ИСТИНА

Sodium-ion batteries (NIB) are considered as an alternative to lithium-ion batteries (LIB) in a number of applications, e.g. for large-scaled energy storage systems. Various vanadium compounds became an object of intensive research as a materials for NIB due to the rich crystal chemistry of V-based materials and a wide range of redox transitions. In our work, we studied a number of vanadium compounds for use as both cathode and anode materials for NIB. Thus, novel electrode material β-NaVP2O7 with the KAlP2O7-type structure demonstrates attractive electrochemical behaviour as a Na-ion cathode material with reversible capacity of 104 mAh/g. At low voltage region (≈1.5 V vs. Na/Na+), β-NaVP2O7 reversibly intercalates additional sodium cations leading to extraordinary overall Na-ion storage ability exceeding 200 mAh/g. This process is characterized by significant asymmetry between high-voltage and low-voltage plateaus, which is typical for different vanadium-based materials. However, β-LiVP2O7 obtained by electrochemical exchange of Na to Li does not show this asymmetry in Li-cell. The origin of such behaviour is a subject for discussion. Generally, the talk will address issues related to the synthesis, electrochemical properties, thermal stability and phase and structural transformations taking place during Na+ and Li+ (de)intercalation for a several vanadium compounds, mainly Na4V1-xMnx(PO4)3, β-NaVP2O7 and their lithium-contained counterparts, [1],[2]. This work was supported by the Russian Science Foundation (grant. 19-73-10078). [1] M. V. Zakharkin, O. A. Drozhzhin, I. V. Tereshchenko, D. Chernyshov, A. M. Abakumov, E. V. Antipov and K. J. Stevenson, ACS Appl. Energy Mater., 1, 5842–5846 (2018) [2] O. A. Drozhzhin, I. V. Tertov, A. M. Alekseeva, D. A. Aksyonov, K. J. Stevenson, A. M. Abakumov, E. V. Antipov, Chem. Mat. 31, 7463−7469 (2019)