3D composites of ZnSnO<Subscript>3</Subscript> nanoplates/reduced graphene oxide aerogels as an advanced lithium-ion battery anode

Zinc-based bimetal oxides have received considerable attention as anode for lithium-ion batteries (LIBs). A one-pot self-assembly hydrothermal method is developed for the fabrication of 3D hierarchical structure aerogels from zinc stannate (ZnSnO₃) and reduced graphene oxide (rGO). 3D interconnected porous structure with ZnSnO₃ hexagon nanoplates uniformly dispersed on graphene sheets has been constructed successfully, in which the crystalline hexagon nanoplates ZnSnO₃ are firstly used to prepare ZnSnO₃-based anode materials for LIBs. The as-prepared ZnSnO₃ nanoplates/reduced graphene oxide aerogels (ZnSnO₃–rGAs) electrode demonstrates an excellent reversible capacity (780 mAh g^?1) after 200 cycles at a certain current density (100 mA g^?1) and still delivers a specific capacity of 460 mAh g^?1 even at 1000 mA g^?1. The superior performance of lithium storage is attributed to the 3D porous hierarchical structure and the synergistic effects of uniform hexagon nanoplates ZnSnO₃ and rGO sheets.     

Ordered mesoporous carbon-supported CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> composite with enhanced lithium storage properties

A high and stable reversible specific capacity (1277.7 mAh g^?1) was successfully achieved by the CoFe₂O₄/ordered mesoporous carbon nanohybrids (CFO/CMK-3) composite anode at the current density of 0.1 A g^?1 after 100 cycles. CFO/CMK-3 electrode also exhibited a stable capacity up to 733.2 and 482.6 mAh g^?1 at the current densities of 0.5 and 1 A g^?1 after 500 cycles, respectively. The CFO particles were found to be uniformly distributed inside the pore channels of CMK-3. Structure characterization before and after 100 tests revealed that the specific CMK-3 mesoporous structure and CFO crystallites remained unchanged. The stability of the anode composite stability and the rapid redox capability of CFO gave rise to superior lithium storage capacity and excellent cycling stability. CFO/CMK-3 showed a great promise to serve as anode for high-performance lithium-ion battery.     

Mn<Subscript>3</Subscript>O<Subscript>4</Subscript> nanorods with secondary plate-like nanostructures; preparation,characterization and application as high performance electrode material in supercapacitors

Mn₃O₄ nanorods with secondary plate-like structures were prepared through precipitation from a 0.005 M manganese chloride bath, under the applying direct current mode (i = 2 mA cm^?2). The structural analysis through XRD and FTIR confirmed that the deposited nanopowder has pure monoclinic phase of Mn₃O₄. Further morphological assessment through SEM proved the product to have the Mn₃O₄ nanorods in large quantity, which constructed the secondary plate-like building blocks. Cyclic voltammetric and charge–discharge experiments on the product indicated the prepared Mn₃O₄ to possess high specific capacitance (SC) values of 298 F g^?1, as well as an outstandingly durable cycling stability (95.1 % of initial capacity after discharging 1000 cycles).     

Preparation and electrochemical properties of nanorods and nanosheets structural Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> as anode for lithium ion batteries

In this study, nanorods and nanosheets structure of Li₄Ti₅O₁₂ (LTO) with higher capacity and cycle performance are prepared by hydrothermal synthesis. We can obtain different nanostructural LTO by changing heating time in autoclave and molar ratio between lithium (Li) and titanium (Ti). Precursor was calcined at 600 °C for 6 h in air after heating to 180 °C with the holding time of 12 and 24 h in Teflon-lined PTFE autoclave vessel, nanorods and nanosheets structure of LTO were prepared successfully, respectively. Specially, when the molar ratio between Li and Ti was 4.2:5, the discharge capacities were 177.7 and 230.7 mAh g^?1 at 20 mA g^?1, respectively. When the holding time was 24 h as well as molar ratio between Li and Ti was 4.2:5, the band gap was least, and this pure LTO reversible capacities reached 90.36 and 73.12% after 200 and 3000 cycles at 100 mA g^?1 and 1 A g^?1, respectively.     

