Peapod-Like Carbon-Encapsulated Cobalt Chalcogenide Nanowires as Cycle-Stable and High-Rate Materials for Sodium-Ion Anodes

Na3V2(PO4)3: an advanced cathode for sodium-ion batteries

Sodium-ion batteries (SIBs) are considered to be the most promising electrochemical energy storage devices for large-scale grid and electric vehicle applications due to the advantages of resource abundance and cost-effectiveness. The electrochemical performance of SIBs largely relies on the intrinsic chemical properties of the cathodic materials. Among the various cathodes, rhombohedral Na3V2(PO4)3 (NVP), a typical sodium super ionic conductor (NASICON) compound, is very popular owing to its high Na+ mobility and firm structural stability. However, the relatively low electronic conductivity makes the theoretical capacity of NVP cathodes unviable even at low rates, not to mention the high rate of charging/discharging. This is a major drawback of NVPs, limiting their future large-scale applications. Herein, a comprehensive review of the recent progresses made in NVP fabrication has been presented, mainly including the strategies of developing NVP/carbon hybrid materials and elemental doping to improve the electronic conductivity of NVP cathodes and designing 3D porous architectures to enhance Na-ion transportation. Moreover, the application of NVP cathodic materials in Na-ion full batteries is summarized, too. Finally, some remarks are made on the challenges and perspectives for the future development of NVP cathodes.

Ultrafast Sodium Full Batteries Derived from XFe (X = Co, Ni, Mn) Prussian Blue Analogs

Exploring high-rate electrode materials with excellent kinetic properties is imperative for advanced sodium-storage systems. Herein, novel cubic-like XFe (X = Co, Ni, Mn) Prussian blue analogs (PBAs), as cathodes materials, are obtained through as-tuned ionic bonding, delivering improved crystallinity and homogeneous particles size. As expected, Ni-Fe PBAs show a capacity of 81 mAh g^-1 at 1.0 A g^-1 , mainly resulting from their physical-chemical stability, fast kinetics, and "zero-strain" insertion characteristics. Considering that the combination of elements incorporated with carbon may increase the rate of ion transfer and improve the lifetime of cycling stability, they are expected to derive binary metal-selenide/nitrogen-doped carbon as anodes. Among them, binary Ni_0.67 Fe_0.33 Se₂ coming from Ni-Fe PBAs shows obvious core-shell structure in a dual-carbon matrix, leading to enhanced electron interactions, electrochemical activity, and "metal-like" conductivity, which could retain an ultralong-term stability of 375 mAh g^-1 after 10 000 loops even at 10.0 A g^-1 . The corresponding full-cell Ni-Fe PBAs versus Ni_0.67 Fe_0.33 Se₂ deliver a remarkable Na-storage capacity of 302.2 mAh g^-1 at 1.0 A g^-1 . The rational strategy is anticipated to offer more possibilities for designing advanced electrode materials used in high-performance sodium-ion batteries.

Rattle-type porous Sn/C composite fibers with uniformly distributed nanovoids containing metallic Sn nanoparticles for high-performance anode materials in lithium-ion batteries

Rattle-type porous Sn/carbon (Sn/C) composite fibers with uniformly distributed nanovoids containing metallic Sn nanoparticles in void space surrounded by C walls (denoted as RT-Sn@C porous fiber) were prepared by electrospinning and subsequent facile heat-treatment. Highly concentrated polystyrene nanobeads used as a sacrificial template played a key role in the synthesis of the unique structured RT-Sn@C porous fiber. The RT-Sn@C porous fiber exhibited excellent long-term cycling and rate performances. The discharge capacity of the RT-Sn@C porous fiber at the 1000^th cycle was 675 mA h g^-1 at a high current density of 3.0 A g^-1. The RT-Sn@C porous fiber had final discharge capacities of 991, 924, 890, 848, 784, 717, 679, and 614 mA h g^-1 at current densities of 0.1, 0.2, 0.3, 0.5, 1.0, 2.0, 3.0, 5.0, and 10.0 A g^-1, respectively. The numerous void spaces, surrounding a Sn nanoparticle as the rattle-type particle, and the surrounding C could efficiently accommodate the volume changes of the Sn nanoparticles, improve the electrical conductivity, and enable efficient penetration of the liquid electrolyte into the structure.

