Enabling High-Loading Aqueous Zinc–Sulfur Batteries Via a Ni Single-Atom Catalytic Host with Hierarchical Sulfur Reservoirs

Abstract

Aqueous zinc–sulfur batteries have drawn considerable interest owing to their high theoretical capacity, intrinsic safety, and cost-effectiveness. Nevertheless, the sulfur cathode typically exhibits sluggish two-electron solid-state conversion reactions, resulting in a lower discharge voltage and inefficient sulfur utilization. Herein, we design a nickel single-atom-anchored on N-doped carbon hollow structure featuring an internal three-dimensional network-like skeleton as the sulfur host to address these issues. The nickel single-atom-anchored on N-doped carbon hollow structure synergistically combines atomic Ni-N₄ catalytic sites as well as a hollow structure possessing a high specific surface area and hierarchical nanopores. Consequently, the resulting S@Ni-SAs/NCHS achieves a high sulfur loading of ~74 wt% and a specific capacity of 1664.6 mAh g⁻¹ at 0.1 A g⁻¹ with a low polarization of 0.35 V. Besides, it maintains a capacity of 1154.4 mAh g⁻¹ at 5 A g⁻¹ and shows a retained capacity of 1038.6 mAh g⁻¹ after 1000 cycles at 2 A g⁻¹, which corresponds to a decay rate of 0.03% per cycle. Density functional theory calculations reveal that the Ni-N₄ site serves as an efficient electron donor, facilitating charge transfer and reducing the energy barrier of the rate-determining step from 1.845 eV to 1.458 eV. Furthermore, a pouch cell with a high areal sulfur loading demonstrates specific capacities of 1200–1400 mAh g⁻¹ under various bending states with discharge plateaus about 0.8 V, retaining 83.4% capacity after 200 cycles. This work underscores the critical role of integrating Ni atomic catalysis with well-developed porosity within the carbon hollow structure for developing high-performance aqueous zinc–sulfur batteries.