Haosen Fan

General Approach for MOF-Derived Porous Spinel AFe2O4 Hollow Structures and Their Superior Lithium Storage Properties

A general and simple approach for large-scale synthesis of porous hollow spinel AFe2O4 nanoarchitectures via metal organic framework self-sacrificial template strategy is proposed. By employing this method, we can successfully synthesize uniform NiFe2O4, ZnFe2O4, and CoFe2O4 hollow architectures that are hierarchically assembled by nanoparticles. When these hollow microcubes were tested as anode for lithium ion batteries, good rate capability and long-term cycling stability can be achieved. For example, high specific capacities of 636, 449, and 380 mA h g(-1) were depicted by NiFe2O4, ZnFe2O4, and CoFe2O4, respectively, at a high current density of 8.0 A g(-1). NiFe2O4 exhibits high specific capacities of 841 and 447 mA h g(-1) during the 100th cycle when it was tested at current densities of 1.0 and 5.0 A g(-1), respectively. Discharge capacities of 390 and 290 mA h g(-1) were delivered by the ZnFe2O4 and CoFe2O4, respectively, during the 100th cycle at 5.0 A g(-1).

Co9S8/MoS2 Yolk–Shell Spheres for Advanced Li/Na Storage

Uniform sized Co9 S8 /MoS2 yolk-shell spheres with an average diameter of about 500 nm have been synthesized by a facile route. When evaluated as anodes for lithium-ion and sodium-ion batteries, these Co9 S8 /MoS2 yolk-shell spheres show high specific capacities, excellent rate capabilities, and good cycling stability.

Controllable Preparation of Square Nickel Chalcogenide (NiS and NiSe2) Nanoplates for Superior Li/Na Ion Storage Properties

A facile and bottom-up approach has been presented to prepare 2D Ni-MOFs based on cyanide-bridged hybrid coordination polymers. After thermally induced sulfurization and selenization processes, Ni-MOFs were successfully converted into NiS and NiSe2 nanoplates with carbon coating due to the decomposition of its organic parts. When evaluated as anodes of Li-ion batteries (LIBs) and Na-ion batteries (NIBs), NiS and NiSe2 nanoplates show high specific capacities, excellent rate capabilities, and stable cycling stability. The NiS plates show good Li storage properties, while NiSe2 plates show good Na storage properties as anode materials. The study of the diffusivity of Li(+) in NiS and Na(+) in NiSe2 shows consistent results with their Li/Na storage properties. The 2D MOFs-derived NiS and NiSe2 nanoplates reported in this work explore a new approach for the large-scale synthesis of 2D metal sulfides or selenides with potential applications for advanced energy storage.

Sn Nanoparticles Encapsulated in 3D Nanoporous Carbon Derived from a Metal–Organic Framework for Anode Material in Lithium-Ion Batteries

Three-dimensional nanoporous carbon frameworks encapsulated Sn nanoparticles (Sn@3D-NPC) are developed by a facile method as an improved lithium ion battery anode. The Sn@3D-NPC delivers a reversible capacity of 740 mAh g-1 after 200 cycles at a current density of 200 mA g-1, corresponding to a capacity retention of 85% (against the second capacity) and high rate capability (300 mAh g-1 at 5 A g-1). Compared to the Sn nanoparticles (SnNPs), such improvements are attributed to the 3D porous and conductive framework. The whole structure can provide not only the high electrical conductivity that facilities the electron transfer but also the elasticity that will suppress the volume expansion and aggregation of SnNPs during the charge and discharge process. This work opens a new application of metal-organic frameworks in energy storage.

Controllable synthesis of various V2O5 micro-/nanostructures as high performance cathodes for lithium ion batteries

The orthorhombic layer structured vanadium oxide, V2O5, is an attractive material for many essential applications. Here, a series of vanadium pentoxide micro-/nanostructures were prepared via a simple solvothermal approach followed by an annealing process. Various morphological structures from core–shell microspheres, nanosheets, hierarchical microflowers to octahedron structures can be tuned by simply changing the solvent ratio among dimethylformamide (DMF), isopropyl alcohol (IPA) and acetic acid. V2O5 microflowers and octahedra were investigated as cathodes for LIBs and showed good cycling stabilities and excellent ultrahigh rate capabilities.

Hydrogenated vanadium oxides as an advanced anode material in lithium ion batteries

Current research on vanadium oxides in lithium ion batteries (LIBs) considers them as cathode materials, whereas they are rarely studied for use as anodes in LIBs because of their low electrical conductivity and rapid capacity fading. In this work, hydrogenated vanadium oxide nanoneedles were prepared and incorporated into freeze-dried graphene foam. The hydrogenated vanadium oxides show greatly improved charge-transfer kinetics, which lead to excellent electrochemical properties. When tested as anode materials (0.005–3.0 V vs. Li/Li+) in LIBs, the sample activated at 600 °C exhibits high specific capacity (∼941 mA·h·g−1 at 100 mA·g−1) and high-rate capability (∼504 mA·h·g−1 at 5 A·g−1), as well as excellent cycling performance (∼285 mA·h·g−1 in the 1,000th cycle at 5 A·g−1). These results demonstrate the promising application of vanadium oxides as anodes in LIBs.

Molten sodium-induced graphitization towards highly crystalline and hierarchical porous graphene frameworks

Mass production of high quality graphene platelets has attracted considerable interest for potential applications in various fields. Nevertheless, in literature, the graphite oxide (GO)-derived graphene is always lacking high crystallinity and hierarchical porosity. Herein, we report a new molten sodium-induced graphitization for mass-fabricating highly crystalline and porous graphene sheets. The 3D graphene hydrogels (GHs) obtained from GO by the hydrothermal self-assembly are directly annealed in molten sodium at 800 °C. As a result, the D band intensity in Raman spectroscopy is reduced significantly, while 2D band intensity is increased prominently, which is a typical characteristic of highly crystalline graphene. More importantly, the resulting Na-GFs-800 sample exhibits increased surface area and narrow mesopore size distribution (~3.6 nm). The excellent supercapacitive performance of Na-GFs-800 has been demonstrated in an organic symmetric system. Meanwhile, the possible interaction mechanism between molten sodium and GHs has been proposed in the text.