3D Hierarchical Porous α‐Fe2O3 Nanosheets for High‐Performance Lithium‐Ion Batteries

To develop a long cycle life and good rate capability electrode, 3D hierarchical porous α‐Fe₂O₃ nanosheets are fabricated on copper foil and directly used as binder‐free anode for lithium‐ion batteries. This electrode exhibits a high reversible capacity and excellent rate capability. A reversible capacity up to 877.7 mAh g^?1 is maintained at 2 C (2.01 A g^?1) after 1000 cycles, and even when the current is increased to 20 C (20.1 A g^?1), a capacity of 433 mA h g^?1 is retained. The unique porous 3D hierarchical nanostructure improves electronic–ionic transport, mitigates the internal mechanical stress induced by the volume variations of the electrode upon cycling, and forms a 3D conductive network during cycling. No addition of any electrochemically inactive conductive agents or polymer binders is required. Therefore, binder‐free electrodes further avoid the uneven distribution of conductive carbon on the current collector due to physical mixing and the addition of an insulator (binder), which has benefits leading to outstanding electrochemical performance.     

Biomimetic Spider‐Web‐Like Composites for Enhanced Rate Capability and Cycle Life of Lithium Ion Battery Anodes

It is crucial to control the structure and composition of composite anode materials to enhance the cell performance of such anode materials for lithium ion batteries. Herein, a biomimetic strategy is demonstrated for the design of high performance anode materials, inspired by the structural characteristics and working principles of sticky spider‐webs. Hierarchically porous, sticky, spider‐web‐like multiwall carbon nanotube (MWCNT) networks are prepared through a process involving ozonation, ice‐templating assembly, and thermal treatment, thereby integrating the networks with γ‐Fe₂O₃ particles. The spider‐web‐like MWCNT/γ‐Fe₂O₃ composite network not only traps the active γ‐Fe₂O₃ materials tightly but also provides fast charge transport through the 3D internetworked pathways and the mechanical integrity. Consequently, the composite web shows a high capacity of ≈822 mA h g^?1 at 0.05 A g^?1, fast rate capability with ≈72.3% retention at rates from 0.05 to 1 A g^?1, and excellent cycling stability of >88% capacity retention after 310 cycles with a Coulombic efficiency >99%. These remarkable electrochemical performances are attributed to the complementarity of the 3D spider‐web‐like structure with the strong attachment of γ‐Fe₂O₃ particles on the sticky surface. This synthetic strategy offers an environmentally safe, simple, and cost‐effective avenue for the biomimetic design of high performance energy storage materials.     

Hollow NiCo2S4 Nanospheres Hybridized with 3D Hierarchical Porous rGO/Fe2O3 Composites toward High‐Performance Energy Storage Device

Hierarchical hollow NiCo₂S₄ microspheres with a tunable interior architecture are synthesized by a facile and cost‐effective hydrothermal method, and used as a cathode material. A three‐dimensional (3D) porous reduced graphene oxide/Fe₂O₃ composite (rGO/Fe₂O₃) with precisely controlled particle size and morphology is successfully prepared through a scalable facile approach, with well‐dispersed Fe₂O₃ nanoparticles decorating the surface of rGO sheets. The fixed Fe₂O₃ nanoparticles in graphene efficiently prevent the intermediates during the redox reaction from dissolving into the electrolyte, resulting in long cycle life. KOH activation of the rGO/Fe₂O₃ composite is conducted for the preparation of an activated carbon material–based hybrid to transform into a 3D porous carbon material–based hybrid. An energy storage device consisting of hollow NiCo₂S₄ microspheres as the positive electrode, the 3D porous rGO/Fe₂O₃ composite as the negative electrode, and KOH solution as the electrolyte with a maximum energy density of 61.7 W h kg^?1 is achieved owing to its wide operating voltage range of 0–1.75 V and the designed 3D structure. Moreover, the device exhibits a high power density of 22 kW kg^?1 and a long cycle life with 90% retention after 1000 cycles at the current density of 1 A g^?1.     

