Densified Metallic MoS2/Graphene Enabling Fast Potassium‐Ion Storage with Superior Gravimetric and Volumetric Capacities

The potassium‐ion battery (PIB) is an attractive energy storage device that possesses the potential advantages of high energy density and low cost. Herein, a pure 1T‐MoS₂ is synthesized on graphene oxide and assembled into a hydrogel. The hydrogel is further tightened to a compact 1T‐MoS₂/graphene (CTMG) bulk by a densifying strategy of capillary tension. When employed as an anode for PIBs, the CTMG electrode can store K⁺ through reversible intercalation and conversion electrochemistry, accompanied with fast kinetics since the 1T‐MoS₂ induces a pseudocapacitive storage mechanism and the extraordinary K⁺ transportation ability. Consequently, the CTMG electrode delivers the high and reversible rate capacities of 511 and 327 mAh g^‐1 at 0.1 and 1 A g^‐1, respectively. Moreover, the compact architecture reduces the electrode thickness by ≈33% enabling a high volumetric capacity (512 mAh cm^‐3 at 0.1 A g^‐1 after 100 cycles), as well as holding a promising application in thick electrode.     

Layered P2‐Type K0.65Fe0.5Mn0.5O2 Microspheres as Superior Cathode for High‐Energy Potassium‐Ion Batteries

Potassium‐ion batteries have been regarded as the potential alternatives to lithium‐ion batteries (LIBs) due to the low cost, earth abundance, and low potential of K (?2.936 vs standard hydrogen electrode (SHE)). However, the lack of low‐cost cathodes with high energy density and long cycle life always limits its application. In this work, high‐energy layered P2‐type hierarchical K_0.65Fe_0.5Mn_0.5O₂ (P2‐KFMO) microspheres, assembled by the primary nanoparticles, are fabricated via a modified solvent‐thermal method. Benefiting from the unique microspheres with primary nanoparticles, the K⁺ intercalation/deintercalation kinetics of P2‐KFMO is greatly enhanced with a stabilized cathodic electrolyte interphase on the cathode. The P2‐KFMO microsphere presents a highly reversible potassium storage capacity of 151 mAh g^?1 at 20 mA g^?1, fast rate capability of 103 mAh g^?1 at 100 mA g^?1, and long cycling stability with 78% capacity retention after 350 cycles. A full cell with P2‐KFMO microspheres as cathode and hard carbon as anode is constructed, which exhibits long‐term cycling stability (>80% of retention after 100 cycles). The present high‐performance P2‐KFMO microsphere cathode synthesized using earth‐abundant elements provides a new cost‐effective alternative to LIBs for large‐scale energy storage.     

Optimization of Von Mises Stress Distribution in Mesoporous α‐Fe2O3/C Hollow Bowls Synergistically Boosts Gravimetric/Volumetric Capacity and High‐Rate Stability in Alkali‐Ion Batteries

Hollow structures are often used to relieve the intrinsic strain on metal oxide electrodes in alkali‐ion batteries. Nevertheless, one common drawback is that the large interior space leads to low volumetric energy density and inferior electric conductivity. Here, the von Mises stress distribution on a mesoporous hollow bowl (HB) is simulated via the finite element method, and the vital role of the porous HB structure on strain‐relaxation behavior is confirmed. Then, N‐doped‐C coated mesoporous α‐Fe₂O₃ HBs are designed and synthesized using a multistep soft/hard‐templating strategy. The material has several advantages: (i) there is space to accommodate strains without sacrificing volumetric energy density, unlike with hollow spheres; (ii) the mesoporous hollow structure shortens ion diffusion lengths and allows for high‐rate induced lithiation reactivation; and (iii) the N‐doped carbon nanolayer can enhance conductivity. As an anode in lithium‐ion batteries, the material exhibits a very high reversible capacity of 1452 mAh g^?1 at 0.1 A g^?1, excellent cycling stability of 1600 cycles (964 mAh g^?1 at 2 A g^?1), and outstanding rate performance (609 mAh g^?1 at 8 A g^?1). Notably, the volumetric specific capacity of composite electrode is 42% greater than that of hollow spheres. When used in potassium‐ion batteries, the material also shows high capacity and cycle stability.     

