Guijing Liu

A facile hydrothermal synthesis of a reduced graphene oxide modified cobalt disulfide composite electrode for high-performance supercapacitors

In this study, a 3D reduced graphene oxide modified CoS2 composite electrode (CoS2/RGO) is synthesized by a facile hydrothermal approach. The dimensions of the CoS2 nanoparticles in CoS2/RGO are effectively reduced due to the geometric confinement of RGO, and a novel, large-scale wave-like structure is formed. This leads to an enlarged specific surface area and improved conductivity and could thus be favourable for both fast electron and ion transport. As a consequence, CoS2/RGO displays better electrochemical properties than the pure individual components. When the mass ratio of CoCl2·6H2O and GO as the raw materials is 1 : 2, the obtained CoS2/RGO composite electrode (CoS2/RGO-2) delivers the highest capacitance of 930.3 F g−1 at 2 A g−1 and retains a capacitance as high as 677.9 F g−1 as the current density increases up to 20 A g−1. Moreover, in order to obtain high energy and power densities, a high-voltage asymmetric supercapacitor has been designed and constructed using the optimized CoS2/RGO-2 composite electrode as the positive electrode and activated carbon (AC) as the negative electrode material. Such a device with an operational voltage of 1.6 V can achieve a remarkable energy density of 45.7 W h kg−1 at a power density of 797.0 W kg−1, in addition to the superior rate capability and prominent stability towards long time charge–discharge cycles.

Carbon nanotube decorated NaTi2(PO4)3/C nanocomposite for a high-rate and low-temperature sodium-ion battery anode

A sodium super-ionic conductor structure NaTi2(PO4)3 has been considered as a promising anode material for sodium-ion batteries. However, the inherent poor electronic and ionic kinetics leading to inferior rate and low-temperature performance severely restricts its extensive developments. In this work, we report a carbon nanotube decorated nano-NaTi2(PO4)3/C anode composite to achieve high-rate capability (116.8 mA h g−1 at 1C, 113.3 mA h g−1 at 10C and 103.4 mA h g−1 at 50C) and stable cyclability (about 98% capacity retention at 50C of 1000 cycles) as well as impressive low-temperature performance (about 65.2 mA h g−1 at 10C at a temperature of minus 20 °C). The carbon nanotube network not only improved electrolyte infiltration to decrease the internal diffusion resistance, but also provides fast transport pathways for electrons to enhance the poor electronic conductivity of the NaTi2(PO4)3 anodes. In view of the advantages of the electrode architecture design, we anticipate that the nanocomposites might be promising anode materials for long-life and low-temperature rechargeable sodium-ion batteries.

Facile controlled synthesis of a hierarchical porous nanocoral-like Co3S4 electrode for high-performance supercapacitors

A facile one-step hydrothermal process is developed to synthesize a porous nanocoral-like Co3S4, which directly grows on a three dimensional (3D) macroporous nickel (Ni) foam. The scanning electron microscopy (SEM) images reveal the uniform formation of a Co3S4 nanocoral cluster on Ni foam with a hierarchical porous structure. The crystal growth mechanism and factors that influence the formation of the coral-like Co3S4 directly on Ni foam have been further studied. The subsequent electrochemical measurements demonstrate that the nanocoral-like Co3S4 as a binder-free electrode for supercapacitors possesses a large specific capacitance as high as 1559 F g−1 at a current density of 0.5 A g−1 in 2.0 M KOH aqueous electrolyte. Moreover, to confirm its practical application, an asymmetric supercapacitor is assembled with the nanocoral-like Co3S4 electrode as the positive electrode and activated carbon (AC) as the negative electrode. Such a device achieves a high energy density of 60.1 W h kg−1 at a power density of 418.2 W kg−1 and maintains 38.5 W h kg−1 at a high power density of 3812.5 W kg−1, suggesting that the presented nanocoral-like Co3S4 electrode not only has potential for applying in high energy density fields, but also in high power density applications.

Preparation and characterization of surface molecularly imprinted film coated on a magnetic nanocore for the fast and selective recognition of the new neonicotinoid insecticide paichongding (IPP)

In this work, we present a general method to prepare surface molecularly imprinted film on a magnetic nanocore for new neonicotinoid insecticide paichongding (IPP) recognition. First, magnetic Fe3O4 nanoparticles were synthesized by a hydrothermal method and coated with SiO2 on the surface, then were vinyl-modified to be Fe3O4@SiO2@CC which was the magnetic core. After that, magnetic molecularly imprinted nanoparticles (MMIPs) were synthesized by surface-imprinted polymerization in airtight tubes at 60 °C for 24 h, using IPP as the template, methacrylic acid as the functional monomer and ethylene glycol dimethacrylate as cross-linkers. The resulting IPP-MMIPs possess specific recognition ability, fast adsorption kinetics, high adsorption capacity, and can be easily collected under an external magnetic field. The IPP-MMIPs were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). The binding experiments showed a relatively high adsorption capacity (17.30 mg g−1) and specific recognition ability over structurally related compounds. Therefore, IPP-MMIPs have the potential to become a sensitive and selective approach for IPP recognition and separation.

Li3V2(PO4)3 as a cathode additive for the over-discharge protection of lithium ion batteries

Li3V2(PO4)3 has been used as a cathode additive to make lithium ion batteries (LIBs) retain a good electrochemical performance under over-discharge conditions. Its lower discharge voltage plateau effectively prevents the corrosion of anode collector-copper foil during the over-discharge progress. When 7 wt% Li3V2(PO4)3 is added to LiCoO2 through a “layer to layer” mode, the capacity retention ratio of the LIBs has raised from 49.55% to 95.91%.