Core/shell Fe3O4@Fe encapsulated in N-doped three-dimensional carbon architecture as anode material for lithium-ion batteries

Core-shell Fe₃O₄@Fe nanoparticles embedded into porous N-doped carbon nanosheets was prepared by a facile method with NaCl as hard-template. The three-dimensional carbon architecture built by carbon nanosheets enhance the conductivity of the encapsulated Fe₃O₄@Fe nanoparticles and strengthen the structure stability suffering from volume expansion during extraction and insertion of lithium ions. Rich Pores enhance the surface between electrode and electrolyte, which short the transmission path of ions and electrons. The core-shell structure with Fe as core further improves charge transferring inside particles thus lead to high capacity. The as-prepared Fe₃O₄@Fe/NC composite displays an irreversible discharge capacity of 839 mAh g^?1 at 1 A g^?1, long cycling life (722.2 mAh g^?1 after 500th cycle at 2 A g^?1) and excellent rate performance (1164.2 and 649.2 mAh g^?1 at 1 and 20 A g^?1, respectively). The outstanding electrochemical performance of the Fe₃O₄@Fe/NC composite indicates its application potential as anode material for LIBs.     

3D SnO2/sulfonated graphene composites with interpenetrating porous structure as anode material for lithium-ion batteries

Combine SnO₂ nanoparticles with some conductive carbonaceous materials has been regarded as one of the most effective strategies to solve the problems of poor conductivity and volume change. In this work, a SnO₂/sulfonated graphene composite with 3D interpenetrating porous structure (3D SnO₂/SG) was synthesized. The elaborate designed 3D SG structure not only generates an excellent electronic conductivity, but also buffers the volume expansion of the SnO₂ particles. As a result, the desirable 3D possesses enhanced performance when used as anode material in lithium battery. For example, the electrochemical results showed that the 3D SnO₂/SG presents a high reversible specific capacity (928.5 mA h g^?1 at the current density of 200 mA g^?1). Even after 120 cycles, the specific capacity of 679.7 mA h g^?1 (at the current density of 400 mA g^?1) are still maintained.     

Nanosized Zn–Sn metal composite oxide: a new anode material for Li ion battery

Abstract

The morphological evolution of nanosized Zn–Sn composite oxides, synthesised by the decomposition of ZnSn(OH)₆ precursor at temperature ranged from 300 to 800°C was investigated by using XRD and high resolution TEM. The precursor was also studied by thermal analysis. The electrochemical performance of Zn–Sn composite oxides as anode materials for Li ion batteries was measured in the form of Li/Zn–Sn composite oxides cells. The results reveal that the samples calcined at low temperatures (300 and 500°C) were amorphous Zn₂SnO₄ and SnO₂, and the samples calcined at high temperatures (720 and 800°C) were crystal Zn₂SnO₄ and SnO₂. All the samples have a high reversible specific capacity of over 800 mAh g^?1, and the first charge specific capacity is up to 903 mAh g^?1 for the sample calcined at 500°C. The charge capacity and cyclability were sensitive to the structure and composition of the electrode active materials; the samples calcined at phase transition temperature rage exhibited relatively worse electrochemical properties.     

Facile synthesis of nitrogen-doped Sn@NC composites as high-performance anodes for lithium-ion batteries

Owing to its high capacity of 994 mAh g^?1, low cost, and environmental friendliness, tin (Sn) is considered as an advanced anode material for high-capacity lithium-ion batteries (LIBs). Here, a facile strategy to fabricate core-shell structured Sn@NC composites with one-step and large-scale production is introduced in a liquid-phase reaction under room temperature. When used as anode materials for LIBs, the optimal Sn@NC composite delivers a high reversible discharge capacity of 761.2 and 476 mAh g^?1 at a current density of 200 and 1000 mA g^?1 after 200 cycles, respectively. A high capacity of 328.3 mAh g^?1 can also be obtained even at a current density of 2000 mA g^?1. The excellent cycling stability and rate performance of the composite can be ascribed to the synergistic effect of the nanometer size of Sn powder and porous structure of the carbon shell, both of which can effectively reduce the absolute volume change of electrode during the repeated charge-discharge cycles, and thus lead to excellent electrochemical performances at both rate capability and cycling life.     