MXene‐Bonded Flexible Hard Carbon Film as Anode for Stable Na/K‐Ion Storage

Hard carbon (HC) is a promising anode material for sodium‐ion batteries (SIBs) and potassium‐ion batteries (PIBs), but the volume change during the insertion/extraction of Na⁺ or K⁺ limits the cycle life, especially for PIBs due to the large ion size of K⁺. Moreover, the conventional anodes fabricated through the coating method cannot satisfy the requirement of flexible devices. Here, it is shown that 2D carbide flakes of Ti₃C₂T_x MXene can be used as multifunctional conductive binders for flexible HC electrodes. The use of MXene nanosheets eliminates the need for all the electrochemically inactive components in the conventional polyvinylidene fluoride–bonded HC electrode, including polymer binders, conductive additives, and current collectors. In MXene‐bonded HC electrodes, conductive and hydrophilic MXene 2D nanosheets construct a 3D network, which can effectively stabilize the electrode structure and accommodate the volume expansion of HC during the charge/discharge process, leading to an enhanced electrode capacity and excellent cycle performance as anodes for both SIBs and PIBs. Benefiting from the 3D conductive network, the MXene‐bonded HC film electrodes also present improved rate capability, indicating MXene is a very promising multifunctional binder for next‐generation flexible secondary rechargeable batteries.     

CoS Quantum Dot Nanoclusters for High‐Energy Potassium‐Ion Batteries

Potassium‐ion batteries (PIBs) are a promising alternative to lithium‐ion batteries because potassium is an abundant natural resource. To date, PIBs are in the early stages of exploration and only a few anode materials have been investigated. This study reports a cobalt sulfide and graphene (CoS@G) composite as anode electrode for PIBs for the first time. The composite features interconnect quantum dots of CoS nanoclusters uniformly anchored on graphene nanosheets. The coexistence of CoS quantum dot nanoclusters and graphene nanosheets endows the composite with large surface area, highly conductive network, robust structural stability, and excellent electrochemical energy storage performance. An unprecedented capacity of 310.8 mA h g^?1 at 500 mA g^?1 is obtained after 100 cycles, with a rate capability better than an equivalent sodium‐ion batteries (SIBs). This work provides the evidence that PIBs can be a promising alternative to SIBs, especially at high charge–discharge rates. The development of the CoS@G anode material also provides the basis of expanding the library of suitable anode materials for PIBs.     

Rambutan‐Like Hybrid Hollow Spheres of Carbon Confined Co3O4 Nanoparticles as Advanced Anode Materials for Sodium‐Ion Batteries

Transition metal oxides, possessing high theoretical specific capacities, are promising anode materials for sodium‐ion batteries. However, the sluggish sodiation/desodiation kinetics and poor structural stability restrict their electrochemical performance. To achieve high and fast Na storage capability, in this work, rambutan‐like hybrid hollow spheres of carbon confined Co₃O₄ nanoparticles are synthesized by a facile one‐pot hydrothermal treatment with postannealing. The hierarchy hollow structure with ultrafine Co₃O₄ nanoparticles embedded in the continuous carbon matrix enables greatly enhanced structural stability and fast electrode kinetics. When tested in sodium‐ion batteries, the hollow structured composite electrode exhibits an outstandingly high reversible specific capacity of 712 mAh g^?1 at a current density of 0.1 A g^?1, and retains a capacity of 223 mAh g^?1 even at a large current density of 5 A g^?1. Besides the superior Na storage capability, good cycle performance is demonstrated for the composite electrode with 74.5% capacity retention after 500 cycles, suggesting promising application in advanced sodium‐ion batteries.     

