Ammonium vanadate doped by transition bivalent metal ions for high-performance zinc-ion batteries

Abstract

Vanadium-based materials are considered as promising cathode materials in aqueous zinc-ion (Zn2+) batteries (AZIBs) because of their abundant valence states and adjustable ion diffusion channels. However, the slow kinetics of the Zn2+ intercalation and the instability of the layered structure during long cycle are the bottlenecks restricting their further development. In this paper, the transition bivalent manganese ions (Mn2+) are introduced into ammonium vanadate (NH4V4O10) to partly replace the NH4+ ions to prepare a high-performance AZIB cathode. After doping transition bivalent Mn2+, the interlayer spacing of NH4V4O10 is enlarged, providing a broadened channel for the diffusion of Zn2+ accordingly. The results reveal that the electrode with the optimal doping quantity has a very high discharge capacity (539.4 mAh/g at 0.2 A/g) and excellent cyclic stability (85.3 % retention of the initial capacity after 3000 cycles at 5 A/g). A highly competitive energy density of 378 Wh kg−1 at 362 W kg−1 is delivered by the corresponding AZIB. Moreover, this method is a general and effective strategy for developing high-performance AZIB cathode materials, as demonstrated by the consistent crystal structure and stable cycling properties for NH4V4O10 doped with other transition bivalent metal cations.