Fe3O4/Ag microsheets assembled by interlaced nanothorns as high performance anode materials for lithium storage

Fe₃O₄/Ag nanocomposite is directly prepared by dealloying a well-designed FeAgAl source alloy in alkaline etching solution at room temperature. Selectively dissolving Al from FeAgAl alloy results in Fe₃O₄/Ag microsheets assembled by second order interlaced nanothorns. On account of the distinctive hierarchical micro-/nano-structure and the hybridization of well conductive Ag, Fe₃O₄/Ag composite shows much improved lithium storage performances with higher capacities, cycling stability, and coulombic efficiency compared with the pure Fe₃O₄ anode. Even the current rate is as high as 1 A g^?1, the capacity of Fe₃O₄/Ag composite still exceeds 600 mA h g^?1 after cycling 500 cycles compared with the remained value of only 294.8 mA h g^?1 for pure Fe₃O₄. Moreover, Fe₃O₄/Ag composite presents the excellent rate capabilities at whether low or high current densities. Owing to the superiorities of excellent properties and handy preparation, the Fe₃O₄/Ag anode exhibits encouraging prospect for lithium ion batteries.     

Enhanced electrochemical lithium storage performance of Mg2FeH6 anode with TiO2 coating

Light-weight metal hydrides are potential high-capacity conversion anode materials for lithium-ion batteries, but the poor reaction reversibility and cyclic stability of hydride anodes need to be improved. In this work, the ternary hydride Mg₂FeH₆ was composited with the graphite (G) by ball-milling, and the Mg₂FeH₆-G composite electrode was further coated with amorphous TiO₂ film by magnetron sputtering. The resultant Mg₂FeH₆-G/TiO₂ electrode exhibited a stable charge capacity of 412 mAh g^?1 over 100 cycles, which is much higher than 46 mAh g^?1 at 20th cycle for the pure Mg₂FeH₆ electrode, or 185 mAh g^?1 at 100th cycle for the Mg₂FeH₆-G electrode. There is only little capacity degradation after 20 cycles for the Mg₂FeH₆-G/TiO₂ electrode and the charge capacity retention is 84.7% after 100 cycles. The remarkable improvement in the cyclic stability of Mg₂FeH₆-G/TiO₂ electrode is mainly attributed to the dense TiO₂ coating that maintains the structural integrity of electrode during cycling. The TiO₂ coating also prevents the direct contact of high active LiH/MgH₂ with the liquid electrolyte, and thus ensures the high reversibility of conversion reaction of MgH₂ during cycling.     

Electroless-plated tin compounds on carbonaceous mixture as anode for lithium-ion battery

A composite anode materials was prepared that contained tin compounds of Sn₆O₄(OH)₄, SnO₂ and Sn₃PO₄ on the surface of carbonaceous mixture mesophase graphite particles (MGP) and nature graphite (NG). The nanosize tin compounds were electrolessly plated from aqueous solutions onto the carbonaceous mixture. The morphology and structure of tin compounds were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that the tin compounds particle size was a crucial factor to improve Sn compounds/Carbon composite anodes for cyclability and reversible capacity. The homogeneous dispersion and smaller particle size of tin compounds was attributed to the additive of NG. As the carbonaceous substrate was C-C mixture carbon, the particle size of Sn compounds was about 20-30 nm. However, the particle size was 100-200 nm, as the carbon substrate was singular MGP. Electrochemical performance test of the Sn compounds/C-C composite electrode shows the maximum specific charge capacity of 583 mAh g⁻¹ at the 5th cycle. The charge capacity retention of Sn compounds/C-C electrode was 85% after 20 cycles. The reversible capacity of Sn compounds/C-C electrode increased 292 and 97 mAh g⁻¹ more than pristine (NG + MGP) electrode and Sn compounds/C electrode at the 5th cycle, respectively.     

Synthesis of NiS coated Fe3O4 nanoparticles as high-performance positive materials for alkaline nickel-iron rechargeable batteries

In this paper, ethyl xanthate nickel (EXN) was used as nickel and sulfur sources to modify Fe₃O₄ powder nanoparticles dissolved in pyridine. After short heat treatments, the generated NiS nanoparticles were not only compactly and uniformly coated on the surface of Fe₃O₄ but also induced the decreased particle size of Fe₃O₄. The microstructure, morphology and particle size of the resulting NiS coated Fe₃O₄ particles were characterized X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and Raman spectroscopy. The results showed that thickness of the NiS coating on Fe₃O₄ particles was about 6 nm. The NiS coated Fe₃O₄ particles were tested as positive materials for nickel-iron batteries and found to effectively inhibit the iron anode passivation and improve the efficiency of charge capacity. The NiS (1.5%) – Fe₃O₄ nanoparticles delivered a significant power density of 557.2 mA h g^?1 at a current density of 120 mA g^?1, with a charging efficiency of 79.6%. Furthermore, discharge capacities of 550.2 and 436.8 mA h g^?1 were achieved respectively at 300 and 600 mA g^?1, with charging efficiencies reaching up 85.9% and 76.5% of the initial capacity after 100 cycles.     

