Lithium-ion batteries remain the main source of energy storage today, however, they have significant disadvantages associated with their explosiveness due to the use of organic electrolytes. Metal-ion batteries with water-based electrolytes, in particular zinc-ion batteries, are gaining more and more attention due to their advantages such as environmental friendliness, safety and lower price compared to lithium-ion batteries.
The issue of choice the cathode material for zinc-ion batteries is the most important for ensuring high capacitive characteristics of the battery and stability during long cycling. Layered metal oxides, especially vanadium ones, demonstrate good electrochemical performance because of reversible zinc intercalation in their crystal lattices. Vanadium(V) oxide is expected to have the highest theoretical capacity (589 mAh/g) due to the two-electron reaction [1]. Nevertheless, due to its drawbacks like long activation process and insufficient stability, it needs to improve it [2]. The introduction of alkali metal ions into the layered structure of vanadium oxide can increase the interlayer distances, which gives the stability and faster intercalation/deintercalation kinetics of Zn2+ [3].
M-doped V2O5 (M = Li, Na, K, Cs) was obtained as a result of a two-step synthesis. At the first stage, the corresponding alkali metal metavanadates were synthesized by mixing equimolar weights of V2O5 and alkali metal carbonates M2CO3 in water solution with subsequent boiling. In the second stage, MVO3 was mixed with VOSO4∙xH2O in a molar ratio of 1:2 (pH = 3-4) in an aqueous solution and transferred in an autoclave at 180 °C for 5 days [4]. The obtained black powder was washed with water, ethanol and dried at room temperature.
The resulting powders were characterized by X-ray diffraction (XRD). The structure was established by scanning electron microscopy. Electrochemical measurements (galvanostatic cycling, cyclic voltammetry) were performed in aqueous 3 M ZnSO4 in the potential range of 0.3–1.5 V (vs. Zn/Zn2+).
Acknowledgements: The financial support from RFBR (grant № 21-53-53012) is gratefully acknowledged. The authors would like to thank the Research Park of Saint Petersburg State University: 1) the Center for X-ray Diffraction Methods, 2) the Interdisciplinary Center for Nanotechnology.