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1.
The preparation of novel one‐dimensional core–shell Fe/Fe2O3 nanowires as anodes for high‐performance lithium‐ion batteries (LIBs) is reported. The nanowires are prepared in a facile synthetic process in aqueous solution under ambient conditions with subsequent annealing treatment that could tune the capacity for lithium storage. When this hybrid is used as an anode material for LIBs, the outer Fe2O3 shell can act as an electrochemically active material to store and release lithium ions, whereas the highly conductive and inactive Fe core functions as nothing more than an efficient electrical conducting pathway and a remarkable buffer to tolerate volume changes of the electrode materials during the insertion and extraction of lithium ions. The core–shell Fe/Fe2O3 nanowire maintains an excellent reversible capacity of over 767 mA h g?1 at 500 mA g?1 after 200 cycles with a high average Coulombic efficiency of 98.6 %. Even at 2000 mA g?1, a stable capacity as high as 538 mA h g?1 could be obtained. The unique composition and nanostructure of this electrode material contribute to this enhanced electrochemical performance. Due to the ease of large‐scale fabrication and superior electrochemical performance, these hybrid nanowires are promising anode materials for the next generation of high‐performance LIBs.  相似文献   

2.
By using carbon nanotubes (CNTs) as a shape template and glucose as a carbon precursor and structure‐directing agent, CNT@Fe3O4@C porous core/sheath coaxial nanocables have been synthesized by a simple one‐pot hydrothermal process. Neither a surfactant/ligand nor a CNT pretreatment is needed in the synthetic process. A possible growth mechanism governing the formation of this nanostructure is discussed. When used as an anode material of lithium‐ion batteries, the CNT@Fe3O4@C nanocables show significantly enhanced cycling performance, high rate capability, and high Coulombic efficiency compared with pure Fe2O3 particles and Fe3O4/CNT composites. The CNT@Fe3O4@C nanocables deliver a reversible capacity of 1290 mA h g?1 after 80 cycles at a current density of 200 mA g?1, and maintain a reversible capacity of 690 mA h g?1 after 200 cycles at a current density of 2000 mA g?1. The improved lithium storage behavior can be attributed to the synergistic effect of the high electronic conductivity support and the inner CNT/outer carbon buffering matrix.  相似文献   

3.
A mesoporous flake‐like manganese‐cobalt composite oxide (MnCo2O4) is synthesized successfully through the hydrothermal method. The crystalline phase and morphology of the materials are characterized by X‐ray diffraction, field‐emission scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller methods. The flake‐like MnCo2O4 is evaluated as the anode material for lithium‐ion batteries. Owing to its mesoporous nature, it exhibits a high reversible capacity of 1066 mA h g?1, good rate capability, and superior cycling stability. As an electrode material for supercapacitors, the flake‐like MnCo2O4 also demonstrates a high supercapacitance of 1487 F g?1 at a current density of 1 A g?1, and an exceptional cycling performance over 2000 charge/discharge cycles.  相似文献   

4.
Nanostructured NiCo2O4 is directly grown on the surface of three‐dimensional graphene‐coated nickel foam (3D‐GNF) by a facile electrodeposition technique and subsequent annealing. The resulting NiCo2O4 possesses a distinct flower or sheet morphology, tuned by potential or current variation electrodeposition, which are used as binder‐free lithium‐ion battery anodes for the first time. Both samples exhibit high lithium storage capacity, profiting from the unique binder‐free electrode structures. The flower‐type NiCo2O4 demonstrates high reversible discharge capacity (1459 mAh g?1 at 200 mA g?1) and excellent cyclability with around 71 % retention of the reversible capacity after 60 cycles, which are superior to the sheet‐type NiCo2O4. Such superb performance can be attributed to high volume utilization efficiency with unique morphological character, a well‐preserved connection between the active materials and the current collector, a short lithium‐ion diffusion path, and fast electrolyte transfer in the binder‐free NiCo2O4‐coated 3D graphene structure. The simple preparation process and easily controllable morphology make the binder‐free NiCo2O4/3D‐GNF hybrid a potential material for commercial applications.  相似文献   

