Synergetic Effect of Alkali-Site Substitution and Oxygen Vacancy Boosting Vanadate Cathode for Super-Stable Potassium and Zinc Storage

Layer-structured metal vanadates have attracted extensive attention as cathode materials due to multi-electron redox reactions and versatile cations storage capability. Nevertheless, their actual promotion is still hindered by the sluggish reaction kinetics and inferior phase transition upon repeated cations (de)intercalation. Here, large-sized NH4+ is introduced into the K-site of K-0.43(NH4)(0.12)V2O5-delta to enable more kinetically favorable oxygen vacancies. The reinforced structure ensures complete solid-solution phase transition and buffers the dramatic structural change upon potassium storage. The stable presence of NH4+ as pillars during cycling is also confirmed. Meanwhile, the oxygen vacancies induced by alkali-site substitution can facilitate ion diffusion and enhance the electronic conductivity, as further demonstrated by theoretical calculations. Therefore, it exhibits a high capacity of 117.8 mA g(-1) at 20 mA g(-1) with smooth profiles and superior capacity retention of 92.5% after 800 cycles at 1000 mA g(-1). Such an effective synergetic strategy also promotes its zinc storage capability, which performs negligible self-discharge behavior and retains a reversible capacity of 216.8 mAh g(-1) after 3000 cycles at 10 A g(-1). This synergetic strategy may provide novel perspectives to develop layer-structured cathode and facilitate its practical application in energy storage devices.

Automated summary

Layer-structured metal vanadates have been studied as cathode materials due to their redox reactions and cations storage capability. The study introduces large-sized NH4+ ions to enhance the oxygen vacancies and improve the reaction kinetics. This approach significantly improves the capacity and cycling performance of the cathode material. In addition, the study investigates the role of oxygen vacancies in ion diffusion and electronic conductivity. This research provides new insights for the development and practical application of layer-structured cathode materials in energy storage devices.