Deactivating Defects in Graphenes with Al2O3 Nanoclusters to Produce Long‐Life and High‐Rate Sodium‐Ion Batteries

Carbon materials are the most promising anodes for sodium‐ion batteries (SIBs), but low initial Coulombic efficiency (ICE) and poor cyclic stability hinder their practical use. It is shown herein, that an effective but simple remedy for these problems can be achieved by deactivating defects in the carbon with Al₂O₃ nanocluster coverage. A 3D porous graphene monolith (PGM) is used as the model material and Al₂O₃ nanoclusters around 1 nm are grown on the defects of graphene. It is shown that these Al₂O₃ nanoclusters suppress the decomposition of conductive sodium salt in the electrolyte, resulting in the formation of a thin and homogenous solid electrolyte interphase (SEI). In addition, Al₂O₃ nanoclusters appear to reduce the detrimental etching of the SEI by hydrogen fluoride (HF) and improve its stability. Therefore, after the introduction of Al₂O₃ nanoclusters, the ICE, cyclic stability, and rate capability of the PGM are greatly improved. A higher ICE (70.2%) and capacity retention (82.9% after 500 cycles at 0.5 A g^?1) than those of normally reported for large surface area carbons are achieved. This work indicates a new way to deactivate defects and modify the SEI of carbon materials, and hopefully accelerate the commercialization of carbon materials as anode materials for SIBs.     

Identification of Phase Control of Carbon‐Confined Nb2O5 Nanoparticles toward High‐Performance Lithium Storage

Niobium pentoxides (Nb₂O₅) have attracted extensive interest for ultrafast lithium‐ion batteries due to their impressive rate/capacity performance and high safety as intercalation anodes. However, the intrinsic insulating properties and unrevealed mechanisms of complex phases limit their further applications. Here, a facile and efficient method is developed to construct three typical carbon‐confined Nb₂O₅ (TT‐Nb₂O₅@C, T‐Nb₂O₅@C, and H‐Nb₂O₅@C) nanoparticles via a mismatched coordination reaction during the solvothermal process and subsequent controlled heat treatment, and different phase effects are investigated on their lithium storage properties on the basis of both experimental and computational approaches. The thin carbon coating and nanoscale size can endow Nb₂O₅ with a high surface area, high conductivity, and short diffusion length. As a proof‐of‐concept application, when employed as LIB anode materials, the resulting T‐Nb₂O₅@C nanoparticles display higher rate capability and better cycling stability as compared with TT‐Nb₂O₅@C and H‐Nb₂O₅@C nanoparticles. Furthermore, a synergistic effect is investigated and demonstrated between fast diffusion pathways and stable hosts in T‐Nb₂O₅ for ultrafast and stable lithium storage, based on crystal structure analysis, in situ X‐ray diffraction analysis, and density functional theoretical calculations. Therefore, the proposed synthetic strategy and obtained deep insights will stimulate the development of Nb₂O₅ for ultrafast and long‐life LIBs.     

A Ternary Fe1−xS@Porous Carbon Nanowires/Reduced Graphene Oxide Hybrid Film Electrode with Superior Volumetric and Gravimetric Capacities for Flexible Sodium Ion Batteries

Smart construction of ultraflexible electrodes with superior gravimetric and volumetric capacities is still challenging yet significant for sodium ion batteries (SIBs) toward wearable electronic devices. Herein, a hybrid film made of hierarchical Fe_1?xS‐filled porous carbon nanowires/reduced graphene oxide (Fe_1?xS@PCNWs/rGO) is synthesized through a facile assembly and sulfuration strategy. The resultant hybrid paper exhibits high flexibility and structural stability. The multidimensional paper architecture possesses several advantages, including rendering an efficient electron/ion transport network, buffering the volume expansion of Fe_1?xS nanoparticles, mitigating the dissolution of polysulfides, and enabling superior kinetics toward efficient sodium storage. When evaluated as a self‐supporting anode for SIBs, the Fe_1?xS@PCNWs/rGO paper electrode exhibits remarkable reversible capacities of 573–89 mAh g^?1 over 100 consecutive cycles at 0.1 A g^?1 with areal mass loadings of 0.9–11.2 mg cm^?2 and high volumetric capacities of 424–180 mAh cm^?3 in the current density range of 0.2–5 A g^?1. More competitively, a SIB based on this flexible Fe_1?xS@PCNWs/rGO anode demonstrates outstanding electrochemical properties, thus highlighting its enormous potential in versatile flexible and wearable applications.     