Cr<Subscript>2</Subscript>O<Subscript>3</Subscript> nanocrystal anode materials with improved cyclic stability for lithium ion batteries

The cyclic stability of Cr₂O₃ is very poor due to the large volume change during lithiation/delithiation. In this study, we have found that Cr₂O₃ nanocrystals synthesized by using a simple hydrothermal method can improve its cyclic stability. Sample calcined at 430 °C has uniform size, compact structure and high crystallization degree. These Cr₂O₃ nanocrystals exhibit a stable cyclic performance of 185 mAh g^?1 after 100 cycles at 100 mA g^?1. It is useful in real life, such as providing power consumption for minitype device, etc.     

Ionic liquid-derived Co<Subscript>3</Subscript>O<Subscript>4</Subscript>/carbon nano-onions composite and its enhanced performance as anode for lithium-ion batteries

In this work, a novel composite of Co₃O₄ nanoparticle and carbon nano-onions (CNOs) is synthesized by using ionic liquid as carbon and nitrogen source through a facile carbothermic reduction followed by low-temperature oxidation method. The SEM and HRTEM images reveal that the Co₃O₄ particles are homogenously embedded in the CNOs. Due to the unique nano-structure, the electrolyte contacts well with the active materials, leading to a better transfer of lithium ions. Moreover, the unique nano-structure not only buffers the volume changes but also facilitates the shuttling of electrons during the cycling process. As a result, the electrode made up of Co₃O₄/CNOs composite delivers favorable cycling performance (676 mAh g^?1 after 200 cycles) and rate capability (557 mAh g^?1 at the current of 1 C), showing a promising prospect for lithium-ion batteries as anode materials.     

Light weight RGO/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanocomposite for efficient electromagnetic absorption coating in X-band

Reduced graphene oxide (RGO)/magnetite (Fe₃O₄) nanocomposite has been synthesized by an in-situ facile hydrothermal method. The XRD pattern reveals the development of nanocomposite in which both phases are coexistent. Raman Spectroscopy shows the main characteristics peaks of D and G bands at 1349 cm^?1 and 1595 cm^?1 for graphitic structures. The intensity ratio (I_D/I_G) is also calculated, which indicate the degree of defects in the material. This ratio (I_D/I_G), increases from 0.84 for GO to 0.91 for RGO/Fe₃O₄ nanocomposite and promotes the defects which are beneficial for electromagnetic (EM) absorption. The SEM image depicts that, Fe₃O₄ spherical nanoparticles are dispersed over the surface of graphene sheets and provide a thermal conducting path for heat dissipation between different layers of graphene. The EM absorption properties have been analyzed at 2–18 GHz of RGO and RGO/Fe₃O₄. The addition of proper content of Fe₃O₄ magnetic nanoparticles in RGO sheets improved the Reflection Loss (RL) from ??13.5 dB to ??20 dB at a frequency of 9.5 GHz. Moreover, due to magnetic loss and interfacial polarization, the effective bandwidth increases from 2.5 GHz to 3.8 GHz at a coating thickness of 1.5 mm. Hence this light weight nanocomposite is an excellent material for strong EM absorption in X-band.     

Template-free synthesis of Ni<Subscript>2</Subscript>P hollow microspheres with great photocatalytic and electrochemical properties

The hollow Ni₂P microspheres were prepared using a facile one-step template-free solvothermal method. The products were characterized and the results showed that they were pure hexagonal Ni₂P microspheres, made up of large amounts of Ni₂P nanoparticles, and had an obvious inner space in the central of the microspheres. After being investigated, it was found that these Ni₂P hollow spheres initially were some solid spheres, but after a specified time, they were converted to a hollow structure by an Ostwald ripening process, some even had a multi-wall hollow structure. Meanwhile, the as-prepared Ni₂P hollow spheres showed a good photocatalytic degradation performance for Methylene Blue in aqueous solution. Electrochemical measurements turned out that the Ni₂P hollow spheres have a great cycling performance. The initial discharge capacity capacity of is Ni₂P hollow spheres up to 660 mAh g^?1 and it always keep in about 300 mAh g^?1 within 100 cycles at the current density of 100 mA g^?1.     

