Yan YuUniversity of Science and Technology of China, China
Dr. Yan Yu received her Ph.D. in material science at USTC in 2006. From 2007 to 2008, she worked as a postdoctoral at Florida International University. After that she received Humboldt Research Fellow and the Sofja Kovalevskaja award from the Alexander von Humboldt Foundation and worked at the Max Planck Institute for Solid State Research in Stuttgart, Germany. Her current research interests mainly include design of novel nanomaterials for clean energy, especially for batteries and the fundamental science of energy storage system. Dr. Yu already published over 80 peer-reviewed papers on Adv. Mater., JACS, Angew. Chemie, Adv. Funct. Mater., Adv. Energy Mater., ACS Nano, Nano Lett etc.
Title：Graphene-based composites as advanced electrodes for energy storage
SymposiumB13 Lithium Ion Batteries
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Abstract
Graphene, a 2D single-layer graphite sheet, exhibits many unique and amazing properties such as high electrical conductivity, high surface area, and excellent chemical stability. These properties make graphene a good carbon candidate to improve the electrochemical properties of lithium-ion and sodium-ion electrode materials through building 3D conductive graphene-network. However, graphene sheets are easy to agglomerate, leading to an unsatisfied improved effect on graphene-based electrode materials. On the other hand, the active electrode materials based on different storage mechanism further propose other requirements for conductive graphene networks. For example, Sn-based materials, metal oxides, and metal sulfides with high theoretical capacity undergo large volume changes during lithiation/delithiation, and thus destroy the graphene networks. As a consequence, these graphene-based composites show low capacity release and poor cycle life. Currently, it is necessary and remains a challenge to design and construct reasonable nanostructures for graphene-based composites based on different storage mechanisms.
In this study, for the NASICON-type NaTi2(PO4)3 (NTP) and Na3V2(PO4)3 (NVP) materials based on phase transformation,1,2 we have designed and synthesized an architecture that comprises embedded porous NTP nanoparticles in a 3D graphene network (denoted as 0D-NTP3D-GN) and another architecture consisting of NVP nanocrystals coated with amorphous carbon and then wrapped by reduced graphene oxide nanosheets (denoted as NVP@C@rGO). 3D graphene networks greatly increases the electron/ion transport kinetics and assures the electrode structure integrity, leading to attractive electrochemical performances in terms of high rate-capability, long cycle-life as well as high initial Coulombic efficiency.
For the Sn-based composites with large volume changes on cycling,3 we present three-dimensional (3D) porous graphene network-encapsulated Sn-based architectures. The pre-existing interconnected nano-sized pores provide the necessary void space for expansion of Sn-based particles, preventing them from destroying the 3D framework on cycling, and allowing for fast transport of Li-ions via electrolyte filling into the percolating free interstices. 3D conductive graphene framework can counteract self-aggregation of nanoparticles, facilitate electron transfer, and stabilize solid electrolyte interface (SEI) formation. As a consequence, the obtained composites exhibit high reversible capacity and fast rate-capability, as well as ultralong cycle life.
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