Enhanced electrode performance of Fe2O3 nanoparticle-decorated nanomesh graphene as anodes for lithium-ion batteries

General Construction of 2D Ordered Mesoporous Iron-Based Metal-Organic Nanomeshes

Nanomeshes with highly regular, permeable pores in plane, combining the exceptional porous architectures with intrinsic properties of 2D materials, have attracted increasing attention in recent years. Herein, a series of 2D ultrathin metal-organic nanomeshes with ordered mesopores is obtained by a self-assembly method, including metal phosphate and metal phosphonate. The resultant mesoporous ferric phytate nanomeshes feature unique 2D ultrathin monolayer morphologies (≈9 nm thickness), hexagonally ordered, permeable mesopores of ≈16 nm, as well as improved surface area and pore volume. Notably, the obtained ferric phytate nanomeshes can directly in situ convert into mesoporous sulfur-doped metal phosphonate nanomeshes by serving as an unprecedented reactive self-template. Furthermore, as advanced anode materials for Li-ion batteries, they deliver excellent capacity, good rate capability, and cycling performance, greatly exceeding the similar metal phosphate-based materials reported previously, resulting from their unique 2D ultrathin mesoporous structure. Therefore, the work will pave an avenue for constructing the other 2D ordered mesoporous materials, and thus offer new opportunities for them in diverse areas.

Conductance Tunable Suspended Graphene Nanomesh by Helium Ion Beam Milling

This paper demonstrates that the electrical properties of suspended graphene nanomesh (GNM) can be tuned by systematically changing the porosity with helium ion beam milling (HIBM). The porosity of the GNM is well-controlled by defining the pitch of the periodic nanopores. The defective region surrounding the individual nanopores after HIBM, which limits the minimum pitch achievable between nanopores for a certain dose, is investigated and reported. The exponential relationship between the thermal activation energy (E_A) and the porosity is found in the GNM devices. Good E_A tuneability observed from the GNMs provides a new approach to the transport gap engineering beyond the conventional nanoribbon method.

Capacitive Sodium-Ion Storage Based on Double-Layered Mesoporous Graphene with High Capacity and Charging/Discharging Rate

Sodium-ion batteries (SIBs) are regarded as an ideal alternative to lithium-ion batteries, but the larger radius of Na⁺ compared with Li⁺ results in lower energy density, shorter cycle life, and sluggish kinetics of SIBs. Therefore, it is of significant importance to explore appropriate Na⁺ storage materials with high capacity and fast Na⁺ transport kinetics. Herein, doublelayered mesoporous graphene nanosheets codoped with oxygen and nitrogen (O,N-MGNSs) were developed as a new cathode material with high Na⁺ storage capacity and fast ion-transport kinetics for SIBs. The codoping of MGNSs with oxygen and nitrogen by in situ chemical vapor deposition endowed them with a hierarchical porous network, robust structures, good conductivity, and abundant functional groups. The O,N-MGNSs could host Na⁺ in two ways: surface adsorption and surface redox reaction, and this endowed them with high Na⁺ storage capacity and fast charging/discharging rates in SIBs. Electrochemical results revealed that the O,N-MGNSs delivered a reversible capacity of 156 mAh g^-1 at a current density of 0.5 A g^-1 (corresponding to a rate of 3 C) between 1.5 and 4.2 V and exhibited a high cycling stability (95 % capacity retention at 1 A g^-1 for more than 1000 cycles).

Pseudocapacitive Behaviors of Li2FeTiO4/C Hybrid Porous Nanotubes for Novel Lithium-Ion Battery Anodes with Superior Performances

Hybrid nanotubes of cation disordered rock salt structured Li₂FeTiO₄ nanoparticles embedded in porous CNTs were developed. Such unique hybrids with continuous 3D electron transportation paths and isolated small particles have been shown to be an ideal architecture that brought out enhanced electrochemical performances. Meanwhile, they exhibited improved extrinsic capacitive characteristics. In addition, we demonstrate a successful example to use cathode active material as anode for lithium-ion batteries (LIBs). More importantly, our hybrids had much superior electrochemical performances than most of the reported Li₄Ti₅O₁₂-based nanocomposites. Therefore, it is concluded that Li₂FeTiO₄ can be a prospective anode material for LIBs.