Synthesis of carbon coated Fe3O4/SnO2 composite beads and their application as anodes for lithium ion batteries

Abstract

Two metal oxide materials, namely, Fe₃O₄ and SnO₂, were combined into one specially designed nanostructure for lithium ion battery application. Hollow and porous Fe₃O₄ beads with an average size of ～700 nm were first synthesised through a one-step solvothermal route, followed by the decoration of SnO₂ nanoparticles via a hydrothermal method. A thin carbon layer was coated to further enhance the overall electrochemical performances. Under the current density of 100 mA g^?1, the first reversible capacity of such composite beads reached 834·7 mA h g^?1. While being tested at a higher current density of 500 mA g^?1, carbon coated Fe₃O₄/SnO₂ delivered steady reversible capacities with 569·5 mA h g^?1 at two hundredth cycle. Such performances were attributed to the high theoretical capacities of the metal oxides, desired morphology in nanoscale, carbon coating layer and the synergistic effect between Fe₃O₄ and SnO₂.     

In situ fabrication of porous graphene electrodes for high-performance lithiumoxygen batteries

These years, LiO₂ batteries attract wide interest because of its high theoretical energy density. However, the catalytic activity and porous structure of cathode remains a great challenge. In this work, we developed a hierarchical porous graphene foam to serve as a battery cathode, which has much richer active sites for cathodic reaction and channels for Li⁺ transfer and O₂ diffusion. The cathode exhibits a superior specific capacity as high as 9559 mAh g^?1 at 57 mA g^?1 and remains a high-rate capability of 3988 mAh g^?1 at an increased current density of 285 mA g^?1. Benefiting from the well-designed cathode structure, the battery can be stably operated for 150 cycles with a stable voltage profile and voltage efficiency up to 65%. The well-designed graphene has a potential to be a superior free-standing cathode to other carbon-based materials due to its good combination of its hierarchical and porous structure, large surface area, abundant defects and excellent mechanical stability.     

Flower-like architecture of CoSn4 nano structure as anode in lithium ion batteries

CoSn₄ nano-particles were synthesized on Cu and Ni substrates through pulsed current electrodeposition and used as anode in lithium ion batteries. Nano particles with Flower-like morphology were obtained through applying an average current density of 85 mA/cm² on Ni substrate while the particles formed using constant current electrodeposition are greater in size ca. 500 nm. Optimum discharge capacity of synthesized CoSn₄ was obtained 848 mAh g^?1 which reduced to 500 mAh g^?1 at 120th cycle indicating an enhanced electrochemical performance compared to anode films synthesized through other pulsed current densities and also constant current electrodeposition. This high discharge capacity and cycleability is attributed to finer crystal grains and flower-like morphology of nano particles. Also, the sample synthesized on Ni substrate showed higher cycleability and noticeably lower resistance. High resistance of anode film synthesized on Cu substrate is due to the corrosion and passivation of copper occurred by HF formation in LiPF₆ electrolyte.     

One step synthesis of rGO-Ni3S2 nano-cubes composite for high-performance supercapacitor electrodes

In the last decade, supercapacitors possessing high power density and cyclic stability have attracted great interests in various applications. Graphene-based composite electrodes are known as a promising candidate for supercapacitors due to synergistic effects. For the first time, in this work, we develop a simple one-step hydrothermal synthesis of graphene wrapped Ni₃S₂ nanocubes (rGO-Ni₃S₂) composite for high-performance and low-cost supercapacitor electrodes. The rGO-Ni₃S₂ electrode exhibits an ultrahigh specific capacity of 616 C g^?1 at the current density of 1 A g^?1 with excellent cycling durability of 92.7% after 5000 cycles, which is much better when compared with the counterpart without graphene (pure Ni₃S₂). We attribute the remarkable performance of the rGO-Ni₃S₂ electrode to the synergistic effects of the graphene as the conductive support and Ni₃S₂ cubics as the pseudocapacitive material. This work constitutes a step forward towards the development of low-cost and high-performance supercapacitors for the next generation of portable electronics.     

