Nickel single atom overcoordinated active sites to accelerate the electrochemical reaction kinetics for Li-S cathode

Lithium-sulfur (Li-S) batteries with high theoretical energy density are promising advanced energy storage devices. However, shuttling of dissolute lithium polysulfide (LiPSs) and sluggish conversion kinetics impede their applications. Herein, single nickel (Ni) atoms on two-dimensional (2D) nitrogen(N)-doped carbon with Ni-N4-O overcoordinated structure (SANi-N4-O/NC) are prepared and firstly used as a sulfur host of Li-S batteries. Due to the efficient polysulfides traps and highly LiPSs conversion effect of SANi-N4-O/NC, the electrochemical performance of Li-S batteries obviously improved. The batteries can well operate even under high sulfur loading (5.8 mg cm−2) and lean electrolyte (6.1 μL mg−1) condition. Meanwhile, density functional theory (DFT) calculations demonstrate that Ni single atom's active sites decrease the energy barriers of conversion reactions from Li2S8 to Li2S due to the strong interaction between SANi-N4-O/NC and LiPSs. Thus, the kinetic conversion of LiPSs was accelerated and the shuttle effect is suppressed on SANi-N4-O/NC host. This study provides a new design strategy for a 2D structure with single-atom overcoordinated active sites to facilitate the fast kinetic conversion of LiPSs for Li-S cathode.