Xianhua Hou

Facile synthesis of ZnFe2O4 with inflorescence spicate architecture as anode materials for lithium-ion batteries with outstanding performance

ZnFe2O4 with inflorescence spicate architecture has been synthesized by a facile co-precipitation method with the presence of oxalic acid. The ZnFe2O4 as an anode material with novel morphological structure was emphasized by X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), Raman spectroscopy and so on. As an anode for LIBs, the inflorescence spicate ZnFe2O4 exhibits excellent electrochemical performance with an initial discharge capacity of 1647.2 mA h g−1, maintaining a reversible discharge capacity of 1398.1 mA h g−1 after 100 cycles at a current density of 100 mA g−1 (84.9% of the first discharge capacity) and favorable rate capacity (766 mA h g−1 at 1.2 A g−1). Such attractive performance is ascribed mainly to its unique inflorescence spicate electrode morphology, which can provide good electrical contact and conductivity, and provide a buffer medium to accommodate the volume expansion of electrode materials during the electrochemical reaction process. More importantly, this study not only provides a simple synthesis method for lithium-ion batteries, but also helps in designing novel electrode materials with high performance.

Corncob-shaped ZnFe2O4/C nanostructures for improved anode rate and cycle performance in lithium-ion batteries

Novel corncob-shaped ZnFe2O4/C nanostructured composite materials have been successfully synthesized through a facile co-precipitation method with carbamide as carbonaceous matrix. The morphology and structure of the samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and transition electron microscopy (TEM), and the physical and electrochemical properties were tested by thermogravimetry and an electrochemical system. The corncob-shaped ZnFe2O4/C nanostructured anode materials exhibit outstanding cycling performance and rate capability in comparison with pure ZnFe2O4 anode materials. Electrochemical results show that the corncob-shaped ZnFe2O4/C nanocomposite materials exhibit an initial discharge capacity of approximately 1591.6 mA h g−1 with an initial coulombic efficiency of 80.4% at a constant density of 100 mA g−1. A reversible discharge capacity of 1119.1 mA h g−1 is still obtained after 100 cycles. The discharge capacities can still be as high as 889 mA h g−1 at a high rate of 4 C (1 C = 250 mA g−1). The excellent electrochemical performances are probably ascribed to the multiple synergetic factors that stem from their uniform nanoparticle size, complete crystallization with corncob shape, and organic pyrolysis of carbon inlaid in the corncob shaped nanostructure. The corncob-shaped ZnFe2O4/C nanocomposite will be a promising anode material for advanced lithium ion batteries.

Template GNL-assisted Synthesis of Porous Li1.2Mn0.534Ni0.133Co0.133O2: Towards High Performance Cathodes for Lithium Ion Batteries

Modified porous spherical Li1.2Mn0.534Ni0.133Co0.133O2 has been successfully synthesized via a co-precipitation method, adopting graphene and carbon nanotube conductive liquid (GNL) as a template and surface modified material. The unique porous structure and the larger specific surface area of the porous Li1.2Mn0.534Ni0.133Co0.133O2 contribute to both the increase in the first coulombic efficiency, from 76.3% to 82.0%, and the enhancement of the rate capability, demonstrating initial discharge capacities of 276.2, 245.8, 218.8, 203.9, 178.8, 135.9 and 97.5 mA h g−1 at different discharge rates of 0.1, 0.2, 0.5, 1.0, 2.0, 5.0 and 10 C, respectively. Even after suffering 100 cycles of charge–discharge, the porous Li-rich cathode can still deliver a discharge capacity of 235.5 mA h g−1, suggesting a high capacity retention of 86.2% compared to the initial discharge capacity (273.3 mA h g−1). Besides, the diffusion coefficient of the Li+ investigated by the cyclic voltammetry technique is approximately 10−12 cm2 s−1, indicating faster kinetics of the lithium ions for the modified porous Li1.2Mn0.534Ni0.133Co0.133O2 compared with the ordinary Li1.2Mn0.534Ni0.133Co0.133O2 (∼10−13 cm2 s−1). In fact, the introduction of GNL as a template not only leads to the porous structure of the Li-rich cathode material but also brings about improvement to the crystallinity and size of the grains, which can be ascribed to the combined effect of the GNL with the carbonate precursors of MCO3 (M = Mn, Ni, Co) during the recrystallization process.