FeO x -Based Materials for Electrochemical Energy Storage

Iron oxides (FeO x ), such as Fe2O3 and Fe3O4 materials, have attracted much attention because of their rich abundance, low cost, and environmental friendliness. However, FeO x , which is similar to most transition metal oxides, possesses a poor rate capability and cycling life. Thus, FeO x -based materials consisting of FeO x , carbon, and metal-based materials have been widely explored. This article mainly discusses FeO x -based materials (Fe2O3 and Fe3O4) for electrochemical energy storage applications, including supercapacitors and rechargeable batteries (e.g., lithium-ion batteries and sodium-ion batteries). Furthermore, future perspectives and challenges of FeO x -based materials for electrochemical energy storage are briefly discussed.

MnWO4 nanoparticles as advanced anodes for lithium-ion batteries: F-doped enhanced lithiation/delithiation reversibility and Li-storage properties

F-Doped MnWO4 nano-particles were synthesized by a one-pot hydrothermal reaction. When evaluated as an electrode material for a Li ion battery, the F-doped nano-MnWO4 delivers a theoretical capacity of 708 mA h g-1 and a long cycle life, as demonstrated by more than 85% capacity retention when cycled for 150 cycles.

Structurally Controlled Large-Area 10 nm Pitch Graphene Nanomesh by Focused Helium Ion Beam Milling

Graphene nanomesh (GNM) is formed by patterning graphene with nanometer-scale pores separated by narrow necks. GNMs are of interest due to their potential semiconducting characteristics when quantum confinement in the necks leads to an energy gap opening. GNMs also have potential for use in phonon control and water filtration. Furthermore, physical phenomena, such as spin qubit, are predicted at pitches below 10 nm fabricated with precise structural control. Current GNM patterning techniques suffer from either large dimensions or a lack of structural control. This work establishes reliable GNM patterning with a sub-10 nm pitch and an < 4 nm pore diameter by the direct helium ion beam milling of suspended monolayer graphene. Due to the simplicity of the method, no postpatterning processing is required. Electrical transport measurements reveal an effective energy gap opening of up to ∼450 meV. The reported technique combines the highest resolution with structural control and opens a path toward GNM-based, room-temperature semiconducting applications.

Enhancement of Electrochemical Performance by the Oxygen Vacancies in Hematite as Anode Material for Lithium-Ion Batteries

The application of hematite in lithium-ion batteries (LIBs) has been severely limited because of its poor cycling stability and rate performance. To solve this problem, hematite nanoparticles with oxygen vacancies have been rationally designed by a facile sol-gel method and a sequential carbon-thermic reduction process. Thanks to the existence of oxygen vacancies, the electrochemical performance of the as-obtained hematite nanoparticles is greatly enhancing. When used as the anode material in LIBs, it can deliver a reversible capacity of 1252 mAh g^-1 at 2 C after 400 cycles. Meanwhile, the as-obtained hematite nanoparticles also exhibit excellent rate performance as compared to its counterparts. This method not only provides a new approach for the development of hematite with enhanced electrochemical performance but also sheds new light on the synthesis of other kinds of metal oxides with oxygen vacancies.

Highly Efficient High-Pressure Homogenization Approach for Scalable Production of High-Quality Graphene Sheets and Sandwich-Structured α-Fe2O3/Graphene Hybrids for High-Performance Lithium-Ion Batteries

A highly efficient and continuous high-pressure homogenization (HPH) approach is developed for scalable production of graphene sheets and sandwich-structured α-Fe₂O₃/graphene hybrids by liquid-phase exfoliation of stage-1 FeCl₃-based graphite intercalation compounds (GICs). The enlarged interlayer spacing of FeCl₃-GICs facilitates their efficient exfoliation to produce high-quality graphene sheets. Moreover, sandwich-structured α-Fe₂O₃/few-layer graphene (FLG) hybrids are readily fabricated by thermally annealing the FeCl₃ intercalated FLG sheets. As an anode material of Li-ion battery, α-Fe₂O₃/FLG hybrid shows a satisfactory long-term cycling performance with an excellent specific capacity of 1100.5 mA h g^-1 after 350 cycles at 200 mA g^-1. A high reversible capacity of 658.5 mA h g^-1 is achieved after 200 cycles at 1 A g^-1 and maintained without notable decay. The satisfactory cycling stability and the outstanding capability of α-Fe₂O₃/FLG hybrid are attributed to its unique sandwiched structure consisting of highly conducting FLG sheets and covalently anchored α-Fe₂O₃ particles. Therefore, the highly efficient and scalable preparation of high-quality graphene sheets along with the excellent electrochemical properties of α-Fe₂O₃/FLG hybrids makes the HPH approach promising for producing high-performance graphene-based energy storage materials.