Nanoflower-like N-doped C/CoS2 as high-performance anode materials for Na-ion batteries

Novel nanoflower-like N-doped C/CoS2 spheres assembled from 2D wrinkled CoS2 nanosheets were synthesized through a facile one-pot solvothermal method followed by sulfurization. Ascribed to the optimized 3D nanostructure and rational surface engineering, the unique hierarchical structure of the nanoflower-like C/CoS2 composites showed an excellent sodium ion storage capacity accompanied by high specific capacity, superior rate performance and long-term cycling stability. Specifically, the conductive interconnected wrinkled nanosheets create a number of mesoporous structures and thus can greatly release the mechanical stress caused by Na+ insertion/extraction. Besides, it was observed from the experiments that many extra defect vacancies and Na+ storage sites are introduced by the nitrogen doping process. It was also observed that the crosslinked 2D nanosheets can effectively reduce the diffusion lengths of sodium ions and electrons, resulting in an outstanding rate performance (>700 mA h g-1 at 1 A g-1 and 458 mA h g-1 at even 10 A g-1) and extraordinary cycling stability (698 mA h g-1 at 1 A g-1 after 500 cycles). The results provide a facile approach to fabricate promising anode materials for high-performance sodium-ion batteries (SIBs).

Double-Morphology CoS2 Anchored on N-Doped Multichannel Carbon Nanofibers as High-Performance Anode Materials for Na-Ion Batteries

Na-ion batteries (NIBs) have attracted increasing attention given the fact that sodium is relatively more plentiful and affordable than lithium for sustainable and large-scale energy storage systems. However, the shortage of electrode materials with outstanding comprehensive properties has limited the practical implementations of NIBs. Among all the discovered anode materials, transition-metal sulfide has been proven as one of the most competitive and promising ones due to its excellent redox reversibility and relatively high theoretical capacity. In this study, double-morphology N-doped CoS₂/multichannel carbon nanofibers composites (CoS₂/MCNFs) are precisely designed, which overcome common issues such as the poor cycling life and inferior rate performance of CoS₂ electrodes. The conductive 3D interconnected multichannel nanostructure of CoS₂/MCNFs provides efficient buffer zones for the release of mechanical stresses from Na⁺ ions intercalation/deintercalation. The synergy of the diverse structural features enables a robust frame and a rapid electrochemical reaction in CoS₂/MCNFs anode, resulting in an impressive long-term cycling life of 900 cycles with a capacity of 620 mAh g^-1 at 1 A g^-1 (86.4% theoretical capacity) and a surprisingly high-power output. The proposed design in this study provides a rational and novel thought for fabricating electrode materials.

Recent Advances on Black Phosphorus for Energy Storage, Catalysis, and Sensor Applications

As a new type of 2D semiconductor, black phosphorus (BP) possesses high charge-carrier mobility and theoretical capacity, thickness-dependent bandgap, and anisotropic structure, which has attracted tremendous attention since early 2014. To explore its full application in all aspects, studies based on BP nanostructures are swiftly expanding from the electronic field to energy storage and even biochemistry. The mechanism and application of BP in Li-/Na-ion battery anodes, oxygen evolution reaction/hydrogen evolution reaction catalysis, photocatalytic hydrogen production, and selective sensors are summarized. Based on the solid research on this topic, feasible improvements and constructive suggestions regarding these four fields are put forward.

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

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

Rational Design of Hierarchical Nanotubes through Encapsulating CoSe2 Nanoparticles into MoSe2/C Composite Shells with Enhanced Lithium and Sodium Storage Performance

Transition-metal diselenides have been extensively studied as desirable anode candidates for both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) because of their high theoretical capacities. However, it is of great challenge to achieve satisfactory cycling performance, especially for larger sodium ion storage, originated from electrode deterioration upon large volume change. Herein, we reported the construction of hierarchical tubular hybrid nanostructures through encapsulating CoSe₂ nanoparticles into MoSe₂/C composite shells via a simple two-step strategy including a hydrothermal method followed by vapor-phase selenization process. The unique tubular structure enables the highly reversible Li/Na storage with high specific capacity, enhanced cycling stability, and superior rate performance. It is indicated that the contribution of partial pseudocapacitive behavior greatly improves the rate capability for SIBs, where a high capacity retention of 81.5% can be obtained when the current densities range from 0.1 to 3 A g^-1 (460 mA h g^-1 at 0.1 A g^-1 vs 379 mA h g^-1 at 3 A g^-1). This work provides an effective design rationale on transition-metal diselenide-based tubular nanostructures as superior hosts for both Li and Na ions, which could push forward the development of practical applications of transition-metal diselenide-based anodes in LIBs and SIBs.