Construction of point-line-plane (0-1-2 dimensional) Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-SnO<Subscript>2</Subscript>/graphene hybrids as the anodes with excellent lithium storage capability

The assembly of hybrid nanomaterials has opened up a new direction for the construction of high-performance anodes for lithium-ion batteries (LIBs). In this work, we present a straightforward, eco-friendly, one-step hydrothermal protocol for the synthesis of a new type of Fe₂O₃-SnO₂/graphene hybrid, in which zero-dimensional (0D) SnO₂ nanoparticles with an average diameter of 8 nm and one-dimensional (1D) Fe₂O₃ nanorods with a length of ~150 nm are homogeneously attached onto two-dimensional (2D) reduced graphene oxide nanosheets, generating a unique point-line-plane (0D-1D-2D) architecture. The achieved Fe₂O₃-SnO₂/graphene exhibits a well-defined morphology, a uniform size, and good monodispersity. As anode materials for LIBs, the hybrids exhibit a remarkable reversible capacity of 1,530 mA·g^?1 at a current density of 100 mA·g^?1 after 200 cycles, as well as a high rate capability of 615 mAh·g^?1 at 2,000 mA·g^?1. Detailed characterizations reveal that the superior lithium-storage capacity and good cycle stability of the hybrids arise from their peculiar hybrid nanostructure and conductive graphene matrix, as well as the synergistic interaction among the components.

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Samarium-doped Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles with improved magnetic and supercapacitive performance: a novel preparation strategy and characterization

Sm³⁺-doped magnetite (Fe₃O₄) nanoparticles were synthesized through a one-pot facile electrochemical method. In this method, products were electrodeposited on a stainless steel (316L) cathode from an additive-free 0.005 M Fe(NO₃)₃/FeCl₂/SmCl₃ aqueous electrolyte. The structural characterizations through X-ray diffraction, field-emission electron microscopy, and energy-dispersive X-ray indicated that the deposited material has Sm³⁺-doped magnetite particles with average size of 20 nm. Magnetic analysis by VSM revealed the superparamagnetic nature of the prepared nanoparticles (Ms = 41.89 emu g^?1, Mr = 0.12 emu g^?1, and H _Ci = 2.24 G). The supercapacitive capability evaluation of the prepared magnetite nanoparticles through cyclic voltammetry and galvanostat charge–discharge showed that these materials are capable to deliver specific capacitances as high as 207 F g^?1 (at 0.5 A g^?1) and 145 F g^?1 (at 2 A g^?1), and capacity retentions of 94.5 and 84.6% after 2000 cycling at 0.5 and 1 A g^?1, respectively. The results proved the suitability of the electrosynthesized nanoparticles for use in supercapacitors. Furthermore, this work provides a facile electrochemical route for the synthesis of lanthanide-doped magnetite nanoparticles.     

Electrochemical performance and thermal stability of GaF3-coated LiNi0.5Mn1.5O4 as 5 V cathode materials for lithium ion batteries

