Graphene quantum dots: structural integrity and oxygen functional groups for high sulfur/sulfide utilization in lithium sulfur batteries

Lithium–sulfur (Li–S) batteries are expected to overcome the limit of current energy storage devices by delivering high specific energy with low material cost. However, the potential of Li–S batteries has not yet been realized because of several technical barriers. Poor electrochemical performance is mainly attributed to the low electrical conductivity of the fully charged and discharged species, the irreversible loss of polysulfide anions and the decrease in the number of electrochemically active reaction sites during battery operation. Here, we report that the introduction of graphene quantum dots (GQDs) into the sulfur cathode dramatically enhanced sulfur/sulfide utilization, yielding high performance. In addition, the GQDs induced structural integrity of the sulfur–carbon electrode composite by oxygen-rich functional groups. This hierarchical architecture enabled fast charge transfer…