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.     

Novel 2D Layered Molybdenum Ditelluride Encapsulated in Few‐Layer Graphene as High‐Performance Anode for Lithium‐Ion Batteries

Molybdenum ditelluride nanosheets encapsulated in few‐layer graphene (MoTe₂/FLG) are synthesized by a simple heating method using Te and Mo powder and subsequent ball milling with graphite. The as‐prepared MoTe₂/FLG nanocomposites as anode materials for lithium‐ion batteries exhibit excellent electrochemical performance with a highly reversible capacity of 596.5 mAh g^?1 at 100 mA g^?1, a high rate capability (334.5 mAh g^?1 at 2 A g^?1), and superior cycling stability (capacity retention of 99.5% over 400 cycles at 0.5 A g^?1). Ex situ X‐ray diffraction and transmission electron microscopy are used to explore the lithium storage mechanism of MoTe₂. Moreover, the electrochemical performance of a MoTe₂/FLG//0.35Li₂MnO₃·0.65LiMn_0.5Ni_0.5O₂ full cell is investigated, which displays a reversible capacity of 499 mAh g^?1 (based on the MoTe₂/FLG mass) at 100 mA g^?1 and a capacity retention of 78% over 50 cycles, suggesting the promising application of MoTe₂/FLG for lithium‐ion storage. First‐principles calculations exhibit that the lowest diffusion barrier (0.18 eV) for lithium ions along pathway III in the MoTe₂ layered structure is beneficial for improving the Li intercalation/deintercalation property.     

N‐Doped Carbon Nanofibers with Interweaved Nanochannels for High‐Performance Sodium‐Ion Storage

Although graphite materials have been applied as commercial anodes in lithium‐ion batteries (LIBs), there still remain abundant spaces in the development of carbon‐based anode materials for sodium‐ion batteries (SIBs). Herein, an electrospinning route is reported to fabricate nitrogen‐doped carbon nanofibers with interweaved nanochannels (NCNFs‐IWNC) that contain robust interconnected 1D porous channels, produced by removal of a Te nanowire template that is coelectrospun within carbon nanofibers during the electrospinning process. The NCNFs‐IWNC features favorable properties, including a conductive 1D interconnected porous structure, a large specific surface area, expanded interlayer graphite‐like spacing, enriched N‐doped defects and active sites, toward rapid access and transport of electrolyte and electron/sodium ions. Systematic electrochemical studies indicate that the NCNFs‐IWNC exhibits an impressively high rate capability, delivering a capacity of 148 mA h g^?1 at current density of as high as 10 A g^?1, and has an attractively stable performance over 5000 cycles. The practical application of the as‐designed NCNFs‐IWNC for a full SIBs cell is further verified by coupling the NCNFs‐IWNC anode with a FeFe(CN)₆ cathode, which displays a desirable cycle performance, maintaining acapacity of 97 mA h g^?1 over 100 cycles.     

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⁺.     

Glucose‐Induced Synthesis of 1T‐MoS2/C Hybrid for High‐Rate Lithium‐Ion Batteries

1T phase MoS₂ possesses higher conductivity than the 2H phase, which is a key parameter of electrochemical performance for lithium ion batteries (LIBs). Herein, a 1T‐MoS₂/C hybrid is successfully synthesized through facile hydrothermal method with a proper glucose additive. The synthesized hybrid material is composed of smaller and fewer‐layer 1T‐MoS₂ nanosheets covered by thin carbon layers with an enlarged interlayer spacing of 0.94 nm. When it is used as an anode material for LIBs, the enlarged interlayer spacing facilitates rapid intercalating and deintercalating of lithium ions and accommodates volume change during cycling. The high intrinsic conductivity of 1T‐MoS₂ also contributes to a faster transfer of lithium ions and electrons. Moreover, much smaller and fewer‐layer nanosheets can shorten the diffusion path of lithium ions and accelerate reaction kinetics, leading to an improved electrochemical performance. It delivers a high initial capacity of 920.6 mAh g^?1 at 1 A g^?1 and the capacity can maintain 870 mAh g^?1 even after 300 cycles, showing a superior cycling stability. The electrode presents a high rate performance as well with a reversible capacity of 600 mAh g^?1 at 10 A g^?1. These results show that the 1T‐MoS₂/C hybrid shows potential for use in high‐performance lithium‐ion batteries.     

High‐Performance Flexible Freestanding Anode with Hierarchical 3D Carbon‐Networks/Fe7S8/Graphene for Applicable Sodium‐Ion Batteries

Sodium‐ion batteries (SIBs) have gained tremendous interest for grid scale energy storage system and power energy batteries. However, the current researches of anode for SIBs still face the critical issues of low areal capacity, limited cycle life, and low initial coulombic efficiency for practical application perspective. To solve this issue, a kind of hierarchical 3D carbon‐networks/Fe₇S₈/graphene (CFG) is designed and synthesized as freestanding anode, which is constructed with Fe₇S₈ microparticles well‐welded on 3D‐crosslinked carbon‐networks and embedded in highly conductive graphene film, via a facile and scalable synthetic method. The as‐prepared freestanding electrode CFG represents high areal capacity (2.12 mAh cm^?2 at 0.25 mA cm^?2) and excellent cycle stability of 5000 cycles (0.0095% capacity decay per cycle). The assembled all‐flexible sodium‐ion battery delivers remarkable performance (high areal capacity of 1.42 mAh cm^?2 at 0.3 mA cm^?2 and superior energy density of 144 Wh kg^?1), which are very close to the requirement of practical application. This work not only enlightens the material design and electrode engineering, but also provides a new kind of freestanding high energy density anode with great potential application prospective for SIBs.     

