Guest Introduction
Prof. Gao Liu is the Group Leader of the Applied Energy Materials Group in the Energy Technologies Area at Lawrence Berkeley National Laboratory, specialized in energy storage R&D. He received a Bachelor's degree from Beijing University in 1993, and a Ph.D. in Chemistry from Michigan State University in 2001.  He was a postdoctoral fellow from 2001 to 2003 at the Lawrence Berkeley National Laboratory, and then became term scientist in 2003, career scientist in 2004, and principal investigator in 2005 in the Environmental Energy Technologies Division. Now Dr. Liu has led research projects for the U.S. Department of Energy and industry. He has over 100 peer-reviewed publications and over 20 patents and patent applications. He has received numerous awards from his work on electrochemical energy storage materials and systems. The most recent awards include R&D100 Award in 2013 for conductive polymer for lithium-ion battery application, and FMC Scientific Achievement Award in 2014 for understanding fundamental of prelithiation, and R&D 100 Award in 2015 for high capacity lithium ion anode design.

Development of High Area Loading and Stable Sulfur Electrode Through Interface Functionality Design for Lithium Sulfur Battery
High area loading of sulfur is a critical parameter to achieve high energy-density Li-S battery. Interface properties between electrode and electrolyte play an important role in these batteries. Sulfur species dissolution, precipitation and phase transformation during the charge and discharge process strongly affect the performance of lithium sulfur (Li-S) batteries. In this work, we examine the chemical functionalities that are important to stabilize sulfur electrode. As an example, binders with different functionalities, which differs both in chemical and electrical properties, are employed to modify the interface between the conductive matrix and electrolyte. The phase transformation of sulfur species at this interface is studied in detail. Remarkable differences are observed among sulfur cathodes with different binders modified interface. More solid-phase sulfur species precipitation is observed with binders that have strong affiliate functional groups, like poly(9, 9-dioctylfluorene-co-fluorenone-co-methylbenzoic ester) (PFM) and poly(vinylpyrrolidone) (PVP), in both fully charged and discharged states. Also, the improved conductivity from introducing conductive binders greatly promotes sulfur species precipitation. These findings suggest that the contributions from functional groups affinity and binder conductivity lead to more sulfur transformation into the solid phase, so the shuttle effect can be greatly reduced, and higher sulfur area loading and better cycling stability can be obtained.