Pre-removing partial ammonium ions from the interlayer of ammonium vanadate with acid treating for quasi-solid-state flexible zinc ion batteries

Aqueous zinc ion batteries (AZIBs) have received extensive attention and study owing to environmental protection and intrinsic safety, in which ammonium vanadate (NH4V4O10) with possessing stable bi-layered structure and high theoretical quality capacity is regarded as a potential cathode material. Nevertheless, the excessive ammonium ions located in the interlayer largely limit the Zn2+ diffusion efficiency. Herein, acid treatment was employed to remove part of ammonium ions from the interlayer of NH4V4O10 to prepared NH4+-deficient ammonium vanadate (NVO2), which can enlarge the interlayer distance and enhance the Zn2+ diffusion efficient. The experimental result demonstrates that the NVO2 electrode exhibits a high specific capacity of 472.5 mAh/g at 0.1 A/g and excellent rate performance of 195.5 mAh/g with current density increasing 100 times. Subsequently, some ex-situ characterization methods were utilized to analyze the Zn2+ storage mechanism in NVO2. In addition, flexible NVO2/CNT membrane electrode was prepared by vacuum filtration and further assemble the quasi-solid-state flexible zinc ion batteries with employing polyacrylamide hydrogel, which exhibits a favorable electrochemical performance and mechanical stability as well, revealing its huge application prospect for flexible electronics.