3D Carbon Nanotube Network Bridged Hetero‐Structured Ni‐Fe‐S Nanocubes toward High‐Performance Lithium,Sodium, and Potassium Storage

Lithium‐ion, sodium‐ion, and potassium‐ion batteries have captured tremendous attention in power supplies for various electric vehicles and portable electronic devices. However, their practical applications are severely limited by factors such as poor rate capability, fast capacity decay, sluggish charge storage dynamics, and low reversibility. Herein, hetero‐structured bimetallic sulfide (NiS/FeS) encapsulated in N‐doped porous carbon cubes interconnected with CNTs (Ni‐Fe‐S‐CNT) are prepared through a convenient co‐precipitation and post‐heat treatment sulfurization technique of the corresponding Prussian‐blue analogue nanocage precursor. This special 3D hierarchical structure can offer a stable interconnect and conductive network and shorten the diffusion path of ions, thereby greatly enhancing the mobility efficiency of alkali (Li, Na, K) ions in electrode materials. The Ni‐Fe‐S‐CNT nanocomposite maintains a charge capacity of 1535 mAh g^?1 at 0.2 A g^?1 for lithium ion batteries, 431 mAh g^?1 at 0.1 A g^?1 for sodium ion batteries, and 181 mAh g^?1 at 0.1 A g^?1 for potassium‐ion batteries, respectively. The high performance is mainly attributed to the 3D hierarchically high‐conductivity network architecture, in which the hetero‐structured FeS/NiS nanocubes provide fast Li⁺/Na⁺/K⁺ insertion/extraction and reduced ion diffusion paths, and the distinctive 3D networks maintain the electrical contact and guarantee the structural integrity.     

Freestanding Metallic 1T MoS2 with Dual Ion Diffusion Paths as High Rate Anode for Sodium‐Ion Batteries

This work studies for the first time the metallic 1T MoS₂ sandwich grown on graphene tube as a freestanding intercalation anode for promising sodium‐ion batteries (SIBs). Sodium is earth‐abundant and readily accessible. Compared to lithium, the main challenge of sodium‐ion batteries is its sluggish ion diffusion kinetic. The freestanding, porous, hollow structure of the electrode allows maximum electrolyte accessibility to benefit the transportation of Na⁺ ions. Meanwhile, the metallic MoS₂ provides excellent electron conductivity. The obtained 1T MoS₂ electrode exhibits excellent electrochemical performance: a high reversible capacity of 313 mAh g^?1 at a current density of 0.05 A g^?1 after 200 cycles and a high rate capability of 175 mAh g^?1 at 2 A g^?1. The underlying mechanism of high rate performance of 1T MoS₂ for SIBs is the high electrical conductivity and excellent ion accessibility. This study sheds light on using the 1T MoS₂ as a novel anode for SIBs.     

Controlled Design of Well‐Dispersed Ultrathin MoS2 Nanosheets inside Hollow Carbon Skeleton: Toward Fast Potassium Storage by Constructing Spacious “Houses” for K Ions

The large volume expansion induced by K⁺ intercalation is always a big challenge for designing high‐performance electrode materials in potassium‐ion storage system. Based on the idea that large‐sized ions should accommodate big “houses,” a facile‐induced growth strategy is proposed to achieve the self‐loading of MoS₂ clusters inside a hollow tubular carbon skeleton (HTCS). Meantime, a step‐by‐step intercalation technology is employed to tune the interlayer distance and the layer number of MoS₂. Based on the above, the ED‐MoS₂@CT hybrids are achieved by self‐loading and anchoring the well‐dispersed ultrathin MoS₂ nanosheets on the inner surface of HTCSs. This unique compositing model not only alleviates the mechanical strain efficiently, but also provides spacious “roads” (hollow tubular carbon skeleton) and “houses” (interlayer expanded ultrathin MoS₂ sheets) for fast K⁺ transition and storage. As an anode of potassium‐ion batteries, the resultant ED‐MoS₂@CT electrode delivers a high specific capacity of 148.5 mAh g^?1 at 2 A g^?1 after 10 000 cycles with only 0.002% fading per cycle. The assembled ED‐MoS₂@CT//PC potassium‐ion hybrid supercapacitor device shows a high energy density of 148 Wh kg^?1 at a power density of 965 W kg^?1, which is comparable to that of lithium‐ion hybrid supercapacitors.     