Na2Ti6O13 Nanorods with Dominant Large Interlayer Spacing Exposed Facet for High‐Performance Na‐Ion Batteries

As the delegate of tunnel structure sodium titanates, Na₂Ti₆O₁₃ nanorods with dominant large interlayer spacing exposed facet are prepared. The exposed large interlayers provide facile channels for Na⁺ insertion and extraction when this material is used as anode for Na‐ion batteries (NIBs). After an activation process, this NIB anode achieves a high specific capacity (a capacity of 172 mAh g^?1 at 0.1 A g^?1) and outstanding cycling stability (a capacity of 109 mAh g^?1 after 2800 cycles at 1 A g^?1), showing its promising application on large‐scale energy storage systems. Furthermore, the electrochemical and structural characterization reveals that the expanded interlayer spacings should be in charge of the activation process, including the enhanced kinetics, the lowered apparent activation energy, and the increased capacity.     

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.     

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.     

Metal–Semiconductor Phase Twinned Hierarchical MoS2 Nanowires with Expanded Interlayers for Sodium‐Ion Batteries with Ultralong Cycle Life

Sodium‐ion batteries (SIBs) are considered a prospective candidate for large‐scale energy storage due to the merits of abundant sodium resources and low cost. However, a lack of suitable advanced anode materials has hindered further applications. Herein, metal–semiconductor mixed phase twinned hierarchical (MPTH) MoS₂ nanowires with an expanded interlayer (9.63 Å) are engineered and prepared using MoO₃ nanobelts as a self‐sacrificed template in the presence of a trace amount of (NH₄)₆Mo₇O₂₄·4H₂O as initiator. The greatly expanded interlayer spacing accelerates Na⁺ insertion/extraction kinetics, and the metal–semiconductor mixed phase enhances electron transfer ability and stabilizes electrode structure during cycling. Benefiting from the structural merits, the MPTH MoS₂ electrode delivers high reversible capacities of 200 mAh g^?1 at 0.1 A g^?1 for 200 cycles and 154 mAh g^?1 at 1 A g^?1 for 2450 cycles in the voltage range of 0.4–3.0 V. Strikingly, the electrode maintains 6500 cycles at a current density of 2 A g^?1, corresponding to a capacity retention of 82.8% of the 2nd cycle, overwhelming the all reported MoS₂ cycling results. This study provides an alternative strategy to boost SIB cycling performance in terms of reversible capacity by virtue of interlayer expansion and structure stability.     

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.     

Revealing the Simultaneous Effects of Conductivity and Amorphous Nature of Atomic‐Layer‐Deposited Double‐Anion‐Based Zinc Oxysulfide as Superior Anodes in Na‐Ion Batteries

Although sodium‐ion batteries (SIBs) are considered promising alternatives to their Li counterparts, they still suffer from challenges like slow kinetics of the sodiation process, large volume change, and inferior cycling stability. On the other hand, the presence of additional reversible conversion reactions makes the metal compounds the preferred anode materials over carbon. However, conductivity and crystallinity of such materials often play the pivotal role in this regard. To address these issues, atomic layer deposited double‐anion‐based ternary zinc oxysulfide (ZnOS) thin films as an anode material in SIBs are reported. Electrochemical studies are carried out with different O/(O+S) ratios, including O‐rich and S‐rich crystalline ZnOS along with the amorphous phase. Amorphous ZnOS with the O/(O+S) ratio of ≈0.4 delivers the most stable and considerably high specific (and volumetric) capacities of 271.9 (≈1315.6 mAh cm^?3) and 173.1 mAh g^?1 (≈837.7 mAh cm^?3) at the current densities of 500 and 1000 mA g^?1, respectively. A dominant capacitive‐controlled contribution of the amorphous ZnOS anode indicates faster electrochemical reaction kinetics. An electrochemical reaction mechanism is also proposed via X‐ray photoelectron spectroscopy analyses. A comparison of the cycling stability further establishes the advantage of this double‐anion‐based material over pristine ZnO and ZnS anodes.     

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.     

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.     

