A systematic approach to high and stable discharge capacity for scaling up the lithium–sulfur battery

Abstract

A systematic approach to improving the performance of the Li–S battery is presented, based on applying high energy ball milling to create a porous sulfur–carbon composite, insertion of a free-standing layer, and adoption of a new charging method. Surface area analysis and field emission scanning electron microscope imaging show that the ball-milled sulfur powder has a porous structure and very high specific surface area. A vacuum-filtrated single-walled carbon nanotube free-standing layer is inserted in between the sulfur cathode and the separator. It is believed that high-surface-area porous sulfur will help to increase the conductivity of the elemental sulfur due to better adhesion between the conducting carbon and the sulfur, while the free-standing layer will sequester longer chain polysulfides, which are responsible for the well-known shuttling phenomenon. By the combination of these methods, we have achieved excellent capacity and cycle life. Finally, a new charging method which will largely prevent the formation of longer chain polysulfides is also applied to increase the capacity retention. It is believed that with the combination of ball milling, the free-standing layer, and the new charging method, it is possible to commercialize the Li–S battery with better capacity and cycle life.