Designing and Understanding the Superior Potassium Storage Performance of Nitrogen/Phosphorus Co-Doped Hollow Porous Bowl-Like Carbon Anodes

Potassium-ion batteries (PIBs) are promising alternatives to lithium-ion batteries because of the advantage of abundant, low-cost potassium resources. However, PIBs are facing a pivotal challenge to develop suitable electrode materials for efficient insertion/extraction of large-radius potassium ions (K⁺). Here, a viable anode material composed of uniform, hollow porous bowl-like hard carbon dual doped with nitrogen (N) and phosphorus (P) (denoted as N/P-HPCB) is developed for high-performance PIBs. With prominent merits in structure, the as-fabricated N/P-HPCB electrode manifests extraordinary potassium storage performance in terms of high reversible capacity (458.3 mAh g⁻¹ after 100 cycles at 0.1 A g⁻¹), superior rate performance (213.6 mAh g⁻¹ at 4 A g⁻¹), and long-term cyclability (205.2 mAh g⁻¹ after 1000 cycles at 2 A g⁻¹). Density-functional theory calculations reveal the merits of N/P dual doping in favor of facilitating the adsorption/diffusion of K⁺ and enhancing the electronic conductivity, guaranteeing improved capacity, and rate capability. Moreover, in situ transmission electron microscopy in conjunction with ex situ microscopy and Raman spectroscopy confirms the exceptional cycling stability originating from the excellent phase reversibility and robust structure integrity of N/P-HPCB electrode during cycling. Overall, the findings shed light on the development of high-performance, durable carbon anodes for advanced PIBs.     

Optimizing Kinetics for Enhanced Potassium-Ion Storage in Carbon-Based Anodes

The sluggish kinetics in traditional graphite anode greatly limits its fast-charging capability, which is critically important for commercialization of potassium ion batteries (PIBs). Hard carbon possesses randomly oriented pseudo-graphitic crystallites, enabling homogeneous reaction current and superior rate performance. Herein, a series of hybrid anodes with different hard carbon/graphite ratios are prepared by uniformly mixing graphite and hard carbon with ball-milling. Comprehensive experimental results in combination phase-field simulations reveal that the hybrid anode possesses a homogeneous reaction current and an intriguing potential difference between K⁺-adsorbed hard carbon and non-potassiated graphite. The homogeneous reaction current in the hybrid anode promotes sufficient utilization of electrode material, leading to an increase in the reversible capacity. The present potential difference between K⁺-adsorbed hard carbon and non-potassiated graphite provides an additional electric field force that facilitates the diffusion of K⁺ from hard carbon into the nearest neighbor graphite. All these together, emphasize the synergistic effects between hard carbon and graphite in hybrid anodes toward satisfactory rate and cycling performance. The hybrid strategy proposed here is compatible with the commercial battery manufacturing, offering a practical pathway for the development of high-performance PIBs.     

Oxygen/Fluorine Dual‐Doped Porous Carbon Nanopolyhedra Enabled Ultrafast and Highly Stable Potassium Storage