LiNi_0.5Mn_1.5O₄ coated with various amounts of GaF₃ were prepared and investigated as cathode materials for lithium ion batteries. The sample was characterized by X-ray diffraction, transmission electron microscopy, and energy-dispersive X-ray spectroscopy (EDX). The results indicated that the electrochemical performance of LiNi_0.5Mn_1.5O₄ was effectively improved by the GaF₃ coating. The 0.5 wt% GaF₃-coated LiNi_0.5Mn_1.5O₄ delivered a discharge capacity of 97 mAh g^?1 at 20 C (3000 mA g^?1), while the pristine sample only yielded 80 mAh g^?1 at 10 C. Meanwhile, the 0.5 wt% GaF₃-coated LiNi_0.5Mn_1.5O₄ exhibited an obviously better cycle life than the bare sample at 60 °C, delivering a discharge capacity of 120.4 mAh g^?1 after 300 cycles, 82.9 % of its initial discharge capacity, while the pristine only gave 75 mAh g^?1. At 0.1 C, the self-discharge of 0.5 wt% GaF₃-coated LiNi_0.5Mn_1.5O₄ is about 3.4 %, while the pristine is about 10.2 % after a 5-day rest at room temperature. Furthermore, GaF₃ coating greatly reduced the self-heating rate and improved the thermal stability of LiNi_0.5Mn_1.5O₄. These improvements were attributed to the GaF₃ layer not only increasing the electronic conductivity of the LiNi_0.5Mn_1.5O₄ but also effectively suppressing the reaction between the LiNi_0.5Mn_1.5O₄ and the electrolytes, which reduced the charge-transfer impedance and the dissolution of Ni and Mn during cycling.     

Graphene oxide-decorated Fe<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript> microflowers as a promising anode for lithium and sodium storage

Mixed transition metal oxides (MTMOs) have received intensive attention as promising anode materials for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). In this work, we demonstrate a facile one-step water-bath method for the preparation of graphene oxide (GO) decorated Fe₂(MoO₄)₃ (FMO) microflower composite (FMO/GO), in which the FMO is constructed by numerous nanosheets. The resulting FMO/GO exhibits excellent electrochemical performances in both LIBs and SIBs. As the anode material for LIBs, the FMO/GO delivers a high capacity of 1,220 mAh·g^–1 at 200 mA·g^–1 after 50 cycles and a capacity of 685 mAh·g^–1 at a high current density of 10 A·g^–1. As the anode material for SIBs, the FMO/GO shows an initial discharge capacity of 571 mAh·g^–1 at 100 mA·g^–1, maintaining a discharge capacity of 307 mAh·g^–1 after 100 cycles. The promising performance is attributed to the good electrical transport from the intimate contact between FMO and graphene oxide. This work indicates that the FMO/GO composite is a promising anode for high-performance lithium and sodium storage.

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Impact of CTAB on morphology and electrochemical performance of MoS<Subscript>2</Subscript> nanoflowers with improved lithium storage properties

The search for high capacity, low-cost electrode materials for lithium-ion batteries is a significant challenge in energy research. Among the numerous potential candidates, layered compounds such as MoS₂ (Molybdenum Disulfide) have attracted increasing attention. A facile hydrothermal reduction process using hexadecyltrimethy ammonium bromide (CTAB) as surfactant was developed for the synthesis of lithium-ion battery anode material MoS₂ nanoflowers. The impact of CTAB on morphology and electrochemical performance of MoS₂ has been investigated. With the increase of CTAB content, MoS₂ ultrathin nanosheets with high specific surface area and more active sites have been successfully synthesized. Electrochemical measurements demonstrated that MoS₂ nanoflowers synthesized with 1% content of CTAB have better electrochemical performance than others as anode materials for Li-ion batteries, which yield a high discharge capacity of 1245 mAh g^?1 at a current density of 50 mA g^?1 and a stable capacity retention of 740 mAh g^?1 until 100 electrochemical cycles.     