Iron‐Oxide‐Based Advanced Anode Materials for Lithium‐Ion Batteries

Iron oxides, such as Fe₂O₃ and Fe₃O₄, have recently received increased attention as very promising anode materials for rechargeable lithium‐ion batteries (LIBs) because of their high theoretical capacity, non‐toxicity, low cost, and improved safety. Nanostructure engineering has been demonstrated as an effective approach to improve the electrochemical performance of electrode materials. Here, recent research progress in the rational design and synthesis of diverse iron oxide‐based nanomaterials and their lithium storage performance for LIBs, including 1D nanowires/rods, 2D nanosheets/flakes, 3D porous/hierarchical architectures, various hollow structures, and hybrid nanostructures of iron oxides and carbon (including amorphous carbon, carbon nanotubes, and graphene). By focusing on synthesis strategies for various iron‐oxide‐based nanostructures and the impacts of nanostructuring on their electrochemical performance, novel approaches to the construction of iron‐oxide‐based nanostructures are highlighted and the importance of proper structural and compositional engineering that leads to improved physical/chemical properties of iron oxides for efficient electrochemical energy storage is stressed. Iron‐oxide‐based nanomaterials stand a good chance as negative electrodes for next generation LIBs.     

3D Amorphous Carbon with Controlled Porous and Disordered Structures as a High‐Rate Anode Material for Sodium‐Ion Batteries

Sodium‐ion batteries (SIBs) have a promising application prospect for energy storage systems due to the abundant resource. Amorphous carbon with high electronic conductivity and high surface area is likely to be the most promising anode material for SIBs. However, the rate capability of amorphous carbon in SIBs is still a big challenge because of the sluggish kinetics of Na⁺ ions. Herein, a three‐dimensional amorphous carbon (3DAC) with controlled porous and disordered structures is synthesized via a facile NaCl template‐assisted method. Combination of open porous structures of 3DAC, the increased disordered structures can not only facilitate the diffusion of Na⁺ ions but also enhance the reversible capacity of Na storage. When applied as anode materials for SIBs, 3DAC exhibits excellent rate capability (66 mA h g^?1 at 9.6 A g^?1) and high reversible capacity (280 mA h g^?1 at a low current density of 0.03 A g^?1). Moreover, the controlled porous structures by the NaCl template method provide an appropriate specific surface area, which contributes to a relatively high initial Coulombic efficiency of 75%. Additionally, the high‐rate 3DAC material is prepared via a green approach originating from low‐cost pitch and NaCl template, demonstrating an appealing development of carbon anode materials for SIBs.     

Ultrafine MoO2‐Carbon Microstructures Enable Ultralong‐Life Power‐Type Sodium Ion Storage by Enhanced Pseudocapacitance

The achievement of the superior rate capability and cycling stability is always the pursuit of sodium‐ion batteries (SIBs). However, it is mainly restricted by the sluggish reaction kinetics and large volume change of SIBs during the discharge/charge process. This study reports a facile and scalable strategy to fabricate hierarchical architectures where TiO₂ nanotube clusters are coated with the composites of ultrafine MoO₂ nanoparticles embedded in carbon matrix (TiO₂@MoO₂‐C), and demonstrates the superior electrochemical performance as the anode material for SIBs. The ultrafine MoO₂ nanoparticles and the unique nanorod structure of TiO₂@MoO₂‐C help to decrease the Na⁺ diffusion length and to accommodate the accompanying volume expansion. The good integration of MoO₂ nanoparticles into carbon matrix and the cable core role of TiO₂ nanotube clusters enable the rapid electron transfer during discharge/charge process. Benefiting from these structure merits, the as‐made TiO₂@MoO₂‐C can deliver an excellent cycling stability up to 10 000 cycles even at a high current density of 10 A g^?1. Additionally, it exhibits superior rate capacities of 110 and 76 mA h g^?1 at high current densities of 10 and 20 A g^?1, respectively, which is mainly attributed to the high capacitance contribution.     