5.
Carbon nanomaterials, especially graphene and carbon nanotubes, are considered to be favorable alternatives to graphite‐based anodes in lithium‐ion batteries, owing to their high specific surface area, electrical conductivity, and excellent mechanical flexibility. However, the limited number of storage sites for lithium ions within the sp2‐carbon hexahedrons leads to the low storage capacity. Thus, rational structure design is essential for the preparation of high‐performance carbon‐based anode materials. Herein, we employed flexible single‐walled carbon nanotubes (SWCNTs) with ultrahigh electrical conductivity as a wrapper for 3D graphene foam (GF) by using a facile dip‐coating process to form a binary network structure. This structure, which offered high electrical conductivity, enlarged the electrode/electrolyte contact area, shortened the electron‐/ion‐transport pathways, and allowed for efficient utilization of the active material, which led to improved electrochemical performance. When used as an anode in lithium‐ion batteries, the SWCNT‐GF electrode delivered a specific capacity of 953 mA h g?1 at a current density of 0.1 A g?1 and a high reversible capacity of 606 mA h g?1 after 1000 cycles, with a capacity retention of 90 % over 1000 cycles at 1 A g?1 and 189 mA h g?1 after 2200 cycles at 5 A g?1.  相似文献   

6.
Considerable lithium‐driven volume changes and loss of crystallinity on cycling have impeded the sustainable use of transition metal oxides (MOs) as attractive anode materials for advanced lithium‐ion batteries that have almost six times the capacity of carbon per unit volume. Herein, Co3O4 was used as a model MO in a facile process involving two pyrolysis steps for in situ encapsulation of nanosized MO in porous two‐dimensional graphitic carbon nanosheets (2D‐GCNs) with high surface areas and abundant active sites to overcome the above‐mentioned problems. The proposed method is inexpensive, industrially scalable, and easy to operate with a high yield. TEM revealed that the encaged Co3O4 is well separated and uniformly dispersed with surrounding onionlike graphitic layers. By taking advantage of the high electronic conductivity and confinement effect of the surrounding 2D‐GCNs, a hierarchical GCNs‐coated Co3O4 (Co3O4@GCNs) anode with 43.5 wt % entrapped active nanoparticles delivered a remarkable initial specific capacity of 1816 mAh g?1 at a current density of 100 mA g?1. After 50 cycles, the retained capacity is as high as 987 mAh g?1. When the current density was increased to 1000 mA g?1, the anode showed a capacity retention of 416 mAh g?1. Enhanced reversible rate capability and prolonged cycling stability were found for Co3O4@GCN compared to pure GCNs and Co3O4. The Co3O4@GCNs hybrid holds promise as an efficient candidate material for anodes due to its low cost, environmentally friendly nature, high capacity, and stability.  相似文献   

7.
The synthesis of nanoporous graphene by a convenient carbon nanofiber assisted self‐assembly approach is reported. Porous structures with large pore volumes, high surface areas, and well‐controlled pore sizes were achieved by employing spherical silica as hard templates with different diameters. Through a general wet‐immersion method, transition‐metal oxide (Fe3O4, Co3O4, NiO) nanocrystals can be easily loaded into nanoporous graphene papers to form three‐dimensional flexible nanoarchitectures. When directly applied as electrodes in lithium‐ion batteries and supercapacitors, the materials exhibited superior electrochemical performances, including an ultra‐high specific capacity, an extended long cycle life, and a high rate capability. In particular, nanoporous Fe3O4–graphene composites can deliver a reversible specific capacity of 1427.5 mAh g?1 at a high current density of 1000 mA g?1 as anode materials in lithium‐ion batteries. Furthermore, nanoporous Co3O4–graphene composites achieved a high supercapacitance of 424.2 F g?1. This work demonstrated that the as‐developed freestanding nanoporous graphene papers could have significant potential for energy storage and conversion applications.  相似文献   

8.
A composite of highly dispersed Fe3O4 nanoparticles (NPs) anchored in three‐dimensional hierarchical porous carbon networks (Fe3O4/3DHPC) as an anode material for lithium‐ion batteries (LIBs) was prepared by means of a deposition technique assisted by a supercritical carbon dioxide (scCO2)‐expanded ethanol solution. The as‐synthesized Fe3O4/3DHPC composite exhibits a bimodal porous 3D architecture with mutually connected 3.7 nm mesopores defined in the macroporous wall on which a layer of small and uniform Fe3O4 NPs was closely coated. As an anode material for LIBs, the Fe3O4/3DHPC composite with 79 wt % Fe3O4 (Fe3O4/3DHPC‐79) delivered a high reversible capacity of 1462 mA h g?1 after 100 cycles at a current density of 100 mA g?1, and maintained good high‐rate performance (728, 507, and 239 mA h g?1 at 1, 2, and 5 C, respectively). Moreover, it showed excellent long‐term cycling performance at high current densities, 1 and 2 A g?1. The enhanced lithium‐storage behavior can be attributed to the synergistic effect of the porous support and the homogeneous Fe3O4 NPs. More importantly, this straightforward, highly efficient, and green synthetic route will definitely enrich the methodologies for the fabrication of carbon‐based transition‐metal oxide composites, and provide great potential materials for additional applications in supercapacitors, sensors, and catalyses.  相似文献   

