Synthesis and High Performance for Electrochemical Energy Conversion and Storage
Topic: Doped Graphene Composites: Synthesis and High Performance for Electrochemical Energy Conversion and Storage
Speaker: Prof. Yanglong Hou
Time: 2013-07-16¤é,10¡G00 am
Inviter: Prof. Zhang Junliang
Transition metallic sulfides have great potential applications in lithium ion batteries (LIBs) due to the peculiar electronic properties and high theoretical capacities. However, the synthesis of pure phase Ni3S4 is a great challenge due to the presence of mixed-phases, which has become a major obstacle to explore its potential applications. Herein, we report a facile, one-pot, hydrothermal synthesis to produce phase-controlled Ni3S4 nanoparticles (NPs) grown on nitrogen-doped graphene (NG) sheets. Annealing treatment was further used to achieve the better electrochemical coupling of Ni3S4/NG composite. Interestingly, we found that the annealing process at 350 „aC resulted in the formation of another high temperature stable phase of nickel sulfide, NiS1.03/NG. It is worth noting that Ni3S4/NG composites as anode materials showed 98.87% capacity retention with a discharge capacity of 1323.2 mAh/g at 100th cycle. In another work, a facile hydrothermal process was employed to grow Co3S4 nanotubes (NTs) on graphene (G) sheets. The electrochemical impedance spectroscopy (EIS) characterization verified that graphene dramatically increased the conductivity of composites, almost twice than the original one. Electrochemical measurement indicated that the as-synthesized Co3S4/G composites exhibited good cyclic stability and high discharge capacity of 720mAh/g up to 100 cycles with 99.9% columbic efficiency. Furthermore, the composites follow 4 and 2 electron path ways towards dissolved oxygen in both acidic and basic medium with an onset potential near to the commercial Pt/C in ORR. The stability of the composites is much higher than that of Pt/C, possessing high methanol tolerance.  It is expected that the synthetic methodology developed here would be a general strategy for the synthesis of transition metallic chalcogenides/NG composites.[3-7]
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