Powering lithium-sulfur batteries by ultrathin sulfurized polyacrylonitrile nanosheets.

Sulfurized polyacrylonitrile (SPAN) is a promising cathode material for stable lithium-sulfur (Li-S) batteries due to its shuttle-free redox mechanism. However, the redox kinetics of SPAN needs to be enhanced to improve Li-S batteries. Herein, a salt-templating method is proposed for the fabrication of ultrathin SPAN nanosheets, which can afford a large contact area with the electrolyte and shorten the transport paths of electrons/ions involved in the reaction. In situ Raman analysis confirms the reversible breaking and formation of C-S/S-S bonds in SPAN nanosheets during cycling while ex situ SEM reveals the formation of lithium sulfide particles on the surface of SPAN nanosheets at the end of discharge. At a high current density of 2 A g-1, coin cells based on a SPAN nanosheet cathode can deliver a reversible capacity of 408 mA h g-1composite over 100 cycles with a capacity retention rate of 95%. Meanwhile, pouch cells using a SPAN nanosheet cathode exhibit a capacity retention rate close to 100% after 100 cycles at the same current density. These results herald a new approach for powering Li-S batteries by the nanoscale design of the SPAN cathode.