode for Sodium‐Ion Batteries with Superior Rate Capability and Long Cycling Stability

Exploitation of high‐performance anode materials is essential but challenging to the development of sodium‐ion batteries (SIBs). Among all proposed anode materials for SIBs, sulfides have been proved promising candidates due to their unique chemical and physical properties. In this work, a facile solvothermal method to in situ decorate cobalt sulfide (CoS) nanoplates on reduced graphene oxide (rGO) to build CoS@rGO composite is described. When evaluated as anode for SIBs, an impressive high specific capacity (540 mAh g^?1 at 1 A g^?1), excellent rate capability (636 mAh g^?1 at 0.1 A g^?1 and 306 mAh g^?1 at 10 A g^?1), and extraordinarily cycle stability (420 mAh g^?1 at 1 A g^?1 after 1000 cycles) have been demonstrated by CoS@rGO composite for sodium storage. The synergetic effect between the CoS nanoplates and rGO matrix contributes to the enhanced electrochemical performance of the hybrid composite. The results provide a facile approach to fabricate promising anode materials for high‐performance SIBs.     

SnS2/Co3S4 Hollow Nanocubes Anchored on S‐Doped Graphene for Ultrafast and Stable Na‐Ion Storage

SnS₂ has been widely studied as an anode material for sodium‐ion batteries (SIBs) based on the high theoretical capacity and layered structure. Unfortunately, rapid capacity decay associated with volume variation during cycling limits practical application. Herein, SnS₂/Co₃S₄ hollow nanocubes anchored on S‐doped graphene are synthesized for the first time via coprecipitation and hydrothermal methods. When applied as the anode for SIBs, the sample delivers a distinguished charge specific capacity of 1141.8 mAh g^?1 and there is no significant capacity decay (0.1 A g^?1 for 50 cycles). When the rate is increased to 0.5 A g^?1, it presents 845.7 mAh g^?1 after cycling 100 times. Furthermore, the composite also exhibits an ultrafast sodium storage capability where 392.9 mAh g^?1 can be obtained at 10 A g^?1 and the charging time is less than 3 min. The outstanding electrochemical properties can be ascribed to the enhancement of conductivity for the addition of S‐doped graphene and the existence of p–n junctions in the SnS₂/Co₃S₄ heterostructure. Moreover, the presence of mesopores between nanosheets can alleviate volume expansion during cycling as well as being beneficial for the migration of Na⁺.     

Nitrogen Doped γ‐Graphyne: A Novel Anode for High‐Capacity Rechargeable Alkali‐Ion Batteries

High energy density is the major demand for next‐generation rechargeable batteries, while the intrinsic low alkali metal adsorption of traditional carbon–based electrode remains the main challenge. Here, the mechanochemical route is proposed to prepare nitrogen doped γ‐graphyne (NGY) and its high capacity is demonstrated in lithium (LIBs)/sodium (SIBs) ion batteries. The sample delivers large reversible Li (1037 mAh g^?1) and Na (570.4 mAh g^?1) storage capacities at 100 mA g^?1 and presents excellent rate capabilities (526 mAh g^?1 for LIBs and 180.2 mAh g^?1 for SIBs) at 5 A g^?1. The superior Li/Na storage mechanisms of NGY are revealed by its 2D morphology evolution, quantitative kinetics, and theoretical calculations. The effects on the diffusion barriers (E_b) and adsorption energies (E_ad) of Li/Na atoms in NGY are also studied and imine‐N is demonstrated to be the ideal doping format to enhance the Li/Na storage performance. Besides, the Li/Na adsorption routes in NGY are optimized according to the experimental and the first‐principles calculation results. This work provides a facile way to fabricate high capacity electrodes in LIBs/SIBs, which is also instructive for the design of other heteroatomic doped electrodes.     

