Ultrastable Cu2+ Intercalation Chemistry Based on a Niobium Sulfide Nanosheet Cathode for Advanced Aqueous Storage Devices.

Exploring stable and durable cathodes for cost-effective reversible aqueous batteries is highly desirable for grid-scale energy storage applications, but significant challenges remain. Herein, we disclosed an ultrastable Cu2+ intercalation chemistry in mass-produced exfoliated NbS2 nanosheets to build ultralong lifespan aqueous batteries with cost advantages. Anisotropic interplanar expansion of NbS2 lattices balanced dynamic Cu2+ incorporation and the highly reversible redox reaction of Nb4+/Nb(4-δ)+ couple were illuminated by operando synchrotron X-ray diffraction and energy dispersive X-ray absorption spectroscopy, affording an extraordinary capacity of approximately 317 mAh g-1 at 1 A g-1 and a good stability of 92.2% capacity retention after 40000 cycles at 10 A g-1. Impressively, a budget NbS2||Fe hybrid ion cell involving an aqueous electrolyte/Fe-metal anode is established and provides a reliable energy supply of 225.4 Wh kg-1 at 750 W kg-1, providing insights for building advanced aqueous battery systems for large-scale applications.