购彩中心

题目: High-performance Electrical Energy Storage Based on Hierarchical Hybrid Structures
演讲人: Jun Li, Professor of Department of Chemistry, Kansas State University, Manhattan, Kansas 66506, USA
时间：2018年6月21日（周四）15:00 
地点：购彩大厅 B楼410会议室
邀请人：王开学 研究员


Abstract:
Lithium-ion batteries (LIBs) and electrochemical supercapacitors represent today’s most successful electrochemical energy storage (EES) systems. Their performance strongly depends on the electrode materials. The common electrode materials are limited by their intrinsic properties including low specific capacity, poor electrical conductivity and slow ion diffusion. 

In the past 5-10 years, we have been investigating an effective approach to breaking these limits using a three-dimensional nanostructured core-shell architecture by depositing ~100 – 200 nm active electrode materials as coaxial shells on a highly conductive nanostructured current collector, i.e. vertically aligned carbon nanofiber arrays (~100 nm in diameter and 5 – 10 m in length).


We have demonstrated the dramatic improvement of two representative LIB materials, i.e. Si anode and V2O5 cathode, using this core-shell architecture. These two high-capacity electrode materials are well known for their fast degradation in previous studies due to the high stress induced by the large volume changes during charge/discharge processes. Such mechanical failure was found to be effectively mitigated by using the hybrid electrode structure. 

In addition, it also enables enhancing the overall electrical conductivity and shortening the diffusion path length in the solids. With proper deposition techniques, the shell materials can form secondary nanostructures, further reducing the Li+ diffusion length in solids down to ~10 nanometers. Furthermore, it provides a significant pseudocapacitive contributions associated with the fast faradaic reactions at or near the electrode surface and enables the use of disordered electrode materials. 


As a result, these hybrid LIB electrodes present the combined features of LIBs and supercapacitors. Extremely high specific capacity (3,200 – 3,500 mAh/g for Si anode and 547 mAh/g for V2O5 cathode) can be obtained even at high power rates, well exceeding today’s commercial LIBs (372 mAh/g for graphite anode and ~140 mAh/g for LiCoO2 cathode). 

These studies demonstrate the potential to break the intrinsic limits of the traditional electrode materials by using the multi-scale nanostructured hybrid materials.


Introduction of the speaker:

Prof. Jun Li is a Professor of Kansas State University, Department of Chemistry Manhattan. He received the Ph.D. and postdoc training in surface sciences and electrochemistry. He has later developed his research career on nanosciences and nanotechnologies through the employment with Molecular Imaging Co. (1997-1998), the Institute of Materials Research and Engineering (Singapore, 1998-2000), NASA Ames Research Center (2000-2007), and Kansas State University (2007 – present). 


He has published over 165 peer-reviewed papers and book chapters, and edited one book on biosensors. He holds 11 issued patents and a total of 29 patent applications.  His research work in nanotechnology has been highlighted in over 40 public news reports (including Nature, MIT Technology Review, Science, etc.). He received the first annual Nano50 Award by NASA Tech Briefs under Innovator category in 2005. Dr. Li has been serving as an associate editor (2007-2014) and senior editor (2015 – present) for IEEE Transactions on Nanotechnology.


Dr. Jun Li’s research interests are focused on integrating nanomaterials, particularly carbon nanotubes, graphene, semiconductor nanowires, and metal oxides, into functional devices for:
(1) energy conversion and storage: dye-sensitized solar cells, electrochemical supercapacitors, and Lithium-ion batteries; 
(2) nanobiosensors: nanoelectrode array based biosensors, electrical neural interfaces, and dielectrophoretic capture and detection of bacterial and viral particles; 
(3) next-generation nanoelectronics: on-chip electrical interconnects and thermal interface materials.