Layered ferric vanadate nanosheets as a high-rate NH4+ storage electrode

Abstract

ABSTRACT Aqueous rechargeable batteries hold the potential for the application in large-scale energy storage system due to low cost, environmentally friendliness, and high safety. In the past several decades, tremendous research efforts have been devoted to the batteries with metal ions as charge carriers. However, little attention is paid to the non-metal charge carriers, such as ammonium ions. In this work, layered iron vanadate nanosheets are first introduced as ammonium ion storage electrode. In comparison with the Na+ and K+ storage performance, iron vanadate nanosheets show a much improved pseudocapacitance behavior with NH4+ as charge carriers. In this way, at the high current density of 5 A/g, the FVO nanosheets in aqueous (NH4)2SO4 electrolyte display the highest specific capacity of 72.5 mAh/g for 500 cycles, compared with the FVO nanosheets in Na2SO4 (64.7 mAh/g) and K2SO4 (17.3 mAh/g). The difference is attributed to the dirctional H-bondings between the intercalated NH4+ ions and the host iron vanadate nanosheets. This work provides a new direction to expand aqueous batteries with ammonium ion as charger carriers.