Core-shell structural vanadium Oxide/Polypyrrole anode for aqueous Ammonium-Ion batteries

Aqueous ammonium-ion batteries (AAIBs) are attracting attention, mainly due to the unique interaction between NH4+ and the host materials. Yet, few studies focus on the development of high-performance anode materials for NH4+ storage, hindering the applications of AAIBs. Herein, we study the electrochemical NH4+ storage properties of an electrodeposited vanadium oxide/polypyrrole (VOx@PPy) electrode with a core–shell structure. The strong interaction between PPy and VOx enhances the electrochemical performance of the composite electrode. The electrons in N atoms from PPy are attracted by V cations from VOx, resulting in the enhanced protonation level of PPy and the reduction of V in the composite material. Therefore, VOx@PPy exhibits a high specific capacity of 195.36 mAh/g at 0.2 A/g in ammonium acetate electrolyte, outperforming other reported anode materials for NH4+ storage. In addition, the conformal PPy coating can efficiently suppress VOx dissolution, leading to good cycling stability for VOx@PPy. We assembled an aqueous ammonium-ion battery using VOx@PPy as the anode. The device exhibits a good energy density of 74.1 Wh kg−1 at the power density of 75.6 W kg−1. This work highlights the advantages of the hybrid organic/inorganic materials for NH4+ storage and could push the development of aqueous ammonium-ion batteries.