Carbon-Nanotube-Encapsulated-Sulfur Cathodes for Lithium-Sulfur Batteries: Integrated Computational Design and Experimental Validation.

To mitigate lithium-polysulfides (Li-PSs) shuttle in lithium-sulfur batteries (LiSBs), a unique carbon-nanotube-encapsulated-sulfur (S@CNT) cathode material with optimum open-ring sizes (ORSs) on the CNT walls were designed using an integrated computational approach followed by experimental validation. By calculating the transport barrier of Li ion through ORSs on the CNT walls and comparing the molecular size of solvents and Li-PSs with ORSs, optimum open-rings with 16-30 surrounding carbon atoms were predicted to selectively allow transportation of Li ion and evaporated sulfur while blocking both Li-PS and solvent molecules. A CNT oxidation process was proposed and simulated to generate these ORSs, and the results indicated that the optimum ORSs can be achieved by narrowly controlling the oxidation parameters. Subsequently, S@CNT cathodes were experimentally synthesized, confirming that optimum ORSs were generated in CNT oxidized at 475 K and exhibited more stable cycling behavior.