Qiang Ru

Pineapple-shaped ZnCo2O4 microspheres as anode materials for lithium ion batteries with prominent rate performance

Pineapple-shaped ZnCo2O4 (ZCO) microspheres with a porous nanostructure are synthesized by a typical hydrothermal method and used as high performance anodes in Li-ion batteries. The microspheres show excellent cycling and rate performance. The initial discharge capacity of 1596.2 mA h g−1 and the reversible discharge capacity of 1132 mA h g−1 can be maintained after 120 cycles at a current density of 100 mA g−1. More interestingly, the reversible capacity as high as 800 mA h g−1 can be retained at a high current density of 1000 mA g−1 after 200 cycles. Surprisingly, the pineapple-shaped ZCO electrode exhibits a prominent rate performance, a reversible specific capacity of 1237 mA h g−1 and 505 mA h g−1 at current densities of 500 mA g−1 and 6000 mA g−1 respectively. In addition, the influence of distilled water and urea on the phase and morphology of the material is investigated by SEM and EDS. The results indicate that adding distilled water into the solvent could ensure the high purity of products with no loss of the Zn element. At the same time, the cycle performance can be effectively improved because of the more regular surface and the more stable structure of the microspheres with urea-assistance.

Three-dimensional NiCo2O4 nanowire arrays: preparation and storage behavior for flexible lithium-ion and sodium-ion batteries with improved electrochemical performance

The growth of three-dimensional (3D) porous NiCo2O4 nanowire arrays on a carbon fiber cloth (denoted as NCO@CFC) via a facile low-cost solution method combined with a subsequent annealing treatment is reported. The structure and morphology of the materials were characterized by X-ray diffraction, field-emission scanning electron microscopy, and transmission electron microscopy. Owing to the unique 3D hierarchical architecture, the NCO@CFC nanowires as a flexible electrode material for lithium-ion batteries exhibit a stable cycling performance (92.3% retention after 100 cycles), a fairly high rate capacity (507 mA h g−1 at 4000 mA g−1), and an enhanced lithium storage capacity. When employed as an electrode material for sodium-ion batteries, the NCO@CFC is investigated in comparison with a 3D ordered array structure and exhibits similar charge/discharge characteristics and a feasible electrochemical performance. The greatly improved electrochemical performance could be ascribed to the 3D porous nanostructure of the NCO@CFC nanowire arrays together with a novel carbon skeleton, which provides enough space to allow volume expansion during the Li+/Na+ insertion/extraction process and facilitates rapid transport of ions and electrons.

Mesoporous ZnCo2O4 microspheres as an anode material for high-performance secondary lithium ion batteries

Herein, we report mesoporous ZnCo2O4 microspheres fabricated by a facile hydrothermal method followed by pyrolysis of a Zn0.33Co0.67CO3 precursor. The obtained ZnCo2O4 microspheres were made up of closely packed primary nanoparticles with a diameter of about 30 nm and a large number of pores that were sized between 10 to 40 nm, which results in a high BET surface area of 39.52 m2 g−1. The large surface area permits a high interfacial contact area with the electrolyte and provides more locations and channels for fast Li+ insertion/extraction into the electrode material. The porous structure may not only be beneficial for Li+ ions to diffuse efficiently to active material with less resistance but also to buffer the volume expansion during the discharging/charging processes. When used as an anode material, the specific capacity was maintained at a high value of 1256 mA h g−1 after 100 cycles at a current density of 100 mA g−1, which is about 3.4 times larger than that of the commercial graphite electrode (372 mA h g−1). More interestingly, a reversible capacity as high as 774 mA h g−1 could be retained at a high current density of 1000 mA g−1 after 200 cycles, which indicates that the mesoporous ZnCo2O4 microspheres had excellent cycling performance at a high current density for use as anode materials for lithium-ion batteries (LIBs).

PSA modified 3 D flower-like NiCo2O4 nanorod clusters as anode materials for lithium ion batteries

Novel 3-dimensional (3 D) flower-like NiCo2O4 (NCO) nanorod clusters are fabricated by a facile hydrothermal process using styrene–acrylonitrile copolymer (PSA) nanospheres as a complex agent. The structure and morphology of NCO are characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the PSA modified NCO (PNCO) exhibits excellent electrochemical performance. Compared with pure NCO, the flower-like PNCO materials with enough free space as anodes in lithium ion batteries (LIBs) deliver an initial discharge capacity of 1519.1, 1447.3 and 1337.3 mA h g−1 at the current densities of 500, 1000 and 2000 mA g−1, as well as 1417.5, 819.0 and 719.5 mA h g−1 after 100 cycles. Meanwhile, they display improved rate performance at elevated current rates, such as 1247.3, 1193.5 and 944.5 mA h g−1 at current densities of 1000, 2000 and 4000 mA g−1, respectively. They have great prospects for the application of anode materials for lithium-ion batteries.

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.

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).

Influence of Magnetron Sputtering Method on Cyclic Performance of Tin Film Anodes

Tin thin films on Cu foil substrates as the anodes of lithium ion battery were prepared by direct current (DC) and radio frequency (RF) magnetron sputtering (MS), respectively. The surface morphology and cyclic performance of the films were characterized by atomic force microscope (AFM), scanning electron microscopy (SEM), inductively coupled plasma atomic emission spectrometry (ICP) and galvanostatic charge/discharge (GC) measurements. It is found that the cyclic performance of Sn film prepared by RFMS as anode of lithium ion battery is far better than that prepared DCMS. The discharge capacity of the film prepared by DCMS changes from 748 mAh/g of 1st cycle to 99 mAh/g of 30th cycle. Nevertheless, the discharge capacity of the film prepared by RFMS changes from 653 mAh/g of 1st cycle to 454 mAh/g of 30th cycle. The better performance of the film prepared by RFMS is ascribed to the retardation of the bulk tin cracking from volume change during lithium intercalation and de-intercalation, which avoids the pulverization of tin.

Investigation on Lithiation Mechanism of Interphase Ni3Sn4 Alloy Used as Anode Material for Lithium-Ion Batteries

Sn-based anode materials have poor cycling performance due to mechanical fatigue caused by volume expansion during lithium insertion and extraction processes. In this work, the mechanism of lithium insertion/extraction in the Ni3Sn4 alloy electrode is investigated using the first-principle plane-wave pseudopotential and experimnetal method. The calculated results indicate that the Ni3Sn4 alloy phase has relatively minor expansion ratio and fluctuating electrochemical potential, which the tendency is consistent with the experimental result. On the other hand, the Sn-Ni alloy thin films with different tin content are prepared by electrodepostion on copper as an anode for lithium-ion batteries. The structural and electrochemical characteristics of Sn-Ni alloy are examined using X-ray diffraction (XRD) and repeated constant current charge/discharge (CC). The results show Tthheat Ni3Sn4 alloy phase has best cyclic stability during the lithium insertion and extraction processes.