Multidimensional Synergistic Nanoarchitecture Exhibiting Highly Stable and Ultrafast Sodium‐Ion Storage

Conversion‐type anodes with multielectron reactions are beneficial for achieving a high capacity in sodium‐ion batteries. Enhancing the electron/ion conductivity and structural stability are two key challenges in the development of high‐performance sodium storage. Herein, a novel multidimensionally assembled nanoarchitecture is presented, which consists of V₂O₃ nanoparticles embedded in amorphous carbon nanotubes that are then coassembled within a reduced graphene oxide (rGO) network, this materials is denoted V₂O₃?C‐NTs?rGO. The selective insertion and multiphase conversion mechanism of V₂O₃ in sodium‐ion storage is systematically demonstrated for the first time. Importantly, the naturally integrated advantages of each subunit synergistically provide a robust structure and rapid electron/ion transport, as confirmed by in situ and ex situ transmission electron microscopy experiments and kinetic analysis. Benefiting from the synergistic effects, the V₂O₃?C‐NTs?rGO anode delivers an ultralong cycle life (72.3% at 5 A g^?1 after 15 000 cycles) and an ultrahigh rate capability (165 mAh g^?1 at 20 A g^?1, ≈30 s per charge/discharge). The synergistic design of the multidimensionally assembled nanoarchitecture produces superior advantages in energy storage.     

In Situ Carbon‐Doped Mo(Se0.85S0.15)2 Hierarchical Nanotubes as Stable Anodes for High‐Performance Sodium‐Ion Batteries

Sodium‐ion batteries (SIBs) are promising energy storage devices, but suffer from poor cycling stability and low rate capability. In this work, carbon doped Mo(Se_0.85S_0.15)₂ (i.e., Mo(Se_0.85S_0.15)₂:C) hierarchical nanotubes have been synthesized for the first time and serve as a robust and high‐performance anode material. The hierarchical nanotubes with diameters of 300 nm and wall thicknesses of 50 nm consist of numerous 2D layered nanosheets, and can act as a robust host for sodiation/desodiation cycling. The Mo(Se_0.85S_0.15)₂:C hierarchical nanotubes deliver a discharge capacity of 360 mAh g⁻¹ at a high current density of 2000 mA g⁻¹ and keep a 81.8% capacity retention compared to that at a current density of 50 mA g⁻¹, showing superior rate capability. Comparing with the second cycle discharge capacities, the nanotube anode can maintain capacities of 102.2%, 101.9%, and 97.8% after 100 cycles at current densities of 200, 500, and 1000 mA g⁻¹, respectively. This work demonstrates the best cycling performance and high‐rate sodium storage capabilities of MoSe₂ for SIBs to date. The hollow interior, hierarchical organization, layered structure, and carbon doping are beneficial for fast Na⁺‐ion and electron kinetics and are responsible for the stable cycling performance and high rate capabilities.     

Graphene‐Encapsulated FeS2 in Carbon Fibers as High Reversible Anodes for Na+/K+ Batteries in a Wide Temperature Range

Developing low cost, long life, and high capacity rechargeable batteries is a critical factor towards developing next‐generation energy storage devices for practical applications. Therefore, a simple method to prepare graphene‐coated FeS₂ embedded in carbon nanofibers is employed; the double protection from graphene coating and carbon fibers ensures high reversibility of FeS₂ during sodiation/desodiation and improved conductivity, resulting in high rate capacity and long‐term life for Na⁺ (305.5 mAh g^?1 at 3 A g^?1 after 2450 cycles) and K⁺ (120 mAh g^?1 at 1 A g^?1 after 680 cycles) storage at room temperature. Benefitting from the enhanced conductivity and protection on graphene‐encapsulated FeS₂ nanoparticles, the composites exhibit excellent electrochemical performance under low temperature (0 and ?20 °C), and temperature tolerance with stable capacity as sodium‐ion half‐cells. The Na‐ion full‐cells based on the above composites and Na₃V₂(PO₄)₃ can afford reversible capacity of 95 mAh g^?1 at room temperature. Furthermore, the full‐cells deliver promising discharge capacity (50 mAh g^?1 at 0 °C, 43 mAh g^?1 at ?20 °C) and high energy density at low temperatures. Density functional theory calculations imply that graphene coating can effectively decrease the Na⁺ diffusion barrier between FeS₂ and graphene heterointerface and promote the reversibility of Na⁺ storage in FeS₂, resulting in advanced Na⁺ storage properties.     

