Performance enhancement of a graphene-sulfur composite as a lithium-sulfur battery electrode by coating with an ultrathin Al2O3 film via atomic layer deposition

A graphene-sulfur (G-S) composite was conformally coated with an ultrathin Al2O3 film via atomic layer deposition (ALD) and used as the cathode of a lithium-sulfur (Li-S) battery. The G-S composite cathode with an ALD-Al2O3 coating delivered a high specific capacity of 646 mA h g(-1) after 100 charge-discharge cycles at 0.5 C, and this value is about twice that of the bare G-S composite. The rate capability and coulombic efficiency of the G-S composite electrode were also greatly increased. The ALD-Al2O3 coating worked as an artificial barrier to suppress the dissolution of polysulfides and alleviate the shuttle effect; thus, it effectively improved the performance of a G-S composite cathode in a Li-S battery.