凯发_Fei Wei

Speaker-Fei Wei

Fei Wei
Tsinghua University, China

Fei Wei Cheungkong scholar Professor, he obtained his PhD in chemical engineering from China University of Petroleum in 1990. After a postdoctoral fellowship at Tsinghua University (China), he was appointed an associate professor in 1992 and professor of chemical engineering of Tsinghua University (China) in 1996. His scientific interests are technological applications of chemical reaction engineering, multiphase flow, carbon nano materials, and sustainable energy. He hasdesigned and successfully running over 30 industrial fluidized bed reactors, and authored three books and over 500 refereed publications with more than 20000 citations.

Title：1.Mechanical Energy Storage and Absorbing Materials Based on SP2 Carbon Structure 2.CVD Growth of 3D sp2 Structures and Its Applicationfor Supercapacitor

SymposiumB3 Graphene/GO Manufacture Technology & A3 Other 2D Materials

Starting Time

Ending Time

Abstract

1.Mechanical energy storage is also one of the most important ways for energy conversion. In fact, water reservoirs on high mountains store mechanical energy using the gravitational potential on the earth, and the surplus energy can be mechanically stored in water pumped to a higher elevation using pumped storage methods.

Here we experimentally demonstrate that the as-grown defect-free CNTs with length over 10 cm, have breaking strain up to 17.5%, tensile strength up to 120 GPa and Young’s modulus up to 1.34 TPa. They could endure a continuously repeated mechanical strain-release test for over 1.8×108 times. The extraordinary mechanical performance qualifies them with high capacity for the storage of mechanical energy. The CNTs can store mechanical energy with a density as high as 1125 Wh kg-1 and a power density as high as 144 MW kg-1 , indicating the CNTs can be a promising medium for the storage of mechanical energy.

The selection of resilient and robust building blocks is the first step for high energy-density mechanical energy storage system. Herein, alternative aligned carbon nanotubes(CNTs) and graphene were effectively sandwiched into free standing sp2 all-carbon hybrids, rendering the excellent loading transfer in the three-dimensional framework. The millimeter-scale aligned CNT/graphene sandwiches could be repeatedly compressed at high strains (ε490%), with a highest energy absorption density of 237.1kJ/kg-1, an ultrahigh power density of 10.4kWkg-1, and a remarkable efficiency of 83% during steady operation, providing novel nanocomposites with outstanding mechanical energy storage performance comparable to electrochemical batteries and bridging nanoscopic structures to micro- and mesoscale applications.

2.The theoretically proposed graphene/single-walled carbon nanotube(G/SWCNT) hybrids by placing SWCNTs among graphene planes through covalentC-C bonding or meso 3D graphene structures are expected to be with extraordinary physical properties and promisingengineering 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), graphenenanofiber(GNF) with meso single crystal layered double oxide (LDO)or MgO as hard templates with tunable structures, surface area, pore sizeand the conductivity was explored.The as obtained G-CNT-S cathode exhibited excellentperformance for Li-S batteries with a capacity as high as 650 mAh g-1 after 100 cycleseven at a high current rate of 5 C.The UDG separated by a large amount of mesosized protuberances and canbe used for high-power lithium–sulphur batteries with excellent high-rate performance. Evenafter 1,000 cycles, high reversible capacities of ca. 530mAh g-1 and 380mAh g-1 areretained 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 liquidselectrolyte to the surface which yield high surfaceutilization 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 sp2structuresare expected to bean important platform that will enable the investigation of stabilized three-dimensionaltopological porous systems and demonstrate the potential of sp2 materialsfor advanced energy storage, environmental protection, nanocomposite and healthcareapplications.