Dual-engineering of ammonium vanadate for enhanced aqueous and quasi-solid-state zinc ion batteries

Ammonium vanadate holds promise for the high-performance cathode in aqueous zinc ion batteries (ZIBs) due to its stable layered structure and superior theoretical capacity. However, excessive ammonium cations occupying the interlayer and too strong electrostatic interaction between Zn 2+ and defect-free V-O bonds largely hinder the capacity and rate performance of ammonium vanadate in ZIBs. Here, in this work, a dual-engineering method that integrates the partial removal of ammonium cations and the increase of oxygen vacancies has been proposed to boost the performance of NH 4 V 4 O 10 (NVO). Experimental evidence and theoretical calculations demonstrate that this method can ensure an enlarged room for the (de)intercalation of more Zn 2+ ions and weaken the strong electrostatic interaction between the V-O layer and Zn 2+ to reduce the energy barrier of the Zn 2+ diffusion process. As a consequence, the specific capacity of the as-obtained NVO with the above dual characteristic (NVO-300) was enhanced from 304 mAh g − 1 to 355 mAh g − 1 , relative to the NVO without dual characteristic. And the rate capability of NVO-300 has a more than 300% increase relative to NVO. Furthermore, benefiting from the superior performance and self-supporting feature of this NVO-300, a quasi-solid-state ZIB based on NVO-300 displays a satisfactory specific capacity of 307 mAh g − 1 at 0.5 A g − 1 and a high energy density of 214 Wh kg −1 at 345 W kg −1 , demonstrative of its great usage potential as a practical portable energy storage device.