Abstract

Due to the structural diversity and chemical activity, vanadium oxides and their derivatives are continuingly in the great interest of scientist. In a large family of vanadium compounds, one of the most interesting are ammonium vanadates (with the general formula (NH4)xVyOz). They have received much attention because of their promising application as cathode material in mono- and multivalent-ion batteries [1]. Hydrothermal synthesis is already established as an efficient method to produce ammonium vanadates with various morphology, structure and chemical composition. The aforementioned parameters determined the electrochemical properties of the material and could be tailored by varying synthesis parameters (e.g. temperature, time, pH) [2]. In presented work, the effect of the initial hydrothermal synthesis pressure on the final product was studied for the first time. All samples were prepared via hydrothermal method in the autoclave, in which the water solution of NH4VO3 and C2H2O4 was heated to 180°C for 8h. In order to study the pressure effect, the same procedure was repeated without the initial pressure and with pre-pressurized the autoclave to 5, 25, 50 bars. The obtained samples were fully characterized with SEM, TEM, XRD, XPS, FTIR and TGA. Results indicate that the initial pressure affects both the morphology and the structure of samples and cannot be neglected in the synthesis. Moreover, the electrochemical performance of the as-prepared samples as lithium-ion cathode materials were investigated. It was found that sample obtained with higher pressure exhibit higher specific capacity and cyclic stability. FIGURE 1. Comparison of ammonium vanadates obtained with different initial hydrothermal synthesis pressure. Acknowledgements Part of this work was supported by the National Science Centre (No. 2017/01/X/ST5/01415). References [1] Y. Liu et al.J., Mater. Sci., 53(3),pp. 2045–2053, 2018 [2] S. Sarkar et al., Electrochim. Acta, vol. 132, pp. 448–456, 2014.

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