Scalable synthesis of TiO<Subscript>2</Subscript> crystallites embedded in bread-derived carbon matrix with enhanced lithium storage performance

TiO₂/carbon (C/TiO₂) composites have been synthesized via an in-situ pyrolysis method using bread as carbon source and investigated as anodes for lithium-ion batteries. As a cheap and common staple food with a sponge-like structure, bread contains a certain amount of moisture, enabling the hydrolysis of tetrabutyl orthotitanate. It is characterized that TiO₂ nanocrystallites are embedded in bread-derived carbon matrix, and their synergetic effect on improving electrochemical properties is demonstrated as well. Partially surface lithium storage of ultrasmall TiO₂ particles is credited to the unique embedment structure. Meanwhile, the carbon species are of importance in enhancing reversible capacities and accelerating interfacial charge transfer. It delivers a reversible capacity of 231 mAh g^?1 at a specific current of 100 mA g^?1 after 200 cycles for the resultant C/TiO₂ composite with 38.8 wt.% carbon. This work presents a facile strategy toward scalable and eco-friendly preparation of metal oxides compositing with carbonaceous materials.     

Enhanced electrochemical reduction of hydrogen peroxide by Co<Subscript>3</Subscript>O<Subscript>4</Subscript> nanowire electrode

Crystalline Co₃O₄ nanowire arrays with different morphologies grown on Ni foam were investigated by varying the reaction temperature, the concentration of precursors, and reaction time. The Co₃O₄ nanowires synthesized under typical reaction condition had a diameter range of approximately 500–900 nm with a length of 17 µm. Electrochemical reduction of hydrogen peroxide (H₂O₂) of the optimized Co₃O₄ nanowire electrode was studied by cyclic voltammetry. A high current density of 101.8 mA cm^?2 was obtained at ?0.4 V in a solution of 0.4 M H₂O₂ and 3.0 M NaOH at room temperature compared to 85.8 mA cm^?2 at ?0.35 V of the Co₃O₄ nanoparticle electrode. Results clearly indicated that the Ni foam supported Co₃O₄ nanowire electrode exhibited superior catalytic activity and mass transport kinetics for H₂O₂ electrochemical reduction.     

Synthesis and microwave absorption properties of sandwich-type CNTs/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/RGO composite with Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> as a bridge

A novel sandwich-type CNTs/Fe₃O₄/RGO composite with Fe₃O₄ as a bridge was successfully prepared through a simple solvent-thermal and ultrasonic method. The structure and morphology of the composite have been characterized by Fourier-transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. This new structure can effectively prevent the agglomeration of GO and the combination of CNTs/Fe₃O₄ and RGO shows a strong reflection loss (R_L) (?50 dB) at 8.7 GHz with absorber thickness of 2.5 mm. Moreover, compared with CNTs/Fe₃O₄/GO composite, it is found that the thermal treating process is beneficial to enhance the microwave absorption properties, which may be attributed to high conductivity of RGO. On this basis, the microwave absorbing mechanism is systematically discussed. All the data show that the CNTs/Fe₃O₄/RGO composite exhibits excellent microwave absorption properties with light density and is expected to have potential applications in microwave absorption.     

Synthesis of Li<Subscript>1.2</Subscript>Mn<Subscript>0.54</Subscript>Co<Subscript>0.13</Subscript>Ni<Subscript>0.13</Subscript>O<Subscript>2</Subscript> by sol–gel method and its electrochemical properties as cathode materials for lithium-ion batteries

Li_1.2Mn_0.54Co_0.13Ni_0.13O₂ was synthesized by sol–gel method at 700, 800, 900 and 1000 °C, respectively, characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and measured as the cathode materials for lithium-ion batteries (LIBs). After their performances have been compared, 800 °C was considered as the optimum synthesis temperature for Li_1.2Mn_0.54Co_0.13Ni_0.13O₂ as the cathode materials for LIBs. When charge–discharged at 20 mA g^?1 in a voltage window of 2.0–4.8 V, the Li_1.2Mn_0.54Co_0.13Ni_0.13O₂ synthesized at 800 °C (LMNCO-800) showed charge and discharge capacities of 376.2 and 276.3 mAh g^?1, respectively, with irreversible capacity of 99.9 mAh g^?1 and Coulombic efficiency of 73.4%, in the first charge–discharge cycle. The discharge capacity was 239.0 mAh g^?1 in the 50th charge–discharge cycle, with capacity retention of 86.6%. The LMNCO-800 also showed superior high-rate performances. When cycled at the rates of 0.5, 1, 2 and 5 C rate (1 C?=?200 mA g^?1), the discharge capacities of the Li_1.2Mn_0.54Co_0.13Ni_0.13O₂ can reach 241, 171, 150 and 110 mAh g^?1, respectively. When characterized with high-resolution transmission electron microscopy (TEM), nanodomains with two different structures can be found in LMNCO-800, with some nanodomains showing monoclinic Li₂MnO₃ structure and the other nanodomains showing hexagonal LiMO₂ structure.     