Highly Porous FeS/Carbon Fibers Derived from Fe-Carrageenan Biomass: High-capacity and Durable Anodes for Sodium-Ion Batteries

The nanostructured metal sulfides have been reported as promising anode materials for sodium-ion batteries (SIBs) due to their high theoretical capacities but have suffered from the unsatisfactory electronic conductivity and poor structural stability during a charge/discharge process, thus limiting their applications. Herein, the one-dimensional (1D) porous FeS/carbon fibers (FeS/CFs) micro/nanostructures are fabricated through facile pyrolysis of double-helix-structured Fe-carrageenan fibers. The FeS nanoparticles are in situ formed by interacting with sulfur-containing group of natural material ι-carrageenan and uniformly embedded in the unique 1D porous carbon fibrous matrix, significantly enhancing the sodium-ion storage performance. The obtained FeS/CFs with optimized sodium storage performance benefits from the appropriate carbon content (20.9 wt %). The composite exhibits high capacity and excellent cycling stability (283 mAh g^-1 at current density of 1 A g^-1 after 400 cycles) and rate performance (247 mAh g^-1 at 5 A g^-1). This work provides a simple strategy to construct 1D porous FeS/CFs micro/nanostructures as high-performance anode materials for SIBs via a unique sustainable and environmentally friendly way.

Rapid Amorphization in Metastable CoSeO3·H2O Nanosheets for Ultrafast Lithiation Kinetics

The realization of high-performance anode materials with high capacity at fast lithiation kinetics and excellent cycle stability remains a significant but critical challenge for high-power applications such as electric vehicles. Two-dimensional nanostructures have attracted considerable research interest in electrochemical energy storage devices owing to their intriguing surface effect and significantly decreased ion-diffusion pathway. Here we describe rationally designed metastable CoSeO₃·H₂O nanosheets synthesized by a facile hydrothermal method for use as a Li ion battery anode. This crystalline nanosheet can be steadily converted into amorphous phase at the beginning of the first Li⁺ discharge cycling, leading to ultrahigh reversible capacities of 1100 and 515 mAh g^-1 after 1000 cycles at a high rate of 3 and 10 A g^-1, respectively. The as-obtained amorphous structure experiences an isotropic stress, which can significantly reduce the risk of fracture during electrochemical cycling. Our study offers a precious opportunity to reveal the ultrafast lithiation kinetics associated with the rapid amorphization mechanism in layered cobalt selenide nanosheets.

Pseudocapacitance-boosted ultrafast Na storage in a pie-like FeS@C nanohybrid as an advanced anode material for sodium-ion full batteries

In order to develop promising anode materials for sodium-ion batteries (SIBs), a novel pie-like FeS@C (P-FeS@C) nanohybrid, in which all ultrasmall FeS nanocrystals (NCs) are completely embedded into the carbon network and sealed by a protective carbon shell, has been prepared. The unique pie-like structure can effectively speed up the kinetics of electrode reactions, while the carbon shell stabilizes the FeS NCs inside. Studies show that the electrochemical reaction processes of P-FeS@C electrodes are dominated by the pseudocapacitive behavior, leading to an ultrafast Na+-insertion/extraction reaction. Hence, the prepared P-FeS@C nanohybrid exhibits superior Na-storage properties especially high rate capability in half cells. For example, it can deliver reversible capacities of 555.1 mA h g-1 at 0.2 A g-1 over 150 cycles and about 60.4 mA h g-1 at 80 A g-1 (an ultrahigh current density even higher than that of the capacitor test). Furthermore, an advanced P-FeS@C//Na3V2(PO4)2O2F full cell has been assembled out, which delivers a stable specific capacity of 441.2 mA h g-1 after 80 cycles at 0.5 A g-1 with a capacity retention of 91.8%.