Carbon‐based materials are promising anodes for potassium‐ion batteries (PIBs). However, due to the significant volume expansion and structural instability, it is still a challenge to achieve a high capacity, high rate and long cycle life for carbonaceous anodes. Herein, oxygen/fluorine dual‐doped porous carbon nanopolyhedra (OFPCN) is reported for the first time as a novel anode for PIBs, which exhibits a high reversible capacity of 481 mA h g^?1 at 0.05 A g^?1 and excellent performance of 218 mA h g^?1 after 2000 cycles at 1 A g^?1 with 92% capacity retention. Even after 5000 robust cycles at 10 A g^?1 with charging/discharging time of around 40 s, an unprecedented capacity of 111 mA h g^?1 is still maintained. Such ultrafast potassium storage and unprecedented cycling stability have been seldom reported in PIBs. Quantitative kinetics analysis reveals that both diffusion and capacitance processes are involved in the potassium storage mechanism. Density functional theory calculations demonstrate that the O/F dual‐doped porous carbon promotes the K‐adsorption ability and can absorb multiple K atoms with slight structural distortion, which accounts for the high specific capacity, outstanding rate capability, and excellent cycling stability of the OFPCN anode.     

Novel Insoluble Organic Cathodes for Advanced Organic K‐Ion Batteries

Organic redox‐active molecules are inborn electrodes to store large‐radius potassium (K) ion. High‐performance organic cathodes are important for practical usage of organic potassium‐ion batteries (OPIBs). However, small‐molecule organic cathodes face serious dissolution problems against liquid electrolytes. A novel insoluble small‐molecule organic cathode [N,N′‐bis(2‐anthraquinone)]‐perylene‐3,4,9,10‐tetracarboxydiimide (PTCDI‐DAQ, 200 mAh g^?1) is initially designed for OPIBs. In half cells (1–3.8 V vs K⁺/K) using 1 m KPF₆ in dimethoxyethane (DME), PTCDI‐DAQ delivers a highly stable specific capacity of 216 mAh g^?1 and still holds the value of 133 mAh g^?1 at an ultrahigh current density of 20 A g^?1 (100 C). Using reduced potassium terephthalate (K₄TP) as the organic anode, the resulting K₄TP||PTCDI‐DAQ OPIBs with the electrolyte 1 m KPF₆ in DME realize a high energy density of maximum 295 Wh kg^?1_cathode (213 mAh g^?1_cathode × 1.38 V) and power density of 13 800 W Kg^?1_cathode (94 mAh g^?1 × 1.38 V @ 10 A g^?1) during the working voltage of 0.2–3.2 V. Meanwhile, K₄TP||PTCDI‐DAQ OPIBs fulfill the superlong lifespan with a stable discharge capacity of 62 mAh g^?1_cathode after 10 000 cycles and 40 mAh g^?1_cathode after 30 000 cycles (3 A g^?1). The integrated performance of PTCDI‐DAQ can currently defeat any cathode reported in K‐ion half/full cells.     

A New rGO‐Overcoated Sb2Se3 Nanorods Anode for Na+ Battery: In Situ X‐Ray Diffraction Study on a Live Sodiation/Desodiation Process

Sodium ion batteries (SIBs) are a promising alternative to lithium ion batteries for a broader range of energy storage applications in the future. However, the development of high‐performance anode materials is a bottleneck of SIBs advancement. In this work, Sb₂Se₃ nanorods uniformly wrapped by reduced graphene oxide (rGO) as a promising anode material for SIBs are reported. The results show that such Sb₂Se₃/rGO hybrid anode yields a high reversible mass‐specific energy capacity of 682, 448, and 386 mAh g^?1 at a rate of 0.1, 1.0, and 2.0 A g^?1, respectively, and sustains at least 500 stable cycles at a rate of 1.0 A g^?1 with an average mass‐specific energy capacity of 417 mAh g^?1 and capacity retention of 90.2%. In situ X‐ray diffraction study on a live SIB cell reveals that the observed high performance is a result of the combined Na⁺ intercalation, conversion reaction between Na⁺ and Se, and alloying reaction between Na⁺ and Sb. The presence of rGO also plays a key role in achieving high rate capacity and cycle stability by providing good electrical conductivity, tolerant accommodation to volume change, and strong electron interactions to the base Sb₂Se₃ anode.     