Self-templated formation of tremella-like MoS<Subscript>2</Subscript> with expanded spacing of (002) crystal planes for Li-ion batteries

Tremella-like MoS₂ consisting of ultrathin nanosheets (~7 nm in thickness) is prepared via a one-pot hydrothermal reaction without using any surfactants and templates. The reaction involves transforming precursor MoO₃ to polyhedral intermediate (K₂NaMoO₃F₃ and K₃Mo₂O₄F₅) through its reaction with Na⁺, K⁺, and F^? ions in the initial stage of hydrothermal reaction. Then the polyhedral intermediate acting as the sacrifice template reacts with the S^2? released from a hydrolysis process of SCN^? ion and transforms to tremella-like MoS₂. The obtained MoS₂ product exhibits expended spacing of the (002) crystal plane, which can facilitate faster lithium ions intercalation behavior. This tremella-like MoS₂ used as an anode material for lithium-ion batteries shows a very high reversible capacity of 693 mA h g^?1 after 50 cycles, good rate capability, and high cyclic capacity retention. Even cycled at a high current density of 4800 mA g^?1, the tremella-like MoS₂ still can deliver a high capacity of 252 mA h g^?1. The secondary hierarchical microstructures consisting of ultrathin nanosheets are beneficial to greatly improved electrochemical performance of the MoS₂ electrode.     

Mn<Subscript>3</Subscript>O<Subscript>4</Subscript>/worm-like mesoporous carbon synthesized via a microwave method for supercapacitors

A quick and facile microwave method has been employed to prepare Mn₃O₄/worm-like mesoporous carbon (Mn₃O₄–MC) composites. Structural and morphological characterizations of worm-like mesoporous carbon and Mn₃O₄–MC composites have been carried out using X-ray diffraction, transmission electron microscopy, N₂ adsorption–desorption, and electrochemical measurement. Cyclic voltammograms demonstrate that the Mn₃O₄–MC composites perform improved capacitive behavior at the range of −0.8~0.2 V (vs. Hg/HgO electrode) with reversibility. The Mn₃O₄–MC composite electrode possesses an enhanced specific capacitance of 266 F g⁻¹ at a sweep rate of 1 mV s⁻¹.     

Enhanced electrochemical performance of Na<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>F<Subscript>3</Subscript> for Na-ion batteries with nanostructure and carbon coating

Carbon-coating Na₃V₂(PO₄)₂F₃ nanoparticles (NVPF@C NP) were prepared by a hydrothermal assisted sol–gel method and applied as cathode materials for Na-ion batteries. The as-prepared nanocomposites were composed of Na₃V₂(PO₄)₂F₃ nanoparticles with a typical size of ~?100 nm and an amorphous carbon layer with the thickness of ~?5 nm. Cyclic voltammetry, rate and cycling, and electrochemical impedance spectroscopy tests were used to discuss the effect of carbon coating and nanostructure. Results display that the as-prepared NVPF@C NP demonstrates a higher rate capability and better long cycling performance compared with bare Na₃V₂(PO₄)₂F₃ bulk (72 mA h g^?1 at 10 C vs 39 mA h g^?1 at 10 and 1 C capacity retention of 95% vs 88% after 50 cycles). The remarking electrode performance was attributed to the combination of nanostructure and carbon coating, which can provide short Na-ion diffusion distance and rapid electron migration.