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

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

Ultrafine Co1-xS nanoparticles embedded in a nitrogen-doped porous carbon hollow nanosphere composite as an anode for superb sodium-ion batteries and lithium-ion batteries

Cobalt sulfides are attractive as intriguing candidates for anodes in SIBs and LIBs owing to their unique chemical and physical properties. In this study, a precursor of Co_1-xS with a uniform and hollow nanospherical architecture is obtained with a high yield via a mild solvothermal method in the presence of 2-methylimidazole at first. Then, Co_1-xS, Co_1-xS/C (ultrafine Co_1-xS nanoparticles embedded in the shells of the nitrogen-doped porous carbon hollow nanosphere), and Co_1-xS@C (Co_1-xS nanoparticles entirely covered by an external amorphous carbon layer) were selectively fabricated via direct calcination or PPy coating & calcination of the obtained precursor. Co_1-xS/C shows best electrochemical performance than the other two materials as anodes for sodium-ion batteries (SIBs). Besides the excellent rate performance, a high reversible discharge capacity of 320 mA g^-1 can be retained after 130 cycles at 1 A g^-1. The impressive performance may be attributed to the unique structure, higher conductivity, and more active sites of Co_1-xS/C. In addition, 559 mA h g^-1 was maintained after 100 cycles at 500 mA g^-1 when the Co_1-xS/C composite was applied as an anode in lithium-ion batteries (LIBs). The high reversible capacity, excellent cycle stability combined with the facile synthesis procedure render Co_1-xS/C a prospective anode material for rechargeable batteries.

Ultrahigh Rate and Long-Life Sodium-Ion Batteries Enabled by Engineered Surface and Near-Surface Reactions

To achieve the high-power sodium-ion batteries, the solid-state ion diffusion in the electrode materials is a highly concerned issue and needs to be solved. In this study, a simple and effective strategy is reported to weaken and degrade this process by engineering the intensified surface and near-surface reactions, which is realized by making use of a sandwich-type nanoarchitecture composed of graphene as electron channels and few-layered MoS₂ with expanded interlayer spacing. The unique 2D sheet-shaped hierarchical structure is capable of shortening the ion diffusion length, while the few-layered MoS₂ with expanded interlayer spacing has more accessible surface area and the decreased ion diffusion resistance, evidenced by the smaller energy barriers revealed by the density functional theory calculations. Benefiting from the shortened ion diffusion distance and enhanced electron transfer capability, a high ratio of surface or near-surface reactions is dominated at a high discharge/charge rate. As such, the composites exhibit the high capacities of 152 and 93 mA h g^-1 at 30 and 50 A g^-1 , respectively. Moreover, a high reversible capacity of 684 mA h g^-1 and an excellent cycling stability up to 4500 cycles can be delivered. The outstanding performance is attributed to the engineered structure with increased contribution of surface or near-surface reactions.

A Scalable Strategy To Develop Advanced Anode for Sodium-Ion Batteries: Commercial Fe3O4-Derived Fe3O4@FeS with Superior Full-Cell Performance

A novel core-shell Fe₃O₄@FeS composed of Fe₃O₄ core and FeS shell with the morphology of regular octahedra has been prepared via a facile and scalable strategy via employing commercial Fe₃O₄ as the precursor. When used as anode material for sodium-ion batteries (SIBs), the prepared Fe₃O₄@FeS combines the merits of FeS and Fe₃O₄ with high Na-storage capacity and superior cycling stability, respectively. The optimized Fe₃O₄@FeS electrode shows ultralong cycle life and outstanding rate capability. For instance, it remains a capacity retention of 90.8% with a reversible capacity of 169 mAh g^-1 after 750 cycles at 0.2 A g^-1 and 151 mAh g^-1 at a high current density of 2 A g^-1, which is about 7.5 times in comparison to the Na-storage capacity of commercial Fe₃O₄. More importantly, the prepared Fe₃O₄@FeS also exhibits excellent full-cell performance. The assembled Fe₃O₄@FeS//Na₃V₂(PO₄)₂O₂F sodium-ion full battery gives a reversible capacity of 157 mAh g^-1 after 50 cycles at 0.5 A g^-1 with a capacity retention of 92.3% and the Coulombic efficiency of around 100%, demonstrating its applicability for sodium-ion full batteries as a promising anode. Furthermore, it is also disclosed that such superior electrochemical properties can be attributed to the pseudocapacitive behavior of FeS shell as demonstrated by the kinetics studies as well as the core-shell structure. In view of the large-scale availability of commercial precursor and ease of preparation, this study provide a scalable strategy to develop advanced anode materials for SIBs.

