报告题目：Breaking the Intrinsic Materials Limits for Electrical Energy Storage Using Hierarchical Core-Shell Hybrid Structures

报 告 人 ：李钧教授

报告时间：2018年9月18日（周二）下午3:00

报告地点：东三楼321会议室

邀 请 人 ：王得丽教授

报告人简介：

Dr. Jun Li obtained his Bachelor degree from Wuhan University in 1987, and received the PhD (Princeton University, 1995) and postdoc (Cornell University, 1994-1997) 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 170 peer-reviewed papers and book chapters, and edited one book on biosensors. He holds 11 issued patents. 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.

报告摘要：

   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 7 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 thick 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 high-capacity LIB materials, i.e. Si anode and V₂O₅ cathode, using this core-shell architecture. These electrode materials are well known for their fast degradation due to the high stress induced by the large volume changes during charge/discharge processes. Such mechanical failure was found to be effectively mitigated 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. Remarkably 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.