Ultrastable Cu 2+ 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 Cu ²⁺ intercalation chemistry in mass-produced exfoliated NbS ₂ nanosheets to build ultralong lifespan aqueous batteries with cost advantages. Anisotropic interplanar expansion of NbS ₂ lattices balanced dynamic Cu ²⁺ incorporation and the highly reversible redox reaction of Nb ⁴⁺ /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 NbS ₂ ||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.