Thursday, 17 October 2019: 14:40
Room 217 (The Hilton Atlanta)
Many problems of Li-S batteries essentially root in their polysulfide intermediates. While conventional wisdom mainly focuses on trapping polysulfides at the cathode using various functional materials, few strategies are available at present to fully resolve or circumvent this long-standing issue. In this study, we propose the concept of sulfur-equivalent cathode materials, and demonstrate the great potential of amorphous MoS3 as such a material for room-temperature Li-S and Na-S batteries. When evaluated in Li-S batteries, MoS3 exhibits sulfur-like behavior with large reversible specific capacity when normalized to the sulfur weight (~1400 mAh/gS at 50 mA/gS), excellent cycle life (~850 mAh/gS after 1000 cycles at 1 A/gS), exceptional high rate capability (420 mAh/gS at 20 A/gS) and possibility to achieve high areal capacity (~2.8 mAh/cm2). Most remarkably, it is also fully cycleable in the carbonate electrolyte under a relatively high temperature of 55oC. MoS3 can also be used as the cathode material of even more challenging Na-S batteries to enable an unprecedented performance. In-situ XAS experiments evidence that MoS3 preserves its chain-like structure free of polysulfide intermediates during repetitive battery cycling.