Walnut‐Like Multicore–Shell MnO Encapsulated Nitrogen‐Rich Carbon Nanocapsules as Anode Material for Long‐Cycling and Soft‐Packed Lithium‐Ion Batteries

Metal oxide‐based nanomaterials are widely studied because of their high‐energy densities as anode materials in lithium‐ion batteries. However, the fast capacity degradation resulting from the large volume expansion upon lithiation hinders their practical application. In this work, the preparation of walnut‐like multicore–shell MnO encapsulated nitrogen‐rich carbon nanocapsules (MnO@NC) is reported via a facile and eco‐friendly process for long‐cycling Li‐ion batteries. In this hybrid structure, MnO nanoparticles are uniformly dispersed inside carbon nanoshells, which can simultaneously act as a conductive framework and also a protective buffer layer to restrain the volume variation. The MnO@NC nanocapsules show remarkable electrochemical performances for lithium‐ion batteries, exhibiting high reversible capability (762 mAh g^?1 at 100 mA g^?1) and stable cycling life (624 mAh g^?1 after 1000 cycles at 1000 mA g^?1). In addition, the soft‐packed full batteries based on MnO@NC nanocapsules anodes and commercial LiFePO₄ cathodes present good flexibility and cycling stability.     

Facile Spraying Synthesis and High‐Performance Sodium Storage of Mesoporous MoS2/C Microspheres

A facile one‐step spraying synthesis of MoS₂/C microspheres and their enhanced electrochemical performance as anode of sodium‐ion batteries is reported. An aerosol spraying pyrolysis without any template is employed to synthesize MoS₂/C microspheres, in which ultrathin MoS₂ nanosheets (≈2 nm) with enlarged interlayers (≈0.64 nm) are homogeneously embedded in mesoporous carbon microspheres. The as‐synthesized mesoporous MoS₂/C microspheres with 31 wt% carbon have been applied as an anode material for sodium ion batteries, demonstrating long cycling stability (390 mAh g^?1 after 2500 cycles at 1.0 A g^?1) and high rate capability (312 mAh g^?1 at 10.0 A g^?1 and 244 mAh g^?1 at 20.0 A g^?1). The superior electrochemical performance is due to the uniform distribution of ultrathin MoS₂ nanosheets in mesoporous carbon frameworks. This kind of structure not only effectively improves the electronic and ionic transport through MoS₂/C microspheres, but also minimizes the influence of pulverization and aggregation of MoS₂ nanosheets during repeated sodiation and desodiation.     

High Reversible Pseudocapacity in Mesoporous Yolk–Shell Anatase TiO2/TiO2(B) Microspheres Used as Anodes for Li‐Ion Batteries

As an anode material for lithium‐ion batteries, titanium dioxide (TiO₂) shows good gravimetric performance (336 mAh g^?1 for LiTiO₂) and excellent cyclability. To address the poor rate behavior, slow lithium‐ion (Li⁺) diffusion, and high irreversible capacity decay, TiO₂ nanomaterials with tuned phase compositions and morphologies are being investigated. Here, a promising material is prepared that comprises a mesoporous “yolk–shell” spherical morphology in which the core is anatase TiO₂ and the shell is TiO₂(B). The preparation employs a NaCl‐assisted solvothermal process and the electrochemical results indicate that the mesoporous yolk–shell microspheres have high specific reversible capacity at moderate current (330.0 mAh g^?1 at C/5), excellent rate performance (181.8 mAh g^?1 at 40C), and impressive cyclability (98% capacity retention after 500 cycles). The superior properties are attributed to the TiO₂(B) nanosheet shell, which provides additional active area to stabilize the pseudocapacity. In addition, the open mesoporous morphology improves diffusion of electrolyte throughout the electrode, thereby contributing directly to greatly improved rate capacity.     