Ion assisted anchoring Sn nanoparticles on nitrogen-doped graphene as an anode for lithium ion batteries

Though lithium ion batteries are popular in many fields, high performance electrode materials with reasonable structure are desired. Herein, Sn/nitrogen-doped graphene (NGN) was fabricated with the help of 7,7,8,8-tetracyanoquinodimethane anion (TCNQ∙^-). TCNQ∙^- was used to anchor Sn⁴⁺ into the graphene layer with the electrostatic interaction, which improves the distribution of Sn nanoparticles. Meanwhile, TCNQ∙^- acts as a nitrogen source to construct N doped graphene, enhancing the electron conductivity of the composite. Benefiting from the strong structure and good ion/electron conductivity, the Sn/NGN composite achieved excellent electrochemical battery performance. At high rates of 1 and 2 A g⁻¹, capacities of 433 and 353 mA h g⁻¹ were acquired, respectively. Moreover, the Sn/NGN composite outputted a high capacity of 584 mA h g⁻¹ at the end of 1000 cycles at 1 A g⁻¹.     

Cooperation of Fe2O3@C and Co3O4/C subunits enhances the cyclic stability of Fe2O3@C/Co3O4 electrodes for lithium‐ion batteries

A Fe₂O₃@C/Co₃O₄ hybrid composite anode is synthesized via a two‐step hydrothermal method in which the acetylene carbon black component serves as a conductive matrix and as an effective elastic buffer to relieve the stress from Fe₂O₃@C and Co₃O₄/C during the electrochemical testing. The crystallinity, structure, morphology, and electrochemical performance of the composites are systematically characterized. Galvanostatic charge/discharge measurements of Fe₂O₃@C/Co₃O₄ present the excellent rate performance and cyclic stability. Its reversible capacity reaches 1478 mAh·g^?1 after 45 cycles, and it is equal to 1035 mAh·g^?1 after 350 cycles at a current density of 200 mA·g^?1. Furthermore, the changes after 30, 45, 60, 90, and 120 cycles are investigated. It is found that the electrochemical performance varies with the morphological change of the electrode surface. Correspondingly, the microstructure, cyclic voltammetry curves, and Nyquist plots significantly change as a consequence of cycling. The results of this study provide an understanding of the increased capacity and excellent cyclic performance of a new anodic material for Li‐ion batteries.     

Synthesis of SnO2 nanorods and hollow spheres and their electrochemical properties as anode materials for lithium ion batteries

Abstract

SnO₂ nanorods and hollow spheres were conducted via a surfactant assisted hydrothermal reaction with the hydrothermal temperature. The crystalline structure and morphologies of the as prepared samples were characterised by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results indicate that the products are hollow spheres with diameters of approximately 400–800 nm and shell thicknesses of 60–70 nm via hydrothermal treating at 160°C for 42 h and rod-like nanostructures with diameters of ～30 nm and lengths of 100–300 nm via hydrothermal treating at 200°C for 42 h respectively. The as prepared samples were used as anode materials for lithium ion battery, whose charge–discharge properties and cycle performance were examined. The results show that the initial discharge capacities of SnO₂ hollow spheres and SnO₂ nanorods samples are 1303 and 1426 mA h g^?1 at 0·2C rate, and still retain charge capacities of 518 and 578 mA h g^?1 respectively. Its good cycling behaviour and charge capacities make it a promising cathode material for advanced electrochemical devices for lithium ion batteries.     

TiF3 catalyzed MgH2 as a Li/Na ion battery anode

MgH₂ has been considered as a potential anode material for Li ion batteries due to its low cost and high theoretical capacity. However, it suffers from low electronic conductivity and slow kinetics for hydrogen sorption at room temperature that results in poor reversibility, cycling stability and rate capability for Li ion storage. This work presents a MgH₂–TiF₃@CNT based Li ion battery anode manufactured via a conventional slurry based method. Working with a liquid electrolyte at room temperature, it achieves a high capacity retention of 543 mAh g^?1 in 70 cycles at 0.2 C and an improved rate capability, thanks to the improved hydrogen sorption kinetics with the presence of catalytic TiF₃. Meanwhile, the first realization of Na ion uptake in MgH₂ has been evidenced in experiments.     

Characteristics of Sn/Li2O multilayer composite anode for thin film microbattery

Sputtering growth of a Sn/Li₂O multilayer composite thin film is conducted to produce an anode thin film with less capacity fading than that of a pure SnO₂ film for a thin-film battery. The structural properties of the Sn/Li₂O multilayer are examined. In addition, the electrochemical characteristics of the Sn/Li₂O and pure SnO₂ thin films are compared. X-ray diffraction and transmission electron microscopy measurements reveal a Sn crystalline peak only and a Sn–Li₂O multilayer structure, respectively, in the Sn/Li₂O thin film. A SnO₂ thin film with a polycrystalline phase shows an irreversible side-reaction at 0.8 V versus Li/Li⁺, an initial charge retention of about 29%, and poor cycleability in the cut-off voltage range from 1.2 to 0 V versus Li/Li⁺. By contrast, no irreversible side-reaction is found in the Sn/Li₂O multilayer composite thin film while there is an initial charge retention of 49% and better cycleability (more than twice) than that of pure SnO₂ film after about 150 cycles. These results indicate that the Sn/Li₂O multilayer composite thin film can be used for tin-based, thin-film, microbatteries and provide motivation to pursue fabrication of Sn–Li₂O anode powder for bulk type batteries.     

