Pengfei Hu

Hydrothermal preparation, growth mechanism and supercapacitive properties of WO3 nanorod arrays grown directly on a Cu substrate

Well-oriented hexagonal WO3 nanorod arrays (h-WNRs) with an average diameter of 150 ± 50 nm and a length of 2.0–3.0 μm have been successfully realized on a Cu substrate on a large scale via a simple hydrothermal method without organic additives and substrate pre-treatment. The morphology, crystallinity, atomic composition and chemical state of WNRs are investigated by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The morphology evolution and growth mechanism of well-aligned WNRs are intensively studied. Moreover, the supercapacitive properties of WNRs with different diameters and aspect ratios are also examined. WNRs exhibit excellent cycling stability and reversibility (97%), a high specific capacitance (463 F g−1) at a current density of 1.0 A g−1, and a lower charge transfer resistance (0.8 Ω).

V2O5 nanobelt arrays with controllable morphologies for enhanced performance supercapacitors

Ordered V2O5 nanobelt arrays (VNBs) vertically grown on Ni foam have been realized by one-step hydrothermal method without any additives. The obtained VNBs are a single crystal with a two-dimensional (2D) layered structure. The morphology evolution and growth mechanism of VNBs are discussed at different hydrothermal times. The morphologies, length–width ratios and sizes of materials can be controlled by simply adjusting vanadium source concentrations, pH values and hydrothermal temperatures. Moreover, these morphology parameters can significantly affect specific capacitance, cycle stability and charge transfer resistance. Due to the ordered arrangement, single-crystal, top–down and layered structure, VNBs have a relatively high ion storage capacity, specific capacitance (498 F g−1), cycling stability (88.8%) after 5000 cycles and low charge transfer resistance (14.2 Ω) as binder-free electrode materials, which reveals a great potential for practical application in energy storage devices.

Solvothermal Synthesis of a Hollow Micro-Sphere LiFePO4/C Composite with a Porous Interior Structure as a Cathode Material for Lithium Ion Batteries

To overcome the low lithium ion diffusion and slow electron transfer, a hollow micro sphere LiFePO4/C cathode material with a porous interior structure was synthesized via a solvothermal method by using ethylene glycol (EG) as the solvent medium and cetyltrimethylammonium bromide (CTAB) as the surfactant. In this strategy, the EG solvent inhibits the growth of the crystals and the CTAB surfactant boots the self-assembly of the primary nanoparticles to form hollow spheres. The resultant carbon-coat LiFePO4/C hollow micro-spheres have a ~300 nm thick shell/wall consisting of aggregated nanoparticles and a porous interior. When used as materials for lithium-ion batteries, the hollow micro spherical LiFePO4/C composite exhibits superior discharge capacity (163 mAh g−1 at 0.1 C), good high-rate discharge capacity (118 mAh g−1 at 10 C), and fine cycling stability (99.2% after 200 cycles at 0.1 C). The good electrochemical performances are attributed to a high rate of ionic/electronic conduction and the high structural stability arising from the nanosized primary particles and the micro-sized hollow spherical structure.