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.1 Development of the cathode materials for NIB combines studies conducted in two principal directions: oxide and polyanion materials. In the field of anode materials, the main object of study is carbon non-graphitizable materials, so-called "hard carbon". Various vanadium compounds became an object of intensive research and most probable candidates for practical application in NIB due to the rich crystal chemistry of oxide and polyanionic V-based materials and a wide range of redox transitions: V+2 / V+3 / V+4 / V+5.2 In our work, we studied a number of vanadium compounds for use as both cathode and anode materials for NIB. The report will address issues related to the synthesis, electrochemical properties, and phase and structural transformations during Na+ (de)intercalation for a number of vanadium compounds: Na4MnV(PO4)3, β-NaVP2O7, Na3V3(PO4)4, VOCl, etc.