Enabling High-Energy-Density Cathode for Lithium-Sulfur Batteries.

Abstract

High-energy lithium-sulfur (Li-S) battery is built on high loading and dense sulfur electrodes. Unfortunately, these electrodes usually suffer from a low sulfur utilization rate and limited cycle life due to the gap in scientific knowledge between the fundamental research and the application at relevant scales. In this work, effects of electrode porosity on the electrode energy density, cell cycling stability, Li anode interface, and electrolyte/sulfur ratio were investigated on the basis of high-loading sulfur electrodes. Using electrodes with sulfur loading of 4 mg cm-2 and thickness at ∼60 μm, a high energy density of over 1300 Wh L-1 has been obtained at electrode level, which provides a decent basis for high-energy Li-S cell development. In addition, Li-S cells with the high-loading and dense electrodes demonstrate promising cycling stability (∼80% capacity retention for 200 cycles). These significant improvements are contributed by the synergistic effects of dense sulfur cathode, improved electrode wetting, and suppressed quick growth of the interphase layer on Li-metal anode. This study sheds light on rational design of sulfur cathode for balanced cell energy density and cycling life.