Application of a fluorescent biosensor based‐on magneto‐γ‐Fe2O3–methyldopa nanoparticles for adsorption of human serum albumin

Understanding and controlling the interaction between the polymer methyldopa (2‐amino‐3‐(3,4‐dihydroxyphenyl)‐2‐methyl‐propanoic acid) (PMDP)–γ‐Fe₂O₃ nanoparticles and biological fluids is important if the potential of nanoparticles (NPs) in biomedicine is to be realized. Physicochemical studies on the interactions between proteins and NPs are influenced by the surface properties of the NPs. To identify the effects of the NP surface, interactions between human serum albumin (HSA) and PMDP–γ‐Fe₂O₃ NPs were investigated. Here, the adsorption of HSA onto small (10–30 nm diameter) PMDP–γ‐Fe₂O₃ NPs was quantitatively analyzed using spectroscopic methods. The fluorescence quenching data were checked for the inner‐filter effect, the main confounding factor in the observed quenching. The binding constants, K_a, were calculated at different temperatures, using a nonlinear fit to the experimental data, and the thermodynamic parameters ?H, ?S and ?G were given. The obtained thermodynamic signature suggests that hydrophobic interactions at least are present. This result indicates that the structure of the protein turns from a structureless denatured state at pH 3 into an ordered biologically active native state on addition of PMDP–γ‐Fe₂O₃ NPs. Copyright © 2015 John Wiley & Sons, Ltd.     

Low‐Temperature Solution‐Based Phosphorization Reaction Route to Sn4P3/Reduced Graphene Oxide Nanohybrids as Anodes for Sodium Ion Batteries

Different from previously reported mechanical alloying route to synthesize Sn _x P₃, novel Sn₄P₃/reduced graphene oxide (RGO) hybrids are synthesized for the first time through an in situ low‐temperature solution‐based phosphorization reaction route from Sn/RGO. Sn₄P₃ nanoparticles combining with advantages of high conductivity of Sn and high capacity of P are homogenously loaded on the RGO nanosheets, interconnecting to form 3D mesoporous architecture nanostructures. The Sn₄P₃/RGO hybrid architecture materials exhibit significantly improved electrochemical performance of high reversible capacity, high‐rate capability, and excellent cycling performance as sodium ion batteries (SIBs) anode materials, showing an excellent reversible capacity of 656 mA h g^?1 at a current density of 100 mA g^?1 over 100 cycles, demonstrating a greatly enhanced rate capability of a reversible capacity of 391 mA h g^?1 even at a high current density of 2.0 A g^?1. Moreover, Sn₄P₃/RGO SIBs anodes exhibit a superior long cycling life, delivering a high capacity of 362 mA h g^?1 after 1500 cycles at a high current density of 1.0 A g^?1. The outstanding cycling performance and rate capability of these porous hierarchical Sn₄P₃/RGO hybrid anodes can be attributed to the advantage of porous structure, and the synergistic effect between Sn₄P₃ nanoparticles and RGO nanosheets.     