A Stable Conversion and Alloying Anode for Potassium‐Ion Batteries: A Combined Strategy of Encapsulation and Confinement

Potassium‐ion batteries based on conversion/alloying reactions have high potential applications in new‐generation large‐scale energy storage. However, their applications are hindered by inherent large‐volume variations and sluggish kinetics of the conversion/alloying‐type electrode materials during the repeated insertion and extraction of bulky K⁺ ions. Although some efforts have been focused on this issue, the reported potassium‐ion batteries still suffer from poor cycling lifespans. Here, a superior stable antimony selenide (Sb₂Se₃) anode is reported for high‐performance potassium‐ion batteries through a combined strategy of conductive encapsulation and 2D confinement. The Sb₂Se₃ nanorods are uniformly coated with a conductive N‐doped carbon layer and then confined between graphene nanosheets. The synergistic effects between conductive coating and confinement effectively buffer the large volumetric variation of the conversion/alloying anodes, which can maintain structural stability for superior cyclability. The as‐prepared anodes exhibit a high reversible specific capacity of ≈590 mA h g^?1 and outstanding cycling stability over 350 cycles. In situ and ex situ characterizations reveal a high structural integration of the large‐volume‐change Sb₂Se₃ anodes during a reversible K storage mechanism of two‐step conversion and multistep alloying processes. This work can open up a new possibility for the design of stable conversion/alloying‐based anodes for high‐performance potassium‐ion batteries.     

Multicore–Shell Bi@N‐doped Carbon Nanospheres for High Power Density and Long Cycle Life Sodium‐ and Potassium‐Ion Anodes

Bismuth (Bi) is an attractive material as anodes for both sodium‐ion batteries (NIBs) and potassium‐ion batteries (KIBs), because it has a high theoretical gravimetric capacity (386 mAh g^?1) and high volumetric capacity (3800 mAh L^?1). The main challenges associated with Bi anodes are structural degradation and instability of the solid electrolyte interphase (SEI) resulting from the huge volume change during charge/discharge. Here, a multicore–shell structured Bi@N‐doped carbon (Bi@N‐C) anode is designed that addresses these issues. The nanosized Bi spheres are encapsulated by a conductive porous N‐doped carbon shell that not only prevents the volume expansion during charge/discharge but also constructs a stable SEI during cycling. The Bi@N‐C exhibits unprecedented rate capability and long cycle life for both NIBs (235 mAh g^?1 after 2000 cycles at 10 A g^?1) and KIBs (152 mAh g^?1 at 100 A g^?1). The kinetic analysis reveals the outstanding electrochemical performance can be attributed to significant pseudocapacitance behavior upon cycling.     

Pseudocapacitive Trimetal Fe0.8CoMnO4 Nanoparticles@Carbon Nanofibers as High‐Performance Sodium Storage Anode with Self‐Supported Mechanism

Trimetal Fe_0.8CoMnO₄ (FCMO) nanocrystals with a diameter of about 50 nm perfectly embedded in N doped‐carbon composite nanofibers (denoted as FCMO@C) are successfully prepared through integrating double‐nozzle electrospinning with a drying and calcination process. The as‐prepared FCMO@C nanofibers maintain a high reversible capacity of 420 mAh g^?1 and about 90% capacity retention after 200 cycles at 0.1 A g^?1. For a long‐term cycle, the FCMO@C electrode exhibits excellent cycling stability (87% high capacity retention at 1 A g^?1 after 950 cycles). Kinetic analysis demonstrates that the electrochemical characteristics of the FCMO@C corresponds to the pseudocapacitive approach in charge storage as an anode for sodium ion batteries, which dominantly attributes the credit to FCMO nanocrystals to shorten the migration distance of Na⁺ ions and the nitrogen‐doped carbon skeleton to enhance the electronic transmission and favorably depress the volume expansion during the repeated insertion/extraction of Na⁺ ions. More significantly, a self‐supported mechanism via continuous electrochemical redox reaction of Fe, Co, and Mn can effectively relieve the volume change during charge and discharge. Therefore, this work can provide a new avenue to improve the sodium storage performance of the oxide anode materials.