SnO2 Quantum Dots: Rational Design to Achieve Highly Reversible Conversion Reaction and Stable Capacities for Lithium and Sodium Storage

SnO₂ has been considered as a promising anode material for lithium‐ion batteries (LIBs) and sodium ion batteries (SIBs), but challenging as well for the low‐reversible conversion reaction and coulombic efficiency. To address these issues, herein, SnO₂ quantum dots (≈5 nm) embedded in porous N‐doped carbon matrix (SnO₂/NC) are developed via a hydrothermal step combined with a self‐polymerization process at room temperature. The ultrasmall size in quantum dots can greatly shorten the ion diffusion distance and lower the internal strain, improving the conversion reaction efficiency and coulombic efficiency. The rich mesopores/micropores and highly conductive N‐doped carbon matrix can further enhance the overall conductivity and buffer effect of the composite. As a result, the optimized SnO₂/NC‐2 composite for LIBs exhibits a high coulombic efficiency of 72.9%, a high discharge capacity of 1255.2 mAh g^?1 at 0.1 A g^?1 after 100 cycles and a long life‐span with a capacity of 753 mAh g^?1 after 1500 cycles at 1 A g^?1. The SnO₂/NC‐2 composite also displays excellent performance for SIBs, delivering a superior discharge capacity of 212.6 mAh g^?1 at 1 A g^?1 after 3000 cycles. These excellent results can be of visible significance for the size effect of the uniform quantum dots.     

Controllable N‐Doped CuCo2O4@C Film as a Self‐Supported Anode for Ultrastable Sodium‐Ion Batteries

Rational synthesis of flexible electrodes is crucial to rapid growth of functional materials for energy‐storage systems. Herein, a controllable fabrication is reported for the self‐supported structure of CuCo₂O₄ nanodots (≈3 nm) delicately inserted into N‐doped carbon nanofibers (named as 3‐CCO@C); this composite is first used as binder‐free anode for sodium‐ion batteries (SIBs). Benefiting from the synergetic effect of ultrasmall CuCo₂O₄ nanoparticles and a tailored N‐doped carbon matrix, the 3‐CCO@C composite exhibits high cycling stability (capacity of 314 mA h g^?1 at 1000 mA g^?1 after 1000 cycles) and high rate capability (296 mA h g^?1, even at 5000 mA g^?1). Significantly, the Na storage mechanism is systematically explored, demonstrating that the irreversible reaction of CuCo₂O₄, which decomposes to Cu and Co, happens in the first discharge process, and then a reversible reaction between metallic Cu/Co and CuO/Co₃O₄ occurrs during the following cycles. This result is conducive to a mechanistic study of highly promising bimetallic‐oxide anodes for rechargeable SIBs.     

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.     

High‐Performance Sodium‐Ion Battery Anode via Rapid Microwave Carbonization of Natural Cellulose Nanofibers with Graphene Initiator

Cellulose is a promising natural bio‐macromolecule due to its abundance, renewability and low cost. Here, a new method is developed to prepare pre‐sodiated carbonaceous anodes for sodium‐ion batteries (SIBs) from cellulose nanofibers (CNFs) under microwave irradiation for potential ultrafast and large‐scale manufacturing. While direct carbonization of CNFs through microwave treatment is usually impossible due to the weak microwave absorption of CNFs, it is found that a small amount of reduced graphene oxide (rGO) can act as an effective initiator. Microwaving rGO releases extremely high energy, giving rise to local ultrahigh temperature as well as ultrahigh heating rate, which then induces the fast carbonization of CNFs and the production of pre‐sodiated carbonaceous materials within seconds. The sodium in the carbonaceous materials, introduced from the carbonization of CNFs containing sodium‐ion carboxyl, offer favorable spaces for sodiation/desodiation, which improves the electrochemical performance of the sodium‐inserted carbonaceous anode. When the microwaved rGO‐CNF (MrGO‐CNF) is used as an anode for SIBs, a high initial capacity of 558 mAh g^?1 is delivered and the capacity of 340 mAh g^?1 remains after 200 cycles. The excellent reversible capacity and cycling stability indicate MrGO‐CNF a promising anode for sodium‐ion batteries.     

Pistachio‐Shuck‐Like MoSe2/C Core/Shell Nanostructures for High‐Performance Potassium‐Ion Storage

Potassium‐ion batteries (KIBs) have recently attracted intensive attention because of the abundant potassium resources and their low cost and high safety. However, the major challenge faced by KIBs lies in the lack of stable and high‐capacity materials for the intercalation/deintercalation of large‐size potassium ions. A unique pistachio‐shuck‐like MoSe₂/C core/shell nanostructure (PMC) is synthesized herein as an advanced anode for boosting the performance of KIBs. This PMC is featured with a few layers of molybdenum selenide as the core with an expanded interlayer spacing of ≈0.85 nm, facilitating the intercalation/deintercalation of K ions, and a thin amorphous carbon as the shell, which can confine the active molybdenum selenide nanosheets during cycling for maintaining the high structural stability. Most importantly, as a whole, the PMC has the advantages of reducing the surplus hollow interior space for improving its packing density and buffering the volume expansion during the K‐ion intercalation for further enhancing the stability. As a consequence, the PMC shows a very high capacity of 322 mAh g^?1 at 0.2 A g^?1 over 100 cycles, and can still remain 226 mAh g^?1 at 1.0 A g^?1 for a long period of 1000 cycles, which is among the best‐reported KIBs anodes.