Metastable Marcasite-FeS2 as a New Anode Material for Lithium Ion Batteries: CNFs-Improved Lithiation/Delithiation Reversibility and Li-Storage Properties

Marcasite (m-FeS₂) exhibits higher electronic conductivity than that of pyrite (p-FeS₂) because of its lower semiconducting gap (0.4 vs 0.7 eV). Meanwhile, as demonstrates stronger Fe-S bonds and less S-S interactions, the m-FeS₂ seems to be a better choice for electrode materials compared to p-FeS₂. However, the m-FeS₂ has been seldom studied due to its sophisticated synthetic methods until now. Herein, a hierarchical m-FeS₂ and carbon nanofibers composite (m-FeS₂/CNFs) with grape-cluster structure was designed and successfully prepared by a straightforward hydrothermal method. When evaluated as an electrode material for lithium ion batteries, the m-FeS₂/CNFs exhibited superior lithium storage properties with a high reversible capacity of 1399.5 mAh g^-1 after 100 cycles at 100 mA g^-1 and good rate capability of 782.2 mAh g^-1 up to 10 A g^-1. The Li-storage mechanism for the lithiation/delithiation processes of m-FeS₂/CNFs was systematically investigated by ex situ powder X-ray diffraction patterns and scanning electron microscopy. Interestingly, the hierarchical m-FeS₂ microspheres assembled by small FeS₂ nanoparticles in the m-FeS₂/CNFs composite converted into a mimosa with leaves open shape during Li⁺ insertion process and vice versa. Accordingly, a "CNFs accelerated decrystallization-recrystallization" mechanism was proposed to explain such morphology variations and the decent electrochemical performance of m-FeS₂/CNFs.

Suppression of degradation for lithium iron phosphate cylindrical batteries by nano silicon surface modification

Si surface modification gets improved electrochemical performances for 18 650 cylindrical cells, especially at elevated temperature, which is attributed to the fact that Si can enable the LiFePO₄ electrodes to suppress battery degradation.

Rational design and controllable preparation of holey MnO2 nanosheets

A novel technique for the design and controllable preparation of holey MnO₂ nanosheets was first developed by an in situ redox reaction between the MnO₂ nanosheets and adsorbed Fe²⁺ ions at room temperature, in which Fe²⁺ ions originated from a redox reaction between Cu wire and Fe³⁺ ions.

Hierarchical porous MnO/graphene composite aerogel as high-performance anode material for lithium ion batteries

MnO/graphene composite anode material with hierarchical pore structure shows high capacity, excellent rate capability and stability.

Novel Bake-in-Salt Method for the Synthesis of Mesoporous Mn3O4@C Networks with Superior Cycling Stability and Rate Performance

The commercial applications of Mn₃O₄ in lithium ion batteries (LIBs) are greatly restricted because of the low electrical conductivity and poor cycling stability at high current density. To overcome these drawbacks, mesoporous Mn₃O₄@C networks were designed and synthesized via an improved bake-in-salt method using NaCl as the assistant salt, and without the protection of inert gas. The added NaCl plays a versatile role during the synthetic process, including the heat conducting medium, removable hard template and protective layer. Because of the homogeneous distribution of Mn₃O₄ nanoparticles within the carbon matrix, the as-prepared Mn₃O₄@C networks show excellent cycling stability in LIBs. After cycling for 950 times at a current density of 1 A g^-1, the discharge capacity of the as-prepared Mn₃O₄@C networks is determined to be 754.4 mA h g^-1, showing superior cycling stability as compared to its counterparts. The valuable and promising method, simple synthetic procedure and excellent cycling stability of the as-prepared Mn₃O₄@C networks makes it a promising candidate as the potential anode material for LIBs.

