The Interaction Between Electrolytes and Sb2O3–based Electrodes in Sodium Batteries: Uncovering Detrimental Effects of Diglyme

Conversion materials are promising to improve the energy density of sodium‐ion‐batteries (NIB). Nevertheless, they suffer from the drawback of phase transitions and pronounced volume changes during cycling, which causes cell instability. When using these types of electrodes, all cell‐components have to be adjusted. In this study, a tremendous influence of the electrolyte solution on Sb$_{2}$O$_{3}$ conversion electrodes for NIBs is discussed. Solutions based on three solvents and solvent combinations established for NIBs, ethylene carbonate/dimethyl carbonate (EC/DMC), EC/DMC+5 % fluoroethylene carbonate (FEC), and diglyme, lead to a massively divergent electrochemical behavior of the same Sb$_{2}$O$_{3}$ electrode. Sb$_{2}$O$_{3}$ demonstrates the highest stability in solutions containing FEC, because this component forms a flexible, protecting surface film that prevent disintegration. One key finding of this work is that electrolyte solutions based on ether solvents like diglyme can remove Sb‐ions from Sb$_{2}$O$_{3}$ during cycling. Diglyme has the ability to coordinate and extract Sb$^{3+}$ during the oxidation of Sb$_{2}$O$_{3}$. This leads to contaminations of all cell components and a strong capacity loss together with an irregular electrochemical signature. Due to its poor reactivity at low potentials, diglyme forms a thin or even no surface layer. Thereby, there are no protecting films on the Sb$_{2}$O$_{3}$ electrodes that can avoid Sb$^{3+}$ ion dissolution. A critical examination of the electrolyte solutions components’ impact is essential to match them with conversion reaction anodes.