December 4, 2015 - 3:00pm - 4:00pm
The theoretically proposed graphene/single-walled carbon nanotube (G/SWCNT) hybrids by placing SWCNTs among graphene planes through covalent C-C bonding or meso 3D graphene structures are expected to be with extraordinary physical properties and promising engineering applications. Herein, Chemical vapor deposite(CVD) growth of 3D sp2 nanocarbon structure such as graphene carbon nanotube(G-CNT) hybrids, unstacked double-layer graphene (UDG), graphene nanofiber (GNF) with meso single crystal layered double oxide (LDO) or MgO as hard templates with tunable structures, surface area, pore size and the conductivity was explored. The as obtained G-CNT-S cathode exhibited excellent performance for Li-S batteries with a capacity as high as 650 mAh g-1 after 100 cycles even at a high current rate of 5 C. The UDG separated by a large amount of mesosized protuberances and can be used for high-power lithium–sulphur batteries with excellent high-rate performance. Even after 1,000 cycles, high reversible capacities of ca. 530mAh g-1 and 380mAh g-1 are retained at 5 C and 10 C, respectively.While the high conductive GNFs made from MgCO3 nanofiber hard templates have the short diffusion distance for ions of ionic liquids electrolyte to the surface which yield high surface utilization efficiency and have a capacitance up to 15 μF/cm2, higher than single-walled carbon nanotubes.
A rationally designed N-ACNT/G sandwich was proposed and fabricated via a two-step CVD growth. Aligned CNTs and graphene layers were in situ anchored to each other, constructing a sandwich-like hierarchical architecture with efficient 3D electron transfer pathways and ion diffusion channels. The moderate chemical modulation induced by nitrogen doping introduced more defects and active sites to the carbon framework, thereby improving the interfacial adsorption and electrochemical behaviors. When the novel N-ACNT/G hybrids were used as cathode materials for Li-S batteries, greatly enhanced cyclic and rate performances were demonstrated.
These types of 3D sp2 structures are expected to be an important platform that will enable the investigation of stabilized three-dimensional topological porous systems and demonstrate the potential of sp2 materials for advanced energy storage, environmental protection, nanocomposite and healthcare applications.