An open holey structure enhanced rate capability in a NaTi2(PO4)3/C nanocomposite and provided ultralong-life sodium-ion storage

Sodium-ion battery (SIB) technology is competitive in the fields of transportation and grid storage, which require electrode materials showing rapid energy conversion (high rate capability) and long cycle life. In this work, a NaTi₂(PO₄)₃/C (NTP/C) nanocomposite with an open holey-structured framework was successfully prepared for the first time using a solvothermal reaction followed by pyrolysis. The nanocomposite realized fast sodium-ion transport and thus preferable battery performances. Within the wide rate range of 0.5-50C, only a very small decrease in capacity from 124 to 120 mA h g^-1 was observed. A high discharge capacity of 103 mA h g^-1 (88.3% retention of the 1st cycle) was delivered even after 10 000 cycles at an ultrahigh rate of 50C without any obvious morphological change and without structural pulverization. Forming open channels for ion transport proved to contribute to such performance enhancement and therefore has the potential to become a universal model for the development of sustainable electrode materials in SIBs and other battery systems.

Heterogeneous Ti3SiC2@C-Containing Na2Ti7O15 Architecture for High-Performance Sodium Storage at Elevated Temperatures

Rational design of heterogeneous electrode materials with hierarchical architecture is a potential approach to significantly improve their energy densities. Herein, we report a tailored microwave-assisted synthetic strategy to create heterogeneous hierarchical Ti₃SiC₂@C-containing Na₂Ti₇O₁₅ (MAX@C-NTO) composites as potential anode materials for high-performance sodium storage in a wide temperature range from 25 to 80 °C. This composite delivers first reversible capacities of 230 mAh g^-1 at 200 mA g^-1 and 149 mAh g^-1 at 3000 mA g^-1 at 25 °C. A high capacity of ∼93 mAh g^-1 without any apparent decay even after more than 10 000 cycles is obtained at an ultrahigh current density of 10 000 mA g^-1. Moreover, both a high reversible capacity and an ultralong durable stability are achieved below 60 °C for the same composites, wherein a 75.2% capacity retention (∼120 mAh g^-1 at 10 000 mA g^-1) is achieved after 3000 cycles at 60 °C. To the best of our knowledge, both the sodium storage performances and the temperature tolerances outperform those of all the Ti-based sodium storage materials reported so far. The superior sodium storage performances of the as-synthesized composites are attributed to the heterogeneous core-shell architecture, which not only provides fast kinetics by high pseudocapacitance but also prolongs cycling life by preventing particle agglomeration and facilitates the transportation of electrons and sodium ions by large micro/mesopore structure.

The nanoscale circuitry of battery electrodes

Developing high-performance, affordable, and durable batteries is one of the decisive technological tasks of our generation. Here, we review recent progress in understanding how to optimally arrange the various necessary phases to form the nanoscale structure of a battery electrode. The discussion begins with design principles for optimizing electrode kinetics based on the transport parameters and dimensionality of the phases involved. These principles are then used to review and classify various nanostructured architectures that have been synthesized. Connections are drawn to the necessary fabrication methods, and results from in operando experiments are highlighted that give insight into how electrodes evolve during battery cycling.

Constructing hierarchical sulfur-doped nitrogenous carbon nanosheets for sodium-ion storage

Hierarchical sulfur-doped nitrogenous carbon (S/NC) and nitrogenous carbon (NC) nanosheets are successfully fabricated by carbonization of their corresponding precursor polymers which are synthesized through the polymerization reaction of dianhydride and multi-amine compounds. Hierarchical S/NC nanosheets deliver greatly enhanced reversible capacity, compared with hierarchical NC nanosheets, of 280 mAh g^-1 at a current density of 100 mA g^-1 after 300 cycles. It is found that the introduction of sulfur species in carbon skeleton results in increasing the turbostratic structures, rather than enlarging the interlayer distances, for boosting the specific capacity of sodium-ion storage. The turbostratic structures and sulfur dopant existed in the carbon can offer more active sites for the sodium-ion storage. Carbon-based materials doped with sulfur are capable of improving the sodium-ion storage property, which can broaden the horizon of designing a string of outstanding carbon materials for the future energy storage technologies.

