WITHDRAWN: Facile synthesis of monoclinic ammonium vanadate nanoflower and their applications for Aqueous ammonium-ion battery

Abstract

Ammonium ions (NH4+) have gained significant attention in the field of energy storage due to their environmentally friendly nature, abundant resources, and fast diffusion. To improve the electrochemical performance of ammonium vanadate, we implemented a planar spacing approach, resulting in a highly efficient positive electrode material for aqueous ammonium ion batteries. Through our investigations, we successfully synthesized NH4V4O10 with well-controlled planar spacing. This material demonstrated impressive electrochemical properties, including a discharge specific capacity of 297 mAh g-1 at 0.5 A g-1, excellent rate performance with a capacity of 97 mAh g-1 at high current density (10 A g-1), and a large ammonium ion diffusion coefficient ranging from 2.09×10− 6 to 3.66×10− 5 cm2 S-1. To further enhance its practical application, we combined NH4V4O10 with polyaniline to assemble an aqueous ammonium ion full cell, achieving a high specific capacity of 88 mAh g-1 at 0.5 A g-1 and a remarkable energy density of 88 Wh kg-1 (at a power density of 500 W kg-1). In-situ electrochemical tests revealed that NH4V4O10 undergoes a phase transition to (NH4)1.92V3O8 during the first discharge process, and reversible hydrogen bond formation/breaking occurs during the ammoniation/deamination process. Moreover, our study successfully synthesized planar-spaced ammonium vanadate and highlights its exceptional electrochemical performance as a positive electrode material for aqueous ammonium ion batteries. The mechanistic insights gained from this study contribute to a deeper understanding of the behavior of ammonium vanadate within various structural frameworks.