ИСТИНА

Lithium-ion batteries (LIBs) exhibit the largest energy/mass ratio and energy/volume ratio among commercial types of batteries. These features, which are extremely useful from the point of view of the operability of portable devices, raise the question of the safety of using such an energy density. Sodium-ion batteries (SIBs) are considered as an alternative to LIBs capable of reducing the price per kilowatt-hour for large-scale applications. They use the same operational principles as LIBs, and the safety issues are even more pressing for SIBs since the average battery size is supposed to vary between several kilowatt-hours and megawatt-hours. It is known that electrochemical properties of cathode materials can be changed by varying their chemical composition. Thus, for sodium layered oxide NaNixFeyMn1–x–yO2, a change in the composition of 3d–metals leads to a change in the average working potential. Increasing manganese content in the layered oxide changes the character of the charge-discharge curve, a plateau appears at 2.25 V, corresponding to the Mn3+/Mn4+ transition [1]. For a material with the NASICON-type structure Na3+xMnxV2-x(PO4)3, increasing the manganese content leads to increasing of the average operating potential and allows to extract additional Na+ ion with additional specific capacity [2]. We expect that a change in the chemical composition will also lead to a change in the thermal stability of materials in a charged form. We have shown that increasing the manganese content of the layered oxide improves its safety under thermal abuse conditions, but for NASICON-type structure increasing the manganese content decrease its thermal stability. This work was supported by the Russian Science Foundation (Grant 17-73-30006) and the Russian Foundation for Basic Research (Young Scientists Grant, Project 20-33-90161).