Facile spray-drying/pyrolysis synthesis of intertwined SiO@CNFs&G composites as superior anode materials for Li-ion batteries

A silicon monoxide/carbon nanofibers/graphite (SiO@CNFsG carbon nanofibers intertwined with carbon coated silicon monoxide spherical composites and embedded micron-sized graphite. The combination of twisted carbon nanofibers, graphite and amorphous carbon-coating layer accommodates the large volume change of silicon during the lithium intercalation/extraction process, which stabilizes electrode structure during discharge–charge cycles. As an anode material, the as-obtained SiO@CNFs&G composite demonstrates high capacity and excellent cycle stability. An initial specific discharge capacity of approximately 1031.7 mA h g−1 with a coulombic efficiency of 56.6% and a reversible specific capacity of approximately 615.1 mA h g−1 after 100 cycles at a constant density of 100 mA g−1 is achieved, which is about two times the values for graphite. Because of the facile synthesis process and fascinating performance of the prepared electrode, significant commercial potential is expected.

The design and synthesis of porous NiCo2O4 ellipsoids supported by flexile carbon nanotubes with enhanced lithium-storage properties for lithium-ion batteries

Porous NiCo2O4 ellipsoids supported by flexile carbon nanotubes (denoted as NCO/CNTs) were successfully synthesized by a facile hydrothermal method followed by subsequent annealing in air. The structure and morphology of the materials were characterized by X-ray diffraction, field-emission scanning electron microscopy, and transmission electron microscopy. When evaluated as anode materials for lithium-ion batteries (LIBs), the NCO/CNTs composites exhibit a high and stable reversible capacity (1273.8 mA h g−1 at 500 mA g−1), excellent rate capability (593.0 mA h g−1 at 4000 mA g−1), and long cycling stability (no capacity fade over 200 cycles). The improved performance of these LIBs can be attributed to the unique 3D porous NCO/CNTs composite frameworks, which will enhance electrical conductivity of the materials, facilitate fast ion/electron transport through the electrode, and accommodate massive volume expansion/contraction during cycling. Furthermore, the synthetic strategy is simple but very effective, it can be easily extended to prepare many other metal oxides with the CNTs acting as the conductive network and used as promising anode materials for high-performance LIBs.

3-Aminopropyltriethoxysilane-Assisted Si@SiO2/CNTs Hybrid Microspheres as Superior Anode Materials for Li-ion Batteries

A silicon based composite (Si@SiO2/CNTs) with outstanding electrochemistry performance has been easily synthesized using a spray drying method; The composite microsphere is mainly made up of carbon nanotubes and the prepared nano silicon particles. With the help of a silane coupling agent, carbon nanotubes tightly intertwined with nano silicon particles and formed microspheres together. On the surface of the prepared nano silicon particles, a layer of oxide film plays a role as a barrier to reduce the rupture of the particles during the lithium intercalation/extraction process. In addition, the added twisted carbon nanotubes can help to maintain the conductive network, thus stabilizing the electrode working environment during the lithium intercalation/extraction process. As a superior anode material, an initial specific discharge capacity of approximately 2846.9 mAh g−1 with a coulombic efficiency of 86 % and a reversible specific capacity of 2035.9 mAh g−1 after 100 cycles at a constant density of 500 mA g−1 are obtained.