Amorphous Carbon Coated High Grain Boundary Density Dual Phase Li4Ti5O12‐TiO2: A Nanocomposite Anode Material for Li‐Ion Batteries

This work introduces an effective, inexpensive, and large‐scale production approach to the synthesis of a carbon coated, high grain boundary density, dual phase Li₄Ti₅O₁₂‐TiO₂ nanocomposite anode material for use in rechargeable lithium‐ion batteries. The microstructure and morphology of the Li₄Ti₅O₁₂‐TiO₂‐C product were characterized systematically. The Li₄Ti₅O₁₂‐TiO₂‐C nanocomposite electrode yielded good electrochemical performance in terms of high capacity (166 mAh g^?1 at a current density of 0.5 C), good cycling stability, and excellent rate capability (110 mAh g^?1 at a current density of 10 C up to 100 cycles). The likely contributing factors to the excellent electrochemical performance of the Li₄Ti₅O₁₂‐TiO₂‐C nanocomposite could be related to the improved morphology, including the presence of high grain boundary density among the nanoparticles, carbon layering on each nanocrystal, and grain boundary interface areas embedded in a carbon matrix, where electronic transport properties were tuned by interfacial design and by varying the spacing of interfaces down to the nanoscale regime, in which the grain boundary interface embedded carbon matrix can store electrolyte and allows more channels for the Li+ ion insertion/extraction reaction. This research suggests that carbon‐coated dual phase Li₄Ti₅O₁₂‐TiO₂ nanocomposites could be suitable for use as a high rate performance anode material for lithium‐ion batteries.     

Superior Lithium Storage Properties of β‐FeOOH

Several crystal forms of FeOOH are recently reported to be highly promising for lithium storage due to their high capacity, low cost, and environmental friendliness. In particular, β‐FeOOH has shown a capacity of ≈1000 mAh g^?1, which is comparable to other promising iron‐based anodes, such as Fe₂O₃ and Fe₃O_4. However, its storage mechanisms are unclear and the potential for further improvement remains unexplored. Here, it is shown that this material can have a very high reversible capacity of ≈1400 mAh g^?1, which is 20%–40% higher than Fe₂O₃ and Fe₃O₄. Such a high capacity is delivered from a series of reactions including intercalation and conversion reactions, formation/deformation of solid‐state electrolyte interface layers and interfacial storage. The mechanisms are studied by a combination of electrochemical and X‐ray absorption near edge spectroscopic approaches. Moreover, very long cycling performance, that is, after even more than 3000 cycles the material still has a significant capacity of more than 800 mAh g^?1, is obtained by a simple electrode design involving introducing a rigid support into porous electrodes. Such long cycling performance is for the first time achieved for high‐capacity materials based on conversion reactions.     

Ice Templated Free‐Standing Hierarchically WS2/CNT‐rGO Aerogel for High‐Performance Rechargeable Lithium and Sodium Ion Batteries

A hybrid nanoarchitecture aerogel composed of WS₂ nanosheets and carbon nanotube‐reduced graphene oxide (CNT‐rGO) with ordered microchannel three‐dimensional (3D) scaffold structure was synthesized by a simple solvothermal method followed by freeze‐drying and post annealing process. The 3D ordered microchannel structures not only provide good electronic transportation routes, but also provide excellent ionic conductive channels, leading to an enhanced electrochemical performance as anode materials both for lithium‐ion batteries (LIBs) and sodium‐ion batteries (SIBs). Significantly, WS₂/CNT‐rGO aerogel nanostructure can deliver a specific capacity of 749 mA h g^?1 at 100 mA g^?1 and a high first‐cycle coulombic efficiency of 53.4% as the anode material of LIBs. In addition, it also can deliver a capacity of 311.4 mA h g^?1 at 100 mA g^?1, and retain a capacity of 252.9 mA h g^?1 at 200 mA g^?1 after 100 cycles as the anode electrode of SIBs. The excellent electrochemical performance is attributed to the synergistic effect between the WS₂ nanosheets and CNT‐rGO scaffold network and rational design of 3D ordered structure. These results demonstrate the potential applications of ordered CNT‐rGO aerogel platform to support transition‐metal‐dichalcogenides (i.e., WS₂) for energy storage devices and open up a route for material design for future generation energy storage devices.     