Ni2 P@Carbon Core-Shell Nanoparticle-Arched 3D Interconnected Graphene Aerogel Architectures as Anodes for High-Performance Sodium-Ion Batteries

To alleviate large volume change and improve poor electrochemical reaction kinetics of metal phosphide anode for sodium-ion batteries, for the first time, an unique Ni₂ P@carbon/graphene aerogel (GA) 3D interconnected porous architecture is synthesized through a solvothermal reaction and in situ phosphorization process, where core-shell Ni₂ P@C nanoparticles are homogenously embedded in GA nanosheets. The synergistic effect between components endows Ni₂ P@C/GA electrode with high structural stability and electrochemical activity, leading to excellent electrochemical performance, retaining a specific capacity of 124.5 mA h g^-1 at a current density of 1 A g^-1 over 2000 cycles. The robust 3D GA matrix with abundant open pores and large surface area can provide unblocked channels for electrolyte storage and Na⁺ transfer and make fully close contact between the electrode and electrolyte. The carbon layers and 3D GA together build a 3D conductive matrix, which not only tolerates the volume expansion as well as prevents the aggregation and pulverization of Ni₂ P nanoparticles during Na⁺ insertion/extraction processes, but also provides a 3D conductive highway for rapid charge transfer processes. The present strategy for phosphides via in situ phosphization route and coupling phosphides with 3D GA can be extended to other novel electrodes for high-performance energy storage devices.

Bridging Covalently Functionalized Black Phosphorus on Graphene for High-Performance Sodium-Ion Battery

Black phosphorus (BP) has recently aroused researchers' great interest as promising anode material for sodium-ion battery (SIB), owing to its high theoretical capacity (2596 mAh g^-1) and good electric conductivity (about 300 S m^-1). However, the large volume variation during electrochemical cycling makes it difficult to use for practical applications. Herein, the reversible performance of BP in SIB is significantly enhanced by bridging covalently functionalized BP on graphene. The enhanced interaction between the chemical functionalized BP and graphene improves the stability of BP during long-cycle running of SIB. The bridging reduces the surface energy and increases thickness of BP available for enlarging the channel between BP nanosheet and graphene. The enlarged channel stores more sodium ions for improving cycle performance. Significantly, two types of phosphorus-carbon bond are first detected during experimental analysis. Benefiting from the strategy, the BP-based SIB anode exhibits 1472 mAh g^-1 specific capacity at 0.1 A g^-1 in the 50th cycle and 650 mAh g^-1 at 1 A g^-1 after 200 cycles.

CoS2 Nanoparticles Wrapping on Flexible Freestanding Multichannel Carbon Nanofibers with High Performance for Na-Ion Batteries

Exploration for stable and high-powered electrode materials is significant due to the growing demand for energy storage and also challengeable to the development and application of Na-ion batteries (NIBs). Among all promising electrode materials for NIBs, transition-mental sulfides have been identified as potential candidates owing to their distinct physics-chemistry characteristics. In this work, CoS₂ nanomaterials anchored into multichannel carbon nanofibers (MCNFs), synthesized via a facile solvothermal method with a sulfidation process, are studied as flexible free-standing electrode materials for NIBs. CoS₂ nanoparticles uniformly distributed in the vertical and horizontal multichannel networks. Such nanoarchitecture can not only support space for volume expansion of CoS₂ during discharge/charge process, but also facilitate ion/electron transport along the interfaces. In particular, the CoS₂@MCNF electrode delivers an impressively high specific capacity (537.5 mAh g^-1 at 0.1 A g^-1), extraordinarily long-term cycling stability (315.7 mAh g^-1 at at 1 A g^-1 after 1000 cycles), and excellent rate capacity (537.5 mAh g^-1 at 0.1 A g^-1 and 201.9 mAh g^-1 at 10 A g^-1) for sodium storage. Free-standing CoS₂@MCNF composites with mechanical flexibility provide a promising electrode material for high-powered NIBs and flexible cells.

