Aminomethyl-Functionalized Carbon Nanotubes as a Host of Small Sulfur Clusters for High-Performance Lithium-Sulfur Batteries.

Here we propose an effective strategy to stabilize small sulfur species by using aminomethyl-functionalized carbon nanotubes (AM-CNT) without impairing the conductive channel of the carbon nanotube (CNT) cathode. The linear S clusters can be anchored strongly to the AM-CNT for the favorable size of n=5 and the maximum size of n=6 in the production of the cathode, which depresses the mass loss of active sulfur effectively and eliminates the formation of high-order polysulfides completely during the discharge process. The most stable 3 D cross-linked Inter-S -AM-CNT network shows a fast electron transfer redox reaction through the CNT skeleton that possesses a theoretical capacity of 1337 mA h g (based on sulfur) or 592 mA h g (based on the cathode). The discharge products of the linear S cluster tend to form a hyperbranched tight structure through N⋅⋅⋅S⋅⋅⋅Li bridges that are fully impregnated in the AM-CNT bundles, and thus stabilize the entire system. Importantly, this study provides vital guidance into how to design cathodes based on small sulfur clusters for Li-S batteries to depress the shuttle effect intrinsically during charge-discharge cycles, which can be extended to the other small-sulfur-cluster-based batteries.