A High‐Power Na3V2(PO4)3‐Bi Sodium‐Ion Full Battery in a Wide Temperature Range

Sodium‐ion batteries (SIBs) that operate in a wide temperature range are in high demand for practical large‐scale electric energy storage. Herein, a novel full SIB is composed of a bulk Bi anode, a Na₃V₂(PO₄)₃/carbon nanotubes composite (NVP‐CNTs) cathode and a NaPF₆‐diglyme electrolyte. The Bi anode gradually evolves into a porous network in the ether‐based electrolyte during initial cycles, and in the NVP‐CNTs cathode the NVP is cross linked by CNTs to show large exchange current density. These unique features merit the full SIB of Bi//NVP‐CNTs with high Na⁺ diffusion coefficient and low reaction activation energy, and hence fast Na⁺ transport and facile redox reaction kinetics. The resultant full SIB presents high power density of 2354.6 W kg^?1 and energy density of 150 Wh kg^?1 and superior cycling stability in a wide temperature range from ?15 to 45 °C. This will shed light on battery design, and promote their development for practical applications in various weather conditions.     

Mn‐Rich P′2‐Na0.67[Ni0.1Fe0.1Mn0.8]O2 as High‐Energy‐Density and Long‐Life Cathode Material for Sodium‐Ion Batteries

Herein, P′2‐type Na_0.67[Ni_0.1Fe_0.1Mn_0.8]O₂ is introduced as a promising new cathode material for sodium‐ion batteries (SIBs) that exhibits remarkable structural stability during repetitive Na⁺ de/intercalation. The O? Ni? O? Mn? O? Fe? O bond in the octahedra of transition‐metal layers is used to suppress the elongation of the Mn? O bond and to improve the electrochemical activity, leading to the highly reversible Na storage mechanism. A high discharge capacity of ≈220 mAh g^?1 (≈605 Wh kg^?1) is delivered at 0.05 C (13 mAg^?1) with a high reversible capacity of ≈140 mAh g^?1 at 3 C and excellent capacity retention of 80% over 200 cycles. This performance is associated with the reversible P′2–OP4 phase transition and small volume change upon charge and discharge (≈3%). The nature of the sodium storage mechanism in a full cell paired with a hard carbon anode reveals an unexpectedly high energy density of ≈542 Wh kg^?1 at 0.2 C and good capacity retention of ≈81% for 500 cycles at 1 C (260 mAg^?1).     

Reliable and General Route to Inverse Opal Structured Nanohybrids of Carbon‐Confined Transition Metal Sulfides Quantum Dots for High‐Performance Sodium Storage

Sodium‐ion batteries (SIBs) have recently attracted increasing attention as the promising alternative to lithium‐ion batteries due to their multiple advantages of abundant reserves and low cost. However, the development of highly desirable anode materials suitable for SIBs is still hampered by a rather low capacity, poor rate capability, and cycling stability. Herein, a deliberate design to implement reliable and simple fabrication of an inverse opal structured nanohybrid of carbon‐confined various transition metal sulfides quantum dots (QDs) is presented. Comprehensive characterizations demonstrate that the hybrids hold a 3D architecture with uniform dispersion of QDs in a conductive carbon matrix that in turn encapsulates these quantum dots. With Co₉S₈ as an example, such a unique architecture, when applied as the anode of SIBs, endows the hybrids with multiple advantages including a high reversible specific capacity, extraordinary high rate capability, and excellent durability over 2000 cycles charging–discharging process.     

Confined Fe2VO4⊂Nitrogen‐Doped Carbon Nanowires with Internal Void Space for High‐Rate and Ultrastable Potassium‐Ion Storage

