Xinye Qian

Separator modified by Ketjen black for enhanced electrochemical performance of lithium–sulfur batteries

A routine separator modified by a Ketjen black (KB) layer on the cathode side has been investigated to improve the electrochemical performances of Li–S batteries. The KB modified separator was prepared by a facile slurry coating method which offers a low-cost approach to solve the difficulties of Li–S batteries. Li–S cells assembled with this KB coated separator present excellent electrochemical performances in comparison with that of cells with a routine separator. The initial discharge capacity reaches 1318 mA h g−1 at 0.1C, and the reversible discharge capacity is maintained at 815 mA h g−1 after 100 cycles at 1C implying high capacity retention. Meanwhile, it achieves a discharge capacity of 934 mA h g−1 even at 2C demonstrating an excellent rate performance. Furthermore, electrochemical impedance spectroscopy (EIS) shows that the KB separator sample displays a lower charge transfer resistance which is beneficial for the electrochemical kinetics. The improved performance is supposed to be attributed to the porous architecture of the Ketjen black (KB) layer on the routine separator, which served as a physical barrier to block dissolved lithium polysulfides and an upper current collector to facilitate the transition of ions and electrons.

Nickel nanoparticles encapsulated in porous carbon and carbon nanotube hybrids from bimetallic metal-organic-frameworks for highly efficient adsorption of dyes

Nickel nanoparticles encapsulated in porous carbon/carbon nanotube hybrids (Ni/PC-CNT) were successfully prepared by a facile carbonization process using Ni/Zn-MOF as the precursor. Distinct from previous studies, Ni/Zn-MOF precursors were prepared via a direct precipitation method at room temperature for only 5min. After the carbonization, magnetic Ni nanoparticles were well embedded in the porous carbon and carbon nanotube. The obtained Ni/PC-CNT composites had a high surface area (999m2 g-1), large pore volume (0.86cm3 g-1) and well-developed graphitized wall. The Ni/PC-CNT composites showed excellent adsorption capacity for removal of malachite green (MG), congo red (CR), rhodamine B (Rh B), methylene blue (MB) and methyl orange (MO) from aqueous solution. The maximum adsorption capacity of Ni/PC-CNT composites were about 898, 818, 395, 312 and 271mg/g for MG, CR, RB, MB and MO dyes, respectively, which were much higher than most of the previously reported adsorbents. Moreover, the Ni/PC-CNT composites could be easily regenerated by washing it with ethanol and easy magnetic separation.

Zn-MOF derived micro/meso porous carbon nanorod for high performance lithium–sulfur battery

In order to solve the problems of poor cycling stability and low coulombic efficiency in lithium–sulfur battery, induced by the low conductivity of sulfur and the shuttle effect of soluble polysulfides, a unique micro/meso porous carbon nanorod (MPCN) was fabricated by carbonizing a zinc metal–organic framework (Zn-MOF) precursor, which was prepared by a facile aqueous solution method at room temperature. The mesopores in the MPCN are beneficial for the infiltration of electrolyte and the transportation of Li ions, and the micropores are sufficient to encapsulate sulfur and adsorb the soluble polysulfides. The MPCN–S cathode displays a discharge capacity of about 1000 mA h g−1 at the current rate of 0.5C and retains 740 mA h g−1 after 200 cycles with the coulombic efficiency up to 95%. Moreover, it still has a discharge capacity as high as 850 mA h g−1 when the current rate increased to 2C, which demonstrates a nice rate capability.

CeO2 nanodots decorated ketjen black for high performance lithium–sulfur batteries

A CeO2 nanodots decorated ketjen black composite was fabricated by a simple wet impregnation method and used as the host of sulfur for a lithium–sulfur battery. The microstructure and chemical components were evaluated by XRD, SEM, TEM, surface area analysis and thermogravimetric analysis. Electrochemical tests and microanalysis demonstrated that CeO2 nanodots served as the sulfur fixation spots as well as the catalytic agent compared with the reference sample without CeO2 nanodots. The CeO2/KB–S cathode material with the CeO2/KB mass ratio of approximately 15/85 shows a high initial discharge capacity of 905 mA h g−1 at the current rate of 1C and remains at 710 mA h g−1 after 300 cycles. Furthermore, the CeO2/KB–S cathode shows a promising rate performance with the discharge capacity of 800 mA h g−1 even at the current rate of 2C.

Superior adsorption performance of metal-organic-frameworks derived magnetic cobalt-embedded carbon microrods for triphenylmethane dyes

In this work, magnetic Co/C microrods were successfully synthesized using direct carbonization of [Co3(BTC)2(H2O)12] precursors. After the carbonization, the original shape of the precursors was well-maintained, while the magnetic Co nanoparticles were well dispersed in the carbon matrix. The Co/C microrods were used as adsorbents for the adsorption of methyl blue (MB), acid fuchsin (AF), malachite green (MG), rhodamine B (Rh B), methyl orange (MO) and methylene blue (MTB) from their aqueous solutions. The results show that Co/C microrods can selectively adsorb triphenylmethane (TPM) dyes, while the adsorption capacities are about 13960, 11,610 and 4893 mg/g for MB, AF and MG dyes, respectively. The adsorption mechanism can be attributed to π-π interaction forces between the sp2 graphitic carbon in Co/C microrods and the triphenyl structure of dyes. In addition, the synthesized magnetic Co/C microrods can be easily removed from water using magnetic separation, and subsequently, regenerated using ethanol treatment.