Unraveling the effects of anions in NixAy@CC (A=O, S, P) on Li-sulfur batteries

Nickel-based compounds have been regarded as potential sulfur carriers in Li-sulfur (Li-S) battery. However, the relationship between the anions in those compounds, which are crucial to the intrinsic properties, and their electrochemical performances remains unclear. Herein, nickel compounds with the same morphologies, i.e., Ni5P4, NiO, and NiS, grown on carbon cloths (noted as NixAy@CC (A = O, S, P)) have been rationally designed to act as sulfur hosts in Li-S batteries to investigate the compositional effects on their catalytic activities and chemical absorption abilities. Density functional theory (DFT) results demonstrate that such variations in electrochemical performance are attributed to the interaction between polysulfides (PSs) and nickel compounds, leading to different adsorption energies and interfacial states. Among them, Ni5P4@CC exhibits the best electrochemical performance, delivering capacities of 1349.5, 1020.4, 803.7, 656.7 mAh g−1 at rates of 0.1, 0.5, 2, and 3C, respectively. Moreover, super stable cycling performance has been achieved at 1C and 3C by Ni5P4@CC-based electrode, showing an ultralow decay ratio of 0.0357% and 0.0173% per cycle for over 1000 and 2000 cycles, respectively. In contrast, NiS@CC and NiO@CC show 0.0796% and 0.0787% per cycle at the cycling test.