Facile synthesis of hierarchical CoMn 2 O 4 microspheres with porous and micro-/nanostructural morphology as anode electrodes for lithium-ion batteries

AbstractHierarchical CoMn2O4 microspheres assembled by nanoparticles have been successfully synthesized by a facile hydrothermal method and a subsequent annealing treatment. XRD detection indicate the crystal structure. SEM and TEM results reveal the 3-dimensional porous and micro-/nanostructural microsphere assembled by nanoparticles with a size of 20-100 nm. The CoMn2O4 electrode show initial specific discharge capacity of approximately 1546 mAh/g at the current rates 100 mA/g with a coulombic efficiency of 66.7% and remarkable specific capacities (1029-485 mAh/g) at various current rates (100-2800 mA/g).

Chemically integrated hierarchical hybrid zinc cobaltate/reduced graphene oxide microspheres as an enhanced lithium-ion battery anode

Chemically integrated hierarchical microsphere ZnCo2O4/reduced graphene oxide hybrid composites are synthesized via a polyol process. Microsphere ZnCo2O4 particles embedded in graphene homogeneously with sizes in the region of 320–512 nm, graphene sheets grew and interwove inversely in the inside of the microsphere ZnCo2O4 particles, so that the structure possesses a unique microsphere–sheet hybrid structure. The interconnected graphene conductive network basic skeleton is beneficial to the transportation of Li+ and electrons. Compared with the conventional way metal oxides and graphene combine, hierarchical microsphere ZnCo2O4/reduced graphene oxide hybrid composites exhibit enhanced rate capability (469.7 mA h g−1 at 4000 mA g−1) and long term cycling ability with high capability (904.2 mA h g−1 at 1000 mA g−1 over 500 charge/discharge cycles), owing to the special characteristic of a three-dimensional structure. Most importantly, with the successful synthesis of the hierarchical microsphere ZnCo2O4/reduced graphene oxide hybrid composites, this facile strategy can extend to the synthesis of the ternary transition metal oxides/reduced graphene oxide with hierarchical microsphere structure and make it possible to explore a more promising storage application.

3-Dimensional cuboid structured ZnFe2O4@C nano-whiskers as anode materials for lithium-ion batteries based on the in situ graft polymerization method

3-Dimensional cuboid structured ZnFe2O4@C nano-whiskers anode materials have been successfully synthesized via an in situ graft copolymerization method and the subsequent calcination process. Polystyrene-acrylonitrile (PSA) serves as the coating layer, which plays an important role in the calcination process. The final electrode materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results of electrochemical tests demonstrate an excellent electrochemical performance, including good rate capability (over 700 mA h g−1 at the current density of 3.2 A g−1) and good cycling performance (a reversible capacity of 1722 mA h g−1 after 120 cycles with coulombic efficiency of 98.4%). Therefore, we believe that the proposed work may be a potential method to assist ZnFe2O4 to be a quite promising alternative anode material for lithium-ion batteries (LIBs).

Electronic, magnetic, catalytic, and electrochemical properties of two-dimensional Janus transition metal chalcogenides

Two dimensional (2D) nanomaterials have received increasing interest because of their unique properties for versatile applications. In this work, we present a first-principles study on a new family of 2D nanostructures, Janus transition metal chalcogenide MSX (M = Ti or V; and X = C, N, Si, or P) monolayers, for their multifunctional applications. In this work, we show that the Janus MSXs possess diverse electronic and magnetic properties, and can be semiconducting or metallic, and nonmagnetic or magnetic, depending on their composition. We find that a TiSC monolayer with a 1H phase (TiSC-1H) is suitable as a cathode for Li ion batteries and anode materials for Na and Mg ion batteries due to its high open circuit voltage (OCV) (2.121 eV) for Li, and low OCVs upon Na (0.676 eV) and Mg (1.044 eV) intercalation, respectively. Importantly, TiSC-1H shows fast charge/discharge rates, good cycling stability, and high storage density as electrode materials for rechargeable batteries because of low ion diffusion barriers, small volume expansion and high specific capacity. We further show that TiSP-1H has the best performance in the hydrogen evolution reaction due to both its catalytic activities on the surfaces and relatively low overpotentials upon hydrogenation. Our study demonstrates that the 2D Janus MSXs may find multifunctional applications in nanodevices, spintronics, catalysis, and electrochemical energy storage.