3D Graphene Networks Encapsulated with Ultrathin SnS Nanosheets@Hollow Mesoporous Carbon Spheres Nanocomposite with Pseudocapacitance‐Enhanced Lithium and Sodium Storage Kinetics

The lithium and sodium storage performances of SnS anode often undergo rapid capacity decay and poor rate capability owing to its huge volume fluctuation and structural instability upon the repeated charge/discharge processes. Herein, a novel and versatile method is described for in situ synthesis of ultrathin SnS nanosheets inside and outside hollow mesoporous carbon spheres crosslinked reduced graphene oxide networks. Thus, 3D honeycomb‐like network architecture is formed. Systematic electrochemical studies manifest that this nanocomposite as anode material for lithium‐ion batteries delivers a high charge capacity of 1027 mAh g^?1 at 0.2 A g^?1 after 100 cycles. Meanwhile, the as‐developed nanocomposite still retains a charge capacity of 524 mAh g^?1 at 0.1 A g^?1 after 100 cycles for sodium‐ion batteries. In addition, the electrochemical kinetics analysis verifies the basic principles of enhanced rate capacity. The appealing electrochemical performance for both lithium‐ion batteries and sodium‐ion batteries can be mainly related to the porous 3D interconnected architecture, in which the nanoscale SnS nanosheets not only offer decreased ion diffusion pathways and fast Li⁺/Na⁺ transport kinetics, but also the 3D interconnected conductive networks constructed from the hollow mesoporous carbon spheres and reduced graphene oxide enhance the conductivity and ensure the structural integrity.     

Flexible and Binder‐Free Electrodes of Sb/rGO and Na3V2(PO4)3/rGO Nanocomposites for Sodium‐Ion Batteries

Flexible power sources have shown great promise in next‐generation bendable, implantable, and wearable electronic systems. Here, flexible and binder‐free electrodes of Na₃V₂(PO₄)₃/reduced graphene oxide (NVP/rGO) and Sb/rGO nanocomposites for sodium‐ion batteries are reported. The Sb/rGO and NVP/rGO paper electrodes with high flexibility and tailorability can be easily fabricated. Sb and NVP nanoparticles are embedded homogenously in the interconnected framework of rGO nanosheets, which provides structurally stable hosts for Na‐ion intercalation and deintercalation. The NVP/rGO paper‐like cathode delivers a reversible capacity of 113 mAh g^?1 at 100 mA g^?1 and high capacity retention of ≈96.6% after 120 cycles. The Sb/rGO paper‐like anode gives a highly reversible capacity of 612 mAh g^?1 at 100 mA g^?1, an excellent rate capacity up to 30 C, and a good cycle performance. Moreover, the sodium‐ion full cell of NVP/rGO//Sb/rGO has been fabricated, delivering a highly reversible capacity of ≈400 mAh g^?1 at a current density of 100 mA g^?1 after 100 charge/discharge cycles. This work may provide promising electrode candidates for developing next‐generation energy‐storage devices with high capacity and long cycle life.     

S‐Doped Carbon Fibers Uniformly Embedded with Ultrasmall TiO2 for Na+/Li+ Storage with High Capacity and Long‐Time Stability

Building a rechargeable battery with high capacity, high energy density, and long lifetime contributes to the development of novel energy storage devices in the future. Although carbon materials are very attractive anode materials for lithium‐ion batteries (LIBs), they present several deficiencies when used in sodium‐ion batteries (SIBs). The choice of an appropriate structural design and heteroatom doping are critical steps to improve the capacity and stability. Here, carbon‐based nanofibers are produced by sulfur doping and via the introduction of ultrasmall TiO₂ nanoparticles into the carbon fibers (CNF‐S@TiO₂). It is discovered that the introduction of TiO₂ into carbon nanofibers can significantly improve the specific surface area and microporous volume for carbon materials. The TiO₂ content is controlled to obtain CNF‐S@TiO₂‐5 to use as the anode material for SIBs/LIBs with enhanced electrochemical performance in Na⁺/Li⁺ storage. During the charge/discharge process, the S‐doping and the incorporation of TiO₂ nanoparticles into carbon fibers promote the insertion/extraction of the ions and enhance the capacity and cycle life. The capacity of CNF‐S@TiO₂‐5 can be maintained at ≈300 mAh g^?1 over 600 cycles at 2 A g^?1 in SIBs. Moreover, the capacity retention of such devices is 94%, showing high capacity and good stability.     

