Amidation-Dominated Re-Assembly Strategy for Single-Atom Design/Nano-Engineering: Constructing Ni/S/C Nanotubes with Fast and Stable K-Storage.

An amidation-dominated re-assembly strategy is developed to prepare uniform single atom Ni/S/C nanotubes. In this re-assembly process, a single-atom design and nano-structured engineering are realized simultaneously. Both the NiO5 single-atom active centers and nanotube framework endow the Ni/S/C ternary composite with accelerated reaction kinetics for potassium-ion storage. Theoretical calculations and electrochemical studies prove that the atomically dispersed Ni could enhance the convention kinetics and decrease the decomposition energy barrier of the chemically-absorbed small-molecule sulfur in Ni/S/C nanotubes, thus lowering the electrode reaction overpotential and resistance remarkably. The mechanically stable nanotube framework could well accommodate the volume variation during potassiation/depotassiation process. As a result, a high K-storage capacity of 608 mAh g-1 at 100 mA g-1 and stable cycling capacity of 330.6 mAh g-1 at 1000 mA g-1 after 500 cycles are achieved.