Graphene Decorated by Indium Sulfide Nanoparticles as High-Performance Anode for Sodium-Ion Batteries

We report a highly performing anode material for sodium-ion batteries (SIBs) composed of graphene decorated by indium sulfide (In₂S₃). The composite is synthesized by a facile hydrothermal pathway with subsequent annealing and is characterized by defined structure and well-tailored morphology, as is indeed demonstrated by X-ray diffraction and spectroscopy as well as high-resolution microscopy. These optimal characteristics allow the electrode to perform remarkably in sodium cell by achieving a maximum specific capacity as high as 620 mAh g^-1 and the still-relevant value of 335 mAh g^-1 at an extremely high current (i.e., 5 A g^-1). The high storage capacity, the long cycle life, and the impressive rate capability of the composite may be attributed to the synergetic effect between uniform In₂S₃ nanoparticles and the graphene matrix. These features suggest that the In₂S₃-graphene is a viable choice for application as an anode material in high-performance SIBs.

Capillary-Induced Ge Uniformly Distributed in N-Doped Carbon Nanotubes with Enhanced Li-Storage Performance

Germanium (Ge) is a prospective anode material for lithium-ion batteries, as it possesses large theoretical capacity, outstanding lithium-ion diffusivity, and excellent electrical conductivity. Ge suffers from drastic capacity decay and poor rate performance, however, owing to its low electrical conductivity and huge volume expansion during cycling processes. Herein, a novel strategy has been developed to synthesize a Ge@N-doped carbon nanotubes (Ge@N-CNTs) composite with Ge nanoparticles uniformly distributed in the N-CNTs by using capillary action. This unique structure could effectively buffer large volume expansion. When evaluated as an anode material, the Ge@N-CNTs demonstrate enhanced cycling stability and excellent rate capabilities.

Emerging Prototype Sodium-Ion Full Cells with Nanostructured Electrode Materials

Due to steadily increasing energy consumption, the demand of renewable energy sources is more urgent than ever. Sodium-ion batteries (SIBs) have emerged as a cost-effective alternative because of the earth abundance of Na resources and their competitive electrochemical behaviors. Before practical application, it is essential to establish a bridge between the sodium half-cell and the commercial battery from a full cell perspective. An overview of the major challenges, most recent advances, and outlooks of non-aqueous and aqueous sodium-ion full cells (SIFCs) is presented. Considering the intimate relationship between SIFCs and electrode materials, including structure, composition and mutual matching principle, both the advance of various prototype SIFCs and the electrochemistry development of nanostructured electrode materials are reviewed. It is noted that a series of SIFCs combined with layered oxides and hard carbon are capable of providing a high specific gravimetric energy above 200 Wh kg^-1 , and an NaCrO₂ //hard carbon full cell is able to deliver a high rate capability over 100 C. To achieve industrialization of SIBs, more systematic work should focus on electrode construction, component compatibility, and battery technologies.

Nontopotactic Reaction in Highly Reversible Sodium Storage of Ultrathin Co9 Se8 /rGO Hybrid Nanosheets

Transition metal chalcogenide with tailored nanosheet architectures with reduced graphene oxide (rGO) for high performance electrochemical sodium ion batteries (SIBs) are presented. Via one-step oriented attachment growth, a facile synthesis of Co₉ Se₈ nanosheets anchored on rGO matrix nanocomposites is demonstrated. As effective anode materials of SIBs, Co₉ Se₈ /rGO nanocomposites can deliver a highly reversible capacity of 406 mA h g^-1 at a current density of 50 mA g^-1 with long cycle stability. It can also deliver a high specific capacity of 295 mA h g^-1 at a high current density of 5 A g^-1 indicating its high rate capability. Furthermore, ex situ transmission electron microscopy observations provide insight into the reaction path of nontopotactic conversion in the hybrid anode, revealing the highly reversible conversion directly between the hybrid Co₉ Se₈ /rGO and Co nanoparticles/Na₂ Se matrix during the sodiation/desodiation process. In addition, it is experimentally demonstrated that rGO plays significant roles in both controllable growth and electrochemical conversion processes, which can not only modulate the morphology of the product but also tune the sodium storage performance. The investigation on hybrid Co₉ Se₈ /rGO nanosheets as SIBs anode may shed light on designing new metal chalcogenide materials for high energy storage system.