Graphene‐Protected 3D Sb‐based Anodes Fabricated via Electrostatic Assembly and Confinement Replacement for Enhanced Lithium and Sodium Storage

Alloy anodes have shown great potential for next‐generation lithium‐ion batteries (LIBs) and sodium‐ion batteries (SIBs). However, these applications are still limited by inherent huge volume changes and sluggish kinetics. To overcome such limitations, graphene‐protected 3D Sb‐based anodes grown on conductive substrate are designed and fabricated by a facile electrostatic‐assembling and subsequent confinement replacement strategy. As binder‐free anodes for LIBs, the obtained electrode exhibits reversible capacities of 442 mAh g⁻¹ at 100 mA g⁻¹ and 295 mAh g⁻¹ at 1000 mA g⁻¹, and a capacity retention of above 90% (based on the 10th cycle) after 200 cycles at 500 mA g⁻¹. As for sodium storage properties, the reversible capacities of 517 mAh g⁻¹ at 50 mA g⁻¹ and 315 mAh g⁻¹ at 1000 mA g⁻¹, the capacity retention of 305 mAh g⁻¹ after 100 cycles at 300 mA g⁻¹ are obtained, respectively. Furthermore, the 3D architecture retains good structural integrity after cycling, confirming that the introduction of high‐stretchy and robust graphene layers can effectively buffer alloying anodes, and simultaneously provide sustainable contact and protection of the active materials. Such findings show its great potential as superior binder‐free anodes for LIBs and SIBs.     

Controllable Interlayer Spacing of Sulfur‐Doped Graphitic Carbon Nanosheets for Fast Sodium‐Ion Batteries

The electrochemical behaviors of current graphitic carbons are seriously restricted by its low surface area and insufficient interlayer spacing for sodium‐ion batteries. Here, sulfur‐doped graphitic carbon nanosheets are reported by utilizing sodium dodecyl sulfate as sulfur resource and graphitization additive, showing a controllable interlayer spacing range from 0.38 to 0.41 nm and a high specific surface area up to 898.8 m² g^?1. The obtained carbon exhibits an extraordinary electrochemical activity for sodium‐ion storage with a large reversible capacity of 321.8 mAh g^?1 at 100 mA g^?1, which can be mainly attributed to the expanded interlayer spacing of the carbon materials resulted from the S‐doping. Impressively, superior rate capability of 161.8 mAh g^?1 is reserved at a high current density of 5 A g^?1 within 5000 cycles, which should be ascribed to the fast surface‐induced capacitive behavior derived from its high surface area. Furthermore, the storage processes are also quantitatively evaluated, confirming a mixed storage mechanism of diffusion‐controlled intercalation behavior and surface‐induced capacitive behavior. This study provides a novel route for rationally designing various carbon‐based anodes with enhanced rate capability.     

Hierarchical Porous Nanosheets Constructed by Graphene‐Coated,Interconnected TiO2 Nanoparticles for Ultrafast Sodium Storage

Sodium‐ion batteries (SIBs) are considered promising next‐generation energy storage devices. However, a lack of appropriate high‐performance anode materials has prevented further improvements. Here, a hierarchical porous hybrid nanosheet composed of interconnected uniform TiO₂ nanoparticles and nitrogen‐doped graphene layer networks (TiO₂@NFG HPHNSs) that are synthesized using dual‐functional C₃N₄ nanosheets as both the self‐sacrificing template and hybrid carbon source is reported. These HPHNSs deliver high reversible capacities of 146 mA h g^?1 at 5 C for 8000 cycles, 129 mA h g^?1 at 10 C for 20 000 cycles, and 116 mA h g^?1 at 20 C for 10 000 cycles, as well as an ultrahigh rate capability up to 60 C with a capacity of 101 mA h g^?1. These results demonstrate the longest cyclabilities and best rate capability ever reported for TiO₂‐based anode materials for SIBs. The unprecedented sodium storage performance of the TiO₂@NFG HPHNSs is due to their unique composition and hierarchical porous 2D structure.     

Graphitic Carbon Nitride (g‐C3N4)‐Derived N‐Rich Graphene with Tuneable Interlayer Distance as a High‐Rate Anode for Sodium‐Ion Batteries