Developing low‐cost, high‐capacity, high‐rate, and robust earth‐abundant electrode materials for energy storage is critical for the practical and scalable application of advanced battery technologies. Herein, the first example of synthesizing 1D peapod‐like bimetallic Fe₂VO₄ nanorods confined in N‐doped carbon porous nanowires with internal void space (Fe₂VO₄?NC nanopeapods) as a high‐capacity and stable anode material for potassium‐ion batteries (KIBs) is reported. The peapod‐like Fe₂VO₄?NC nanopeapod heterostructures with interior void space and external carbon shell efficiently prevent the aggregation of the active materials, facilitate fast transportation of electrons and ions, and accommodate volume variation during the cycling process, which substantially boosts the rate and cycling performance of Fe₂VO₄. The Fe₂VO₄?NC electrode exhibits high reversible specific depotassiation capacity of 380 mAh g^?1 at 100 mA g^?1 after 60 cycles and remarkable rate capability as well as long cycling stability with a high capacity of 196 mAh g^?1 at 4 A g^?1 after 2300 cycles. The first‐principles calculations reveal that Fe₂VO₄?NC nanopeapods have high ionic/electronic conductivity characteristics and low diffusion barriers for K⁺‐intercalation. This study opens up new way for investigating high‐capacity metal oxide as high‐rate and robust electrode materials for KIBs.     

New Binder‐Free Metal Phosphide–Carbon Felt Composite Anodes for Sodium‐Ion Battery

Metal phosphides are promising anode candidates for sodium‐ion batteries (SIBs) due to their high specific capacity and low operating potential but suffer from poor cycling stability caused by huge volume expansion and poor solid‐state ion transfer rate. Herein, a new strategy to grow a new class of mesoporous metal phosphide nanoarrays on carbon felt (CF) as binder‐free anodes for SIBs is reported. The resultant integrated electrodes demonstrate excellent cycling life up to 1000 times (>90% retention rate) and high rate capability of 535 mAh g^?1 at a current density of 4 A g^?1. Detailed characterization reveals that the synergistic effect of unique mesoporous structure for accommodating huge volume expansion during sodiation/desodiation process, ultrasmall primary particle size (≈10 nm) for providing larger electrode/electrolyte contact area and shorter ion diffusion distance, and 3D conductive networks for facilitating the electrochemical reaction, leads to the extraordinary battery performance. Remarkably, a full SIB using the new CoP₄/CF anode and a Na₃V₂(PO₄)₂F₃ cathode delivers an average operating voltage of ≈3.0 V, a reversible capacity of 553 mAh g^?1, and very high energy density of ≈280 Wh kg^?1 for SIBs. A flexible SIB with outstanding mechanical strength based on this binder‐free new anode is also demonstrated.     

Rational Construction of Self‐Standing Sulfur‐Doped Fe2O3 Anodes with Promoted Energy Storage Capability for Wearable Aqueous Rechargeable NiCo‐Fe Batteries

Aqueous rechargeable Ni‐Fe batteries featuring an ultra‐flat discharge plateau, low cost, and outstanding safety characteristics show promising prospects for application in wearable energy storage. In particular, fiber‐shaped Ni‐Fe batteries will enable textile‐based energy supply for wearable electronics. However, the development of fiber‐shaped Ni‐Fe batteries is currently challenged by the performance of fibrous Fe‐based anode materials. In this context, this study describes the fabrication of sulfur‐doped Fe₂O₃ nanowire arrays (S‐Fe₂O₃ NWAs) grown on carbon nanotube fibers (CNTFs) as an innovative anode material (S‐Fe₂O₃ NWAs/CNTF). Encouragingly, first‐principle calculations reveal that S‐doping in Fe₂O₃ can dramatically reduce the band gap from 2.34 to 1.18 eV and thus enhance electronic conductivity. The novel developed S‐Fe₂O₃ NWAs/CNTF electrode is further demonstrated to deliver a very high capacity of 0.81 mAh cm^?2 at 4 mA cm^?2. This value is almost sixfold higher than that of the pristine Fe₂O₃ NWAs/CNTF electrode. When a cathode containing zinc‐nickel‐cobalt oxide (ZNCO)@Ni(OH)₂ NWAs heterostructures is used, 0.46 mAh cm^?2 capacity and 67.32 mWh cm^?3 energy density are obtained for quasi‐solid‐state fiber‐shaped NiCo‐Fe batteries, which outperform most state‐of‐the‐art fiber‐shaped aqueous rechargeable batteries. These findings offer an innovative and feasible route to design high‐performance Fe‐based anodes and may inspire new development for the next‐generation wearable Ni‐Fe batteries.