Coordination of Surface-Induced Reaction and Intercalation: Toward a High-Performance Carbon Anode for Sodium-Ion Batteries

Oxygen-rich carbon material is successfully fabricated from a porous carbon and evaluated as anode for sodium-ion battery. With the strategy of optimal combination of fast surface redox reaction and reversible intercalation, the oxygen-rich carbon anode exhibits a large reversible capacity (447 mAh g^-1 at 0.2 A g^-1), high rate capability (172 mAh g^-1 at 20 A g^-1), and excellent cycling stability.

Confined Amorphous Red Phosphorus in MOF-Derived N-Doped Microporous Carbon as a Superior Anode for Sodium-Ion Battery

Red phosphorus (P) has attracted intense attention as promising anode material for high-energy density sodium-ion batteries (NIBs), owing to its high sodium storage theoretical capacity (2595 mAh g^-1 ). Nevertheless, natural insulating property and large volume variation of red P during cycling result in extremely low electrochemical activity, leading to poor electrochemical performance. Herein, the authors demonstrate a rational strategy to improve sodium storage performance of red P by confining nanosized amorphous red P into zeolitic imidazolate framework-8 (ZIF-8) -derived nitrogen-doped microporous carbon matrix (denoted as P@N-MPC). When used as anode for NIBs, the P@N-MPC composite displays a high reversible specific capacity of ≈600 mAh g^-1 at 0.15 A g^-1 and improved rate capacity (≈450 mAh g^-1 at 1 A g^-1 after 1000 cycles with an extremely low capacity fading rate of 0.02% per cycle). The superior sodium storage performance of the P@N-MPC is mainly attributed to the novel structure. The N-doped porous carbon with sub-1 nm micropore facilitates the rapid diffusion of organic electrolyte ions and improves the conductivity of the encapsulated red P. Furthermore, the porous carbon matrix can buffer the volume change of red P during repeat sodiation/desodiation process, keeping the structure intact after long cycle life.

Highly Reversible and Durable Na Storage in Niobium Pentoxide through Optimizing Structure, Composition, and Nanoarchitecture

Amorphous, hydrogenated, and self-ordered nanoporous Nb₂ O₅ films serve as an excellent binder-free electrode for sodium batteries, affording a high and sustainable capacity delivery and robust high-rate capability. This collaborative material engineering of structural order (amorphization), composition (hydrogenation), and architecture (ordered nanopore) opens up new possibilities to develop an energy storage solution that is more accessible, sustainable, and producible.

Sequential partial ion exchange synthesis of composite Ni3S2/Co9S8/NiSe nanoarrays with a lavender-like hierarchical morphology

A hierarchical Ni@Ni₃S₂/Co₉S₈/NiSe composite through sequential partial ion exchange for supercapacitor design.

Fabrication of Co@SiO2@C/Ni submicrorattles as highly efficient catalysts for 4-nitrophenol reduction

The Co@SiO₂@C/Ni magnetic composites have been synthesized by an extended Stöber method combined with a carbonization process.

A facile approach for graphdiyne preparation under atmosphere for an advanced battery anode

An explosion approach was developed for efficiently preparing graphdiynes (GDYs) at 120 °C in air without any metal catalyst.

Exploration of Ca0.5Ti2(PO4)3@carbon Nanocomposite as the High-Rate Negative Electrode for Na-Ion Batteries

Exploring suitable electrode materials with high specific capacity and high-rate capability is a challenging goal for the development of Na-ion batteries. Here, we report a NASICON-structured compound, Ca_0.5Ti₂(PO₄)₃, with respect to its synthesis and electrochemical properties. The electrode is found to enable fast Na⁺ ion diffusion owing to the rich crystallographic vacancies, affording a reversible capacity of 264 mA h g^-1 between 3.0 and 0.01 V. In particular, the hybrid Ca_0.5Ti₂(PO₄)₃@carbon exhibits remarkable rate performance with a discharge capacity of nearly 45 mA h g^-1 at a current density of 20 A g^-1, which is attributed to the pseudocapacitive effect.