Heteroatom‐doped carbon materials with expanded interlayer distance have been widely studied as anodes for sodium‐ion batteries (SIBs). However, it remains unexplored to further enlarge the interlayer spacing and reveal the influence of heteroatom doping on carbon nanostructures for developing more efficient SIB anode materials. Here, a series of N‐rich few‐layer graphene (N‐FLG) with tuneable interlayer distance ranging from 0.45 to 0.51 nm is successfully synthesized by annealing graphitic carbon nitride (g‐C₃N₄) under zinc catalysis and selected temperature (T = 700, 800, and 900 °C). More significantly, the correlation between N dopants and interlayer distance of resultant N‐FLG‐T highlights the effect of pyrrolic N on the enlargement of graphene interlayer spacing, due to its stronger electrostatic repulsion. As a consequence, N‐FLG‐800 achieves the optimal properties in terms of interlayer spacing, nitrogen configuration and electronic conductivity. When used as an anode for SIBs, N‐FLG‐800 shows remarkable Na⁺ storage performance with ultrahigh rate capability (56.6 mAh g^?1 at 40 A g^?1) and excellent long‐term stability (211.3 mAh g^?1 at 0.5 A g^?1 after 2000 cycles), demonstrating the effectiveness of material design.     

MOF‐Derived Hollow Co9S8 Nanoparticles Embedded in Graphitic Carbon Nanocages with Superior Li‐Ion Storage

Novel electrode materials consisting of hollow cobalt sulfide nanoparticles embedded in graphitic carbon nanocages (HCSP?GCC) are facilely synthesized by a top‐down route applying room‐temperature synthesized Co‐based zeolitic imidazolate framework (ZIF‐67) as the template. Owing to the good mechanical flexibility and pronounced structure stability of carbon nanocages‐encapsulated Co₉S₈, the as‐obtained HCSP?GCC exhibit superior Li‐ion storage. Working in the voltage of 1.0?3.0 V, they display a very high energy density (707 Wh kg^?1), superior rate capability (reversible capabilities of 536, 489, 438, 393, 345, and 278 mA h g^?1 at 0.2, 0.5, 1, 2, 5, and 10C, respectively), and stable cycling performance (≈26% capacity loss after long 150 cycles at 1C with a capacity retention of 365 mA h g^?1). When the work voltage is extended into 0.01–3.0 V, a higher stable capacity of 1600 mA h g^?1 at a current density of 100 mA g^?1 is still achieved.     

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.     

Boosting Sodium Storage in TiO2 Nanotube Arrays through Surface Phosphorylation

Sodium‐ion batteries (SIBs) offer a promise of a scalable, low‐cost, and environmentally benign means of renewable energy storage. However, the low capacity and poor rate capability of anode materials present an unavoidable challenge. In this work, it is demonstrated that surface phosphorylated TiO₂ nanotube arrays grown on Ti substrate can be efficient anode materials for SIBs. Fabrication of the phosphorylated nanoarray film is based on the electrochemical anodization of Ti metal in NH₄F solution and subsequent phosphorylation using sodium hypophosphite. The phosphorylated TiO₂ nanotube arrays afford a reversible capacity of 334 mA h g^?1 at 67 mA g^?1, a superior rate capability of 147 mA h g^?1 at 3350 mA g^?1, and a stable cycle performance up to 1000 cycles. In situ X‐ray diffraction and transmission electron microscopy reveal the near‐zero strain response and robust mechanical behavior of the TiO₂ host upon (de)sodiation, suggesting its excellent structural stability in the Na⁺ storage application.     

Bismuth Nanoparticle@Carbon Composite Anodes for Ultralong Cycle Life and High‐Rate Sodium‐Ion Batteries

Bismuth has emerged as a promising anode material for sodium‐ion batteries (SIBs), owing to its high capacity and suitable operating potential. However, large volume changes during alloying/dealloying processes lead to poor cycling performance. Herein, bismuth nanoparticle@carbon (Bi@C) composite is prepared via a facile annealing method using a commercial coordination compound precursor of bismuth citrate. The composite has a uniform structure with Bi nanoparticles embedded within a carbon framework. The nanosized structure ensures a fast kinetics and efficient alleviation of stress/strain caused by the volume change, and the resilient and conductive carbon matrix provides an interconnected electron transportation pathway. The Bi@C composite delivers outstanding sodium‐storage performance with an ultralong cycle life of 30 000 cycles at a high current density of 8 A g^?1 and an excellent rate capability of 71% capacity retention at an ultrahigh current rate of 60 A g^?1. Even at a high mass loading of 11.5 mg cm^?2, a stable reversible capacity of 280 mA h g^?1 can be obtained after 200 cycles. More importantly, full SIBs by pairing with a Na₃V₂(PO₄)₃ cathode demonstrates superior performance. Combining the facile synthesis and the commercial precursor, the exceptional performance makes the Bi@C composite very promising for practical large‐scale applications.