报告人：Professor Jun Li
Jun Li , Ph.D.
Department of Chemistry, Kansas State University
Manhattan, Kansas 66506, USA
题目：Nanoarchitectured Electrode Materials for Electrical Energy Storage
Today’s high-performance electrochemical energy storage (EES) are represented by the high energy capacity of lithium-ion batteries (LIBs) and the high power and long cycle life of supercapacitors. At present, they are not able to be integrated into one system due to the distinct electrochemical mechanisms. The performance of the common electrode materials is limited by their low electrical conductivity and slow ion diffusion inside the electrode. In recent studies, we have demonstrated an effective approach to overcome these two issues based on a three-dimensional nanostructured core-shell architecture consisting of ~100 – 200 nm thick coaxially coated electroactive materials (such as Si,1, 2 TiO2, and LiCoO2, and MnO2) on a highly conductive nanostructured current collector, i.e. vertically aligned carbon nanofiber arrays. In LIBs, this hybrid electrode structure allows mitigating the slow Li+ diffusion by shortening the diffusion length in solid electrode materials. With proper deposition techniques, the shell materials can form finer nanoporous structures (such as nanoneedles, nanoflowers, etc.), further reducing the Li+ diffusion length down to ~10 nanometers. In addition, it provides another benefit due to the significant pseudocapacitive contributions associated with the fast faradaic reactions at or near the electrode surface. As a result, these LIB electrodes present the features of a battery-supercapacitor hybrid that can offer high specific energy at very high power rates. For traditional supercapacitor materials such as MnO2,3, 4 this core-shell nanoarchitecture is able to significantly improve the current collecting capabilities and further enhance the power density by orders of magnitude. These studies demonstrated the potential for multi-scale nanostructured EES electrodes to achieve stable long charge-discharge cycles in the supercapacitor power regime (i.e. completing charging or discharging in less than 1 min.) while maintaining the battery-like high energy capacity.
1. S. A. Klankowski, R. A. Rojeski, B. A. Cruden, J. Liu, J. Wu and J. Li, J. Mater. Chem. A, 2013, 1, 1055-1064.
2. S. A. Klankowski, G. P. Pandey, B. A. Cruden, J. Liu, J. Wu, R. A. Rojeski and J. Li, J. Power Sources, 2015, 276, 73-79.
3. J. Liu, J. Essner and J. Li, Chem. Mater., 2010, 22, 5022-5030.
4. S. A. Klankowski, G. P. Pandey, G. Malek, C. R. Thomas, S. L. Bernasek, J. Wu and J. Li, Nanoscale, 2015, In press.
Jun Li, Ph.D.