A self-assembly strategy for fabricating highly stable silicon/reduced graphene oxide anodes for lithium-ion batteries

High initial coulombic efficiency and improved cyclic stability were obtained by introducting CATB into GO and Si NPs.

2D materials for renewable energy storage devices: Outlook and challenges

We review cost-effective, clean and durable alternative energy devices based on 2D materials.

Excellent lithium ion storage property of porous MnCo2O4 nanorods

The porous MnCo₂O₄ nanorods have been successfully prepared by a simple and economic method and exhibited a high electrochemical performance.

A chemically modified graphene oxide wrapped porous hematite nano-architecture as a high rate lithium-ion battery anode material

Chemically modified graphene oxide wrapped porous hematite nanorods: an interconnected hollow network for excellent lithium storage in lithium ion batteries.

Two-Dimensional Porous Micro/Nano Metal Oxides Templated by Graphene Oxide

Novel two-dimensional (2D) porous metal oxides with micro-/nanoarchitecture have been successfully fabricated using graphene oxide (GO) as a typical sacrificial template. GO as a 2D template ensures that the growth and fusion of metal oxides nanoparticles is restricted in the 2D plane. A series of metal oxides (NiO, Fe2O3, Co3O4, Mn2O3, and NiFe2O4) with similar nanostructure were investigated using this simple method. Some of these special nanostructured materials, such as NiO, when being used as anode for lithium-ion batteries, can exhibit high specific capacity, good rate performance, and cycling stability. Importantly, this strategy of creating a 2D porous micro/nano architecture can be easily extended to controllably synthesize other binary/polynary metal oxides nanostructures for lithium-ion batteries or other applications.

Design and Synthesis of Bubble-Nanorod-Structured Fe2O3-Carbon Nanofibers as Advanced Anode Material for Li-Ion Batteries

A structure denoted as a "bubble-nanorod composite" is synthesized by introducing the Kirkendall effect into the electrospinning method. Bubble-nanorod-structured Fe2O3-C composite nanofibers, which are composed of nanosized hollow Fe2O3 spheres uniformly dispersed in an amorphous carbon matrix, are synthesized as the target material. Post-treatment of the electrospun precursor nanofibers at 500 °C under 10% H2/Ar mixture gas atmosphere produces amorphous FeOx-carbon composite nanofibers. Post-treatment of the FeOx-carbon composite nanofibers at 300 °C under air atmosphere produces the bubble-nanorod-structured Fe2O3-C composite nanofibers. The solid Fe nanocrystals formed by the reduction of FeOx are converted into hollow Fe2O3 nanospheres during the further heating process by the well-known Kirkendall diffusion process. The discharge capacities of the bubble-nanorod-structured Fe2O3-C composite nanofibers and hollow bare Fe2O3 nanofibers for the 300th cycles at a current density of 1.0 A g(-1) are 812 and 285 mA h g(-1), respectively, and their capacity retentions measured from the second cycle are 84 and 24%, respectively. The hollow nanospheres accommodate the volume change that occurs during cycling. The unique structure of the bubble-nanorod-structured Fe2O3-C composite nanofibers results in their superior electrochemical properties by improving the structural stability during long-term cycling.

Iron oxide/graphene composites as negative-electrode materials for lithium ion batteries – optimum particle size for stable performance

We synthesized Fe₂O₃/graphene composites by a hydrothermal method.

A new application of oily cold rolling mill sludge for preparing Fe2O3/graphene as anodes for lithium-ion batteries

A new application of oily cold rolling mill sludge for preparing Fe₂O₃/graphene as anodes for lithium-ion batteries.

Electrochemical fabrication of graphene nanomesh via colloidal templating

A simple fabrication of graphene nanomesh (GNM) was accomplished by arraying polystyrene (PS) spheres onto a CVD-deposited graphene, electro-deposition of carbazole units, removal of PS template and electrochemical oxidative etching. The GNM was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and Raman spectroscopy.

Controllable synthesis of graphene nanoscroll-wrapped Fe3O4 nanoparticles and their lithium-ion battery performance

The mass ratio of Fe₃O₄/GO plays an important role in determining the structure and the electrochemical performance of Fe₃O₄@GNS.

Facile synthesis of free-standing Fe2O3/carbon nanotube composite films as high-performance anodes for lithium-ion batteries

Continuous Fe nanoparticles (NPs)/carbon nanotube (CNTs) composite films have been fabricated with the CVD gas flow reaction using ferrocene as a catalyst and ethanol as a carbon precursor.

