Effective Separation of Lithium Anode and Sulfur Cathode in Lithium-Sulfur Batteries

We demonstrate the importance of effective separation between the sulfur cathode and the lithium anode in Li-S batteries. Improved cycling stability is obtained by using fluoro-functionalized reduced graphene oxide (rGO) as a separator between the sulfur cathode and the lithium anode. The thickness of the hydrophobic interlayer is found to be 1-2 mu m. The possible mechanism is checked with analytical techniques and suggests that improvement in the capacity stability can be attributed to the reduced reactivity of long-chain polysulfides with the metallic lithium and to the homogenous distribution of end discharge products during cycling. The importance of the effective separation of lithium and sulfur is proven by using commercially available lithium conductive ceramics. Good cycling stability over 350 cycles with a coulombic efficiency above 99.95% is achieved, which demonstrates the possibility of long cycle life with proper separation of lithium and sulfur cathode.