Enhanced performance of alpha‐Fe2O3 nanoparticles with optimized graphene coated layer as anodes for lithium‐ion batteries

A series of different α‐Fe₂O₃ nanoparticles composites containing different amounts of graphene coatings have been successfully prepared using a simple electrostatic self‐assembly (ESA) method. The structure and electrochemical properties of these α‐Fe₂O₃@graphene composites have been investigated. The α‐Fe₂O₃ nanoparticles composite containing 40 wt% graphene coating exhibits the highest specific capacity (385 mAh g^?1) under 1000 mA g^?1, resulting in superior cycle stability with no downward trend after 500 cycles. These results demonstrate that graphene coatings can be used to enhance the electrochemical properties and morphological stability of α‐Fe₂O₃ nanoparticles as anodic materials for high performance lithium‐ion batteries (LIBs). The low‐energy self‐assembly method employed in the paper has good potential for the broad‐scale preparation of other graphene‐modified materials because of its simplicity and the relatively low temperature conditions.     

Electrochemical performance of Li4Ti5O12/carbon nanotubes/graphene composite as an anode material in lithium-ion batteries

A three-dimensional Li₄Ti₅O₁₂/carbon nanotubes/graphene composite (LTO-CNT-G) was prepared by ball-milling method, followed by microwave heating. The as-prepared LTO-CNT-G composite as anode material in lithium-ion battery exhibited superior rate capability and cycle performance under relative high current density compared with that of Li₄Ti₅O₁₂/CNTs (LTO-CNT) and Li₄Ti₅O₁₂/graphene (LTO-G) composites. Graphene nanosheets and CNTs were used to construct 3D conducting networks, leading to faster electron transfer and lower resistance during the lithium ion reversible reaction, which significantly enhanced the electrochemical activity of LTO-CNT-G composite. The synergistic effect of graphene and CNTs can greatly improve the rate capability and cycling stability of Li₄Ti₅O₁₂-based anodes. The LTO-CNT-G composite exhibited a high initial discharge capacity of 172 mAh g^?1 at 0.2 C and 132 mAh g^?1 at 20 C, as well as an excellent cycling stability. The electrochemical impedance spectroscopy demonstrated that the LTO-CNT-G composite has the smallest charge-transfer resistance compared with the LTO-CNT and LTO-G composites, indicating that the fast electron transfer from the electrolyte to the LTO-CNT-G active materials during the lithium ion intercalation/deintercalation owing to the three-dimensional networks of graphene and CNTs.     

One step electrodeposition of V2O5/polypyrrole/graphene oxide ternary nanocomposite for preparation of a high performance supercapacitor

A new ternary nanocomposite based on graphene oxide (GO), polypyrrole (PPy) and vanadium pentoxide (V₂O₅) is obtained via one-step electrochemical deposition process. Electrochemical deposition of V₂O₅, PPy and GO on a stainless steel (SS) substrate is conducted from an aqueous solution containing vanadyl acetate, pyrrole and GO to get V₂O₅/PPy/GO nanocomposite. Characterization of the electrode material is carried out by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). The electrochemical performance of the as-prepared nanocomposite is evaluated by different electrochemical methods including cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS) in 0.5 M Na₂SO₄ solution. Remarkably, V₂O₅/PPy/GO nanocomposite shows a specific capacitance of 750 F g^?1 at a current density of 5 A g^?1, which is far better than PPy (59.5 F g^?1), V₂O₅/PPy (81.5 F g^?1) and PPy/GO (344.5 F g^?1). Furthermore, V₂O₅/PPy/GO maintains 83% of its initial value after 3000 cycles, which demonstrates good electrochemical stability of the electrode during repeated cycling. These results demonstrate that the combination of electrical double layer capacitance of GO and pseudocapacitive behavior of the PPy and V₂O₅ can effectively increase the specific capacitance and cycling stability of the prepared electrode. Also, a symmetric supercapacitor device assembled by V₂O₅/PPy/GO nanocomposite yielded a maximum energy density of 27.6 W h kg^?1 at a power density of 3600 W kg^?1, and a maximum power density of 13680 W kg^?1 at an energy density of 22.8 W h kg^?1.