Nanoporous iron oxide@carbon composites with low carbon content as high-performance anodes for lithium-ion batteries

Nanoporous Fe₂O₃@C nanoparticles with low carbon content as high performance anodes for lithium-ion batteries.

Additive-free synthesis of In₂O₃ cubes embedded into graphene sheets and their enhanced NO₂ sensing performance at room temperature

In this report, we developed an additive-free synthesis of In2O3 cubes embedded into graphene networks with InN nanowires (InN-NWs) and graphene oxide (GO) as precursors by a facile one-step microwave-assisted hydrothermal method. In absence of GO, the InN-NWs maintained their chemical composition and original morphology upon the same treatment. At varying mass ratios of InN-NWs and GO, the different morphologies and distributions of In2O3 could be obtained on graphene sheets. The uniform distribution, which is usually considered favorable for enhanced sensing performance, was observed in In2O3 cubes/reduced graphene oxide (rGO) composites. The room-temperature NO2 sensing properties of the In2O3 cubes/rGO composites-based sensor were systematically investigated. The results revealed that the sensor exhibited a significant response to NO2 gas with a concentration lower to 1 ppm, and an excellent selectivity, even though the concentrations of interferential gases were 1000 times that of NO2. The enhanced NO2 sensing performances were attributed to the synergistic effect of uniformly distributed In2O3 cubes and graphene sheets in the unique hybrid architectures without the interfering of extra additives.

Graphene nanomesh: new versatile materials

Graphene, an atomic-scale honeycomb crystal lattice, is increasingly becoming popular because of its excellent mechanical, electrical, chemical, and physical properties. However, its zero bandgap places restrictions on its applications in field-effect transistors (FETs). Graphene nanomesh (GNM), a new graphene nanostructure with a tunable bandgap, shows more excellent performance. It can be widely applied in electronic or photonic devices such as highly sensitive biosensors, new generation of spintronics and energy materials. These illustrate significant opportunities for the industrial use of GNM, and hence they push nanoscience and nanotechnology one step toward practical applications. This review briefly describes the current status of the design, synthesis, and potential applications of GNM. Finally, the perspectives and challenges of GNM development are presented and some suggestions are made for its further development and exploration.

New synthesis of a Foamlike Fe3O4/C composite via a self-expanding process and its electrochemical performance as anode material for lithium-ion batteries

A novel foamlike Fe3O4/C composite is prepared via a sol-gel type method with gelatin as the carbon source and ferric nitrate as the iron source, following a postannealing treatment. Its lithium storage properties as anode material for a lithium-ion battery are thoroughly investigated in this work. With the interaction between ferric nitrate and gelatin, the foamlike architecture is attained through a unique self-expanding process. The Fe3O4/C composite possesses abundant porous structure along with highly dispersed Fe3O4 nanocrystal embedment in the carbon matrix. In the constructed architecture, the 3D porous network property ensures electrolyte accessibility; meanwhile, nanosized Fe3O4 promotes lithiation/delithiation, owing to numerous active sites, large electrolyte contact area, and a short lithium ion diffusion path. As a result, this Fe3O4/C composite electrode demonstrates an excellent cycling stability with a reversible capacity of 1008 mA h g(-1) over 400 cycles at 0.2C (1C = 1000 mA g(-1)), as well as a superior rate performance with reversible capacity of 660 and 580 mA h g(-1) at 3C and 5C, respectively.

Building robust carbon nanotube-interweaved-nanocrystal architecture for high-performance anode materials

Rational design of electrode materials is essential but still a challenge for lithium-ion batteries. Herein, we report the design and fabrication of a class of nanocomposite architecture featured by hierarchically structured composite particles that are built from iron oxide nanocrystals and carbon nanotubes. An aerosol spray drying process was used to synthesize this architecture. Such nanoarchitecture enhanced the ion transport and conductivity that are required for high-power anodes. The large volume changes of the anodes during lithium insertion and extraction are accommodated by the particle's resilience and internal porosity. High reversible capacities, excellent rate capability, and stable performance are attained. The synthesis process is simple and broadly applicable, providing a general approach toward high-performance energy storage materials.