Tuning the kinetics of binder-free ammonium vanadate cathode via defect modulation for ultrastable rechargeable zinc ion batteries

Highlights: • A novel oxygen defect-rich binder-free cistern-like (NH₄)₂V₁₀O₂₅·8H₂O was prepared. • The O_d-NVO-SS-2 cathode delivers high capacities and excellent long cycle stability. • DFT calculations confirmed that defect can adjust the Zn²⁺ ions adsorption energy and improve the conductivity. • The O_d-NVO-SS-2 is also a potential electrode material for quasi-solid-state ZIBs. Reasonable nanostructure design and proper interface engineering are of great significance for improve the low conductivity and slow kinetic process of vanadium-based compounds. Herein, we report an advanced stainless steel (SS) supported oxygen-rich vacancy (NH₄)₂V₁₀O₂₅·8H₂O (O_d-NVO-SS-2) cistern-like nanobelt cathode with broadened interlayer spacings and ultrafast reaction kinetic. As expected, as cathode of aqueous zinc-ion battery (AZIB), the O_d-NVO-SS-2 electrode shows high capacity of 331.4 mAh g⁻¹ (0.3 A g⁻¹), excellent rate performance and satisfactory cyclic stability (78.3 mAh g⁻¹ at 4.8 A g⁻¹ after 7500 cycles). In addition, a flexible quasi-solid-state (FQSS) O_d-NVO-SS-2//Zn battery was studied, which showed almost the same excellent performance in various bending states, and even in a variety of harsh conditions water immersion, hammering, washing, loading, drilling and cutting, it can also perform well. In this work, the projected density of states (PDOS) calculation results shows that the defects improve the conductivity due to the increase of carrier concentration, which is beneficial to improve the reaction kinetics and endow the ability to store Zn²⁺ ions rapidly. The smaller Zn²⁺ ion adsorption energy of O_d-NVO-SS-2 calculated by density functional theory (DFT) also indicates that the introduction of defects is conducive to increasing the active sites of electrode materials and contributing additional capacity. In addition, that active material is directly grown on the current collector, thereby effectively avoiding shedding in the circulation process. Importantly, the Zn²⁺ storage mechanism in O_d-NVO-SS-2 is successfully revealed. This defect engineering has reference significance for the design of advanced electrode materials with excellent properties.