Interaction between Electrolytes and Sb2O3‐Based Electrodes in Sodium Batteries: Uncovering the 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 Sb2O3 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 Sb2O3 electrode. Sb2O3 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 Sb2O3 during cycling. Diglyme has the ability to coordinate and extract Sb3+ during the oxidation of Sb2O3. 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 Sb2O3 electrodes that can avoid Sb3+ ion dissolution. A critical examination of the electrolyte solutions components' impact is essential to match them with conversion reaction anodes. [ABSTRACT FROM AUTHOR]