9.
An organo‐functionalized polyoxometalate (POM)–pyrene hybrid (Py‐Anderson) has been used for noncovalent functionalization of carbon nanotubes (CNTs) to give a Py‐Anderson‐CNT nanocomposite through π–π interactions. The as‐synthesized nanocomposite was used as the anode material for lithium‐ion batteries, and shows higher discharge capacities and better rate capacity and cycling stability than the individual components. When the current density was 0.5 mA cm?2, the nanocomposite exhibited an initial discharge capacity of 1898.5 mA h g?1 and a high discharge capacity of 665.3 mA h g?1 for up to 100 cycles. AC impedance spectroscopy provides insight into the electrochemical properties and the charge‐transfer mechanism of the Py‐Anderson‐CNTs electrode.  相似文献   

10.
Heteroatom doping is an effective method to adjust the electrochemical behavior of carbonaceous materials. In this work, boron‐doped, carbon‐coated SnO2/graphene hybrids (BCTGs) were fabricated by hydrothermal carbonization of sucrose in the presence of SnO2/graphene nanosheets and phenylboronic acid or boric acid as dopant source and subsequent thermal treatment. Owing to their unique 2D core–shell architecture and B‐doped carbon shells, BCTGs have enhanced conductivity and extra active sites for lithium storage. With phenylboronic acid as B source, the resulting hybrid shows outstanding electrochemical performance as the anode in lithium‐ion batteries with a highly stable capacity of 1165 mA h g?1 at 0.1 A g?1 after 360 cycles and an excellent rate capability of 600 mA h g?1 at 3.2 A g?1, and thus outperforms most of the previously reported SnO2‐based anode materials.  相似文献   

11.
A pure inorganic 2D network molybdophosphate, [Mn3Mo12O24(OH)6(HPO3)8(H2O)6]4? ( 1 a ), synthesized through microwave irradiation with the existence of Mn2+ and organic cations and isolated as [(CH3)2NH2]3Na[Mn3Mo12O24(OH)6(HPO3)8(H2O)6] ? 12 H2O ( 1 ), is found to possess highly enhanced performance in lithium‐ion batteries’ anode materials. The molecule shows multielectron redox properties suitable for producing anode materials with a specific capacity of 602 mA h g?1 at 100 mA g?1 after 50 cycles in lithium‐ion batteries, although its specific capacity is the highest among all the reported pure inorganic 2D polyoxometalates to date, the cyclic stability is not that satisfactory. A hybrid nanocomposite of this 2D network and polypyrrole cations effectively reduces the capacity fading in initial cycles, and increases the stability and improves the electrochemical performance of lithium‐ion batteries as well.  相似文献   

12.
Cu3V2O8 nanoparticles with particle sizes of 40–50 nm have been prepared by the co‐precipitation method. The Cu3V2O8 electrode delivers a discharge capacity of 462 mA h g?1 for the first 10 cycles and then the specific capacity, surprisingly, increases to 773 mA h g?1 after 50 cycles, possibly as a result of extra lithium interfacial storage through the reversible formation/decomposition of a solid electrolyte interface (SEI) film. In addition, the electrode shows good rate capability with discharge capacities of 218 mA h g?1 under current densities of 1000 mA g?1. Moreover, the lithium storage mechanism for Cu3V2O8 nanoparticles is explained on the basis of ex situ X‐ray diffraction data and high‐resolution transmission electron microscopy analyses at different charge/discharge depths. It was evidenced that Cu3V2O8 decomposes into copper metal and Li3VO4 on being initially discharged to 0.01 V, and the Li3VO4 is then likely to act as the host for lithium ions in subsequent cycles by means of the intercalation mechanism. Such an “in situ” compositing phenomenon during the electrochemical processes is novel and provides a very useful insight into the design of new anode materials for application in lithium‐ion batteries.  相似文献   

13.
Bipolar redox organics have attracted interest as electrode materials for energy storage owing to their flexibility, sustainability and environmental friendliness. However, an understanding of their application in all‐organic batteries, let alone dual‐ion batteries (DIBs), is in its infancy. Herein, we propose a strategy to screen a variety of phthalocyanine‐based bipolar organics. The self‐polymerizable bipolar Cu tetraaminephthalocyanine (CuTAPc) shows multifunctional applications in various energy storage systems, including lithium‐based DIBs using CuTAPc as the cathode material, graphite‐based DIBs using CuTAPc as the anode material and symmetric DIBs using CuTAPc as both the cathode and anode materials. Notably, in lithium‐based DIBs, the use of CuTAPc as the cathode material results in a high discharge capacity of 236 mAh g?1 at 50 mA g?1 and a high reversible capacity of 74.3 mAh g?1 after 4000 cycles at 4 A g?1. Most importantly, a high energy density of 239 Wh kg?1 and power density of 11.5 kW kg?1 can be obtained in all‐organic symmetric DIBs.  相似文献   

14.
Nanoporous ZnMn2O4 nanorods have been successfully synthesized by calcining β-MnO2/ZIF-8 precursors (ZIF-8 is a type of metal–organic framework). If measured as an anode material for lithium-ion batteries, the ZnMn2O4 nanorods exhibit an initial discharge capacity of 1792 mA h g−1 at 200 mA g−1, and an excellent reversible capacity of 1399.8 mA h g−1 after 150 cycles (78.1 % retention of the initial discharge capacity). Even at 1000 mA g−1, the reversible capacity is still as high as 998.7 mA h g−1 after 300 cycles. The remarkable lithium-storage performance is attributed to the one-dimensional nanoporous structure. The nanoporous architecture not only allows more lithium ions to be stored, which provides additional interfacial lithium-storage capacity, but also buffers the volume changes, to a certain degree, during the Li+ insertion/extraction process. The results demonstrate that nanoporous ZnMn2O4 nanorods with superior lithium-storage performance have the potential to be candidates for commercial anode materials in lithium-ion batteries.  相似文献   

15.
Single‐walled carbon nanotubes (SWNTs) covalently functionalized with redox‐active organo‐modified polyoxometalate (POM) clusters have been synthesized and employed as electrode materials in lithium ion batteries. The Anderson cluster [MnMo6O24]9? is functionalized with Tris (NH2C(CH2OH)3) moieties, giving the new organic–inorganic hybrid [N(nC4H9)4]3[MnMo6O18{(OCH2)3CNH2}2]. The compound is then covalently attached to carboxylic acid‐functionalized SWNTs by amide bond formation and the stability of this nanocomposite is confirmed by various spectroscopic methods. Electrochemical analyses show that the nanocomposite displays improved performance as an anode material in lithium ion batteries compared with the individual components, that is, SWNTs and/or Anderson clusters. High discharge capacities of up to 932 mAh g?1 at a current density of 0.5 mA cm?2 can be observed, together with high long‐term cycling stability and decreased electrochemical impedance. Chemisorption of the POM cluster on the SWNTs is shown to give better electrode performance than the purely physisorbed analogues.  相似文献   

16.
《中国化学》2017,35(10):1575-1585
Binder‐free, nano‐sized needlelike MnO2 ‐submillimeter‐sized reduced graphene oxide (nMnO2‐srGO ) hybrid films with abundant porous structures were fabricated through electrophoretic deposition and subsequent thermal annealing at 500 °C for 2 h. The as‐prepared hybrid films exhibit a unique hierarchical morphology, in which nMnO2 with a diameter of 20—50 nm and a length of 300—500 nm is randomly anchored on both sides of srGO . When evaluated as binder‐free anodes for lithium‐ion half‐cell, the nMnO2‐srGO composites with a content of 76.9 wt% MnO2 deliver a high capacity of approximately 1652.2 mA •h•g−1 at a current density of 0.1 A•g−1 after 200 cycles. The high capacity remains at 616.8 mA •h•g−1 (ca. 65.1% capacity retention) at a current density as high as 4 A•g−1. The excellent electrochemical performance indicates that the nMnO2‐srGO hybrid films could be a promising anode material for lithium ion batteries (LIBs ).  相似文献   

17.
In the work, a facile and green two‐step synthetic strategy was purposefully developed to efficiently fabricate hierarchical shuttle‐shaped mesoporous ZnFe2O4 microrods (MRs) with a high tap density of ~0.85 g cm3, which were assembled by 1D nanofiber (NF) subunits, and further utilized as a long‐life anode for advanced Li‐ion batteries. The significant role of the mixed solvent of glycerin and water in the formation of such hierarchical mesoporous MRs was systematically investigated. After 488 cycles at a large current rate of 1000 mA g?1, the resulting ZnFe2O4 MRs with high loading of ~1.4 mg per electrode still preserved a reversible capacity as large as ~542 mAh g?1. Furthermore, an initial charge capacity of ~1150 mAh g?1 is delivered by the ZnFe2O4 anode at 100 mA g?1, resulting in a high Coulombic efficiency of ~76 % for the first cycle. The superior Li‐storage properties of the as‐obtained ZnFe2O4 were rationally associated with its mesoprous micro‐/nanostructures and 1D nanoscaled building blocks, which accelerated the electron transportation, facilitated Li+ transfer rate, buffered the large volume variations during repeated discharge/charge processes, and provided rich electrode–electrolyte sur‐/interfaces for efficient lithium storage, particularly at high rates.  相似文献   

18.
High‐temperature flame spray pyrolysis is employed for finding highly efficient nanomaterials for use in lithium‐ion batteries. CoOx‐FeOx nanopowders with various compositions are prepared by one‐pot high‐temperature flame spray pyrolysis. The Co and Fe components are uniformly distributed over the CoOx‐FeOx composite powders, irrespective of the Co/Fe mole ratio. The Co‐rich CoOx‐FeOx composite powders with Co/Fe mole ratios of 3:1 and 2:1 have mixed crystal structures with CoFe2O4 and Co3O4 phases. However, Co‐substituted magnetite composite powders prepared from spray solutions with Co and Fe components in mole ratios of 1:3, 1:2, and 1:1 have a single phase. Multicomponent CoOx‐FeOx powders with a Co/Fe mole ratio of 2:1 and a mixed crystal structure with Co3O4 and CoFe2O4 phases show high initial capacities and good cycling performance. The stable reversible discharge capacities of the composite powders with a Co/Fe mole ratio of 2:1 decrease from 1165 to 820 mA h g?1 as the current density is increased from 500 to 5000 mA g?1; however, the discharge capacity again increases to 1310 mA h g?1 as the current density is restored to 500 mA g?1.  相似文献   

19.
Volume expansion and poor conductivity are two major obstacles that hinder the pursuit of the lithium‐ion batteries with long cycling life and high power density. Herein, we highlight a misfit compound PbNbS3 with a soft/rigid superlattice structure, confirmed by scanning tunneling microscopy and electrochemical characterization, as a promising anode material for high performance lithium‐ion batteries with optimized capacity, stability, and conductivity. The soft PbS sublayers primarily react with lithium, endowing capacity and preventing decomposition of the superlattice structure, while the rigid NbS2 sublayers support the skeleton and enhance the migration of electrons and lithium ions, as a result leading to a specific capacity of 710 mAh g?1 at 100 mA g?1, which is 1.6 times of NbS2 and 3.9 times of PbS. Our finding reveals the competitive strategy of soft/rigid structure in lithium‐ion batteries and broadens the horizons of single‐phase anode material design.  相似文献   

20.
Silver molybdate, Ag2Mo2O7, has been prepared by a conventional solid‐state reaction. Its electrochemical properties as an anode material for sodium‐ion batteries (SIBs) have been comprehensively examined by means of galvanostatic charge–discharge cycling, cyclic voltammetry, and rate performance measurements. At operating voltages between 3.0 and 0.01 V, the electrode delivered a reversible capacity of nearly 190 mA h g?1 at a current density of 20 mA g?1 after 70 cycles. Ag2Mo2O7 also demonstrated a good rate capability and long‐term cycle stability, the capacity reaching almost 100 mA h g?1 at a current density of 500 mA g?1, with a capacity retention of 55 % over 1000 cycles. Moreover, the sodium storage process of Ag2Mo2O7 has been investigated by means of ex situ XRD, Raman spectroscopy, and HRTEM. Interestingly, the anode decomposes into Ag metal and Na2MoO4 during the initial discharge process, and then Na+ ions are considered to be inserted into/extracted from the Na2MoO4 lattice in the subsequent cycles governed by an intercalation/deintercalation mechanism. Ex situ HRTEM images revealed that Ag metal not only remains unchanged during the sodiation/desodiation processes, but is well dispersed throughout the amorphous matrix, thereby greatly improving the electronic conductivity of the working electrode. The “in situ” decomposition behavior of Ag2Mo2O7 is distinct from that of chemically synthesized, metal‐nanoparticle‐coated electrode materials, and provides strong supplementary insight into the mechanism of such new anode materials for SIBs